Implement canonical formatter (#1107)

CLI commands also added: `pkl format check` and `pkl format apply`.

pkl-formatter/gradle.lockfile

@@ -0,0 +1,36 @@
+# This is a Gradle generated file for dependency locking.
+# Manual edits can break the build and are not advised.
+# This file is expected to be part of source control.
+net.bytebuddy:byte-buddy:1.15.11=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.apiguardian:apiguardian-api:1.1.2=testCompileClasspath,testImplementationDependenciesMetadata
+org.assertj:assertj-core:3.27.3=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.jetbrains.intellij.deps:trove4j:1.0.20200330=kotlinBuildToolsApiClasspath,kotlinCompilerClasspath,kotlinKlibCommonizerClasspath
+org.jetbrains.kotlin:kotlin-build-common:2.0.21=kotlinBuildToolsApiClasspath
+org.jetbrains.kotlin:kotlin-build-tools-api:2.0.21=kotlinBuildToolsApiClasspath
+org.jetbrains.kotlin:kotlin-build-tools-impl:2.0.21=kotlinBuildToolsApiClasspath
+org.jetbrains.kotlin:kotlin-compiler-embeddable:2.0.21=kotlinBuildToolsApiClasspath,kotlinCompilerClasspath,kotlinKlibCommonizerClasspath
+org.jetbrains.kotlin:kotlin-compiler-runner:2.0.21=kotlinBuildToolsApiClasspath
+org.jetbrains.kotlin:kotlin-daemon-client:2.0.21=kotlinBuildToolsApiClasspath
+org.jetbrains.kotlin:kotlin-daemon-embeddable:2.0.21=kotlinBuildToolsApiClasspath,kotlinCompilerClasspath,kotlinKlibCommonizerClasspath
+org.jetbrains.kotlin:kotlin-klib-commonizer-embeddable:2.0.21=kotlinKlibCommonizerClasspath
+org.jetbrains.kotlin:kotlin-native-prebuilt:2.0.21=kotlinNativeBundleConfiguration
+org.jetbrains.kotlin:kotlin-reflect:2.0.21=kotlinBuildToolsApiClasspath,kotlinCompilerClasspath,kotlinKlibCommonizerClasspath
+org.jetbrains.kotlin:kotlin-script-runtime:2.0.21=kotlinBuildToolsApiClasspath,kotlinCompilerClasspath,kotlinCompilerPluginClasspathMain,kotlinCompilerPluginClasspathTest,kotlinKlibCommonizerClasspath
+org.jetbrains.kotlin:kotlin-scripting-common:2.0.21=kotlinBuildToolsApiClasspath,kotlinCompilerPluginClasspathMain,kotlinCompilerPluginClasspathTest
+org.jetbrains.kotlin:kotlin-scripting-compiler-embeddable:2.0.21=kotlinBuildToolsApiClasspath,kotlinCompilerPluginClasspathMain,kotlinCompilerPluginClasspathTest
+org.jetbrains.kotlin:kotlin-scripting-compiler-impl-embeddable:2.0.21=kotlinBuildToolsApiClasspath,kotlinCompilerPluginClasspathMain,kotlinCompilerPluginClasspathTest
+org.jetbrains.kotlin:kotlin-scripting-jvm:2.0.21=kotlinBuildToolsApiClasspath,kotlinCompilerPluginClasspathMain,kotlinCompilerPluginClasspathTest
+org.jetbrains.kotlin:kotlin-stdlib-jdk7:2.0.21=apiDependenciesMetadata,compileClasspath,implementationDependenciesMetadata,runtimeClasspath,testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.jetbrains.kotlin:kotlin-stdlib-jdk8:2.0.21=apiDependenciesMetadata,compileClasspath,implementationDependenciesMetadata,runtimeClasspath,testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.jetbrains.kotlin:kotlin-stdlib:2.0.21=apiDependenciesMetadata,compileClasspath,implementationDependenciesMetadata,kotlinBuildToolsApiClasspath,kotlinCompilerClasspath,kotlinCompilerPluginClasspathMain,kotlinCompilerPluginClasspathTest,kotlinKlibCommonizerClasspath,runtimeClasspath,testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.6.4=kotlinBuildToolsApiClasspath,kotlinCompilerClasspath,kotlinKlibCommonizerClasspath
+org.jetbrains:annotations:13.0=compileClasspath,kotlinBuildToolsApiClasspath,kotlinCompilerClasspath,kotlinCompilerPluginClasspathMain,kotlinCompilerPluginClasspathTest,kotlinKlibCommonizerClasspath,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
+org.junit.jupiter:junit-jupiter-api:5.13.0=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.junit.jupiter:junit-jupiter-engine:5.13.0=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.junit.jupiter:junit-jupiter-params:5.13.0=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.junit.platform:junit-platform-commons:1.13.0=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.junit.platform:junit-platform-engine:1.13.0=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.junit.platform:junit-platform-launcher:1.13.0=testRuntimeClasspath
+org.junit:junit-bom:5.13.0=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+org.opentest4j:opentest4j:1.3.0=testCompileClasspath,testImplementationDependenciesMetadata,testRuntimeClasspath
+empty=annotationProcessor,compileOnlyDependenciesMetadata,intransitiveDependenciesMetadata,kotlinCompilerPluginClasspath,kotlinNativeCompilerPluginClasspath,kotlinScriptDefExtensions,sourcesJar,testAnnotationProcessor,testApiDependenciesMetadata,testCompileOnlyDependenciesMetadata,testIntransitiveDependenciesMetadata,testKotlinScriptDefExtensions

pkl-formatter/pkl-formatter.gradle.kts

@@ -0,0 +1,48 @@
+/*
+ * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+plugins {
+  pklAllProjects
+  pklKotlinLibrary
+  pklPublishLibrary
+}
+
+dependencies {
+  api(projects.pklParser)
+
+  testImplementation(projects.pklCommonsTest)
+}
+
+tasks.test {
+  inputs
+    .dir("src/test/files/FormatterSnippetTests/input")
+    .withPropertyName("formatterSnippetTestsInput")
+    .withPathSensitivity(PathSensitivity.RELATIVE)
+  inputs
+    .dir("src/test/files/FormatterSnippetTests/output")
+    .withPropertyName("formatterSnippetTestsOutput")
+    .withPathSensitivity(PathSensitivity.RELATIVE)
+}
+
+publishing {
+  publications {
+    named<MavenPublication>("library") {
+      pom {
+        url.set("https://github.com/apple/pkl/tree/main/pkl-formatter")
+        description.set("Formatter for Pkl")
+      }
+    }
+  }
+}

pkl-formatter/src/main/kotlin/org/pkl/formatter/Formatter.kt

@@ -0,0 +1,53 @@
+/*
+ * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.formatter
+
+import java.nio.file.Files
+import java.nio.file.Path
+import org.pkl.formatter.ast.ForceLine
+import org.pkl.formatter.ast.Nodes
+import org.pkl.parser.GenericParser
+
+/** A formatter for Pkl files that applies canonical formatting rules. */
+class Formatter {
+  /**
+   * Formats a Pkl file from the given file path.
+   *
+   * @param path the path to the Pkl file to format
+   * @return the formatted Pkl source code as a string
+   * @throws java.io.IOException if the file cannot be read
+   */
+  fun format(path: Path): String {
+    return format(Files.readString(path))
+  }
+
+  /**
+   * Formats the given Pkl source code text.
+   *
+   * @param text the Pkl source code to format
+   * @return the formatted Pkl source code as a string
+   */
+  fun format(text: String): String {
+    val parser = GenericParser()
+    val builder = Builder(text)
+    val gen = Generator()
+    val ast = parser.parseModule(text)
+    val formatAst = builder.format(ast)
+    // force a line at the end of the file
+    gen.generate(Nodes(listOf(formatAst, ForceLine)))
+    return gen.toString()
+  }
+}

pkl-formatter/src/main/kotlin/org/pkl/formatter/Generator.kt

@@ -0,0 +1,149 @@
+/*
+ * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.formatter
+
+import org.pkl.formatter.ast.Empty
+import org.pkl.formatter.ast.ForceLine
+import org.pkl.formatter.ast.ForceWrap
+import org.pkl.formatter.ast.FormatNode
+import org.pkl.formatter.ast.Group
+import org.pkl.formatter.ast.IfWrap
+import org.pkl.formatter.ast.Indent
+import org.pkl.formatter.ast.Line
+import org.pkl.formatter.ast.MultilineStringGroup
+import org.pkl.formatter.ast.Nodes
+import org.pkl.formatter.ast.Space
+import org.pkl.formatter.ast.SpaceOrLine
+import org.pkl.formatter.ast.Text
+import org.pkl.formatter.ast.Wrap
+
+internal class Generator {
+  private val buf: StringBuilder = StringBuilder()
+  private var indent: Int = 0
+  private var size: Int = 0
+  private val wrapped: MutableSet<Int> = mutableSetOf()
+  private var shouldAddIndent = false
+
+  fun generate(node: FormatNode) {
+    node(node, Wrap.DETECT)
+  }
+
+  private fun node(node: FormatNode, wrap: Wrap) {
+    when (node) {
+      is Empty -> {}
+      is Nodes -> node.nodes.forEach { node(it, wrap) }
+      is Group -> {
+        val width = node.nodes.sumOf { it.width(wrapped) }
+        val wrap =
+          if (size + width > MAX) {
+            wrapped += node.id
+            Wrap.ENABLED
+          } else {
+            Wrap.DETECT
+          }
+        node.nodes.forEach { node(it, wrap) }
+      }
+      is ForceWrap -> {
+        wrapped += node.id
+        val wrap = Wrap.ENABLED
+        node.nodes.forEach { node(it, wrap) }
+      }
+      is IfWrap -> {
+        if (wrapped.contains(node.id)) {
+          node(node.ifWrap, Wrap.ENABLED)
+        } else {
+          node(node.ifNotWrap, wrap)
+        }
+      }
+      is Text -> text(node.text)
+      is Line -> {
+        if (wrap.isEnabled()) {
+          newline()
+        }
+      }
+      is ForceLine -> newline()
+      is SpaceOrLine -> {
+        if (wrap.isEnabled()) {
+          newline()
+        } else {
+          text(" ")
+        }
+      }
+      is Space -> text(" ")
+      is Indent -> {
+        if (wrap.isEnabled() && node.nodes.isNotEmpty()) {
+          size += INDENT.length
+          indent++
+          node.nodes.forEach { node(it, wrap) }
+          indent--
+        } else {
+          node.nodes.forEach { node(it, wrap) }
+        }
+      }
+      is MultilineStringGroup -> {
+        val indentLength = indent * INDENT.length
+        val offset = (indentLength + 1) - node.endQuoteCol
+        var previousNewline = false
+        for ((i, child) in node.nodes.withIndex()) {
+          when {
+            child is ForceLine -> newline(shouldIndent = false) // don't indent
+            child is Text &&
+              previousNewline &&
+              child.text.isBlank() &&
+              child.text.length == indentLength &&
+              node.nodes[i + 1] is ForceLine -> {}
+            child is Text && previousNewline && offset != 0 -> text(reposition(child.text, offset))
+            else -> node(child, Wrap.DETECT) // always detect wrapping
+          }
+          previousNewline = child is ForceLine
+        }
+      }
+    }
+  }
+
+  private fun text(value: String) {
+    if (shouldAddIndent) {
+      repeat(times = indent) { buf.append(INDENT) }
+      shouldAddIndent = false
+    }
+    size += value.length
+    buf.append(value)
+  }
+
+  private fun newline(shouldIndent: Boolean = true) {
+    size = INDENT.length * indent
+    buf.append('\n')
+    shouldAddIndent = shouldIndent
+  }
+
+  private fun reposition(text: String, offset: Int): String {
+    return if (offset > 0) {
+      " ".repeat(offset) + text
+    } else {
+      text.drop(-offset)
+    }
+  }
+
+  override fun toString(): String {
+    return buf.toString()
+  }
+
+  companion object {
+    // max line length
+    const val MAX = 100
+    private const val INDENT = "  "
+  }
+}

pkl-formatter/src/main/kotlin/org/pkl/formatter/NaturalOrderComparator.kt

@@ -0,0 +1,66 @@
+/*
+ * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.formatter
+
+internal class NaturalOrderComparator(private val ignoreCase: Boolean = false) :
+  Comparator<String> {
+
+  override fun compare(s1: String, s2: String): Int {
+    var i = 0
+    var j = 0
+
+    while (i < s1.length && j < s2.length) {
+      val c1 = if (ignoreCase) s1[i].lowercaseChar() else s1[i]
+      val c2 = if (ignoreCase) s2[j].lowercaseChar() else s2[j]
+
+      if (c1.isDigit() && c2.isDigit()) {
+        val (num1, nextI) = getNumber(s1, i)
+        val (num2, nextJ) = getNumber(s2, j)
+
+        val numComparison = num1.compareTo(num2)
+        if (numComparison != 0) {
+          return numComparison
+        }
+        i = nextI
+        j = nextJ
+      } else {
+        val charComparison = c1.compareTo(c2)
+        if (charComparison != 0) {
+          return charComparison
+        }
+        i++
+        j++
+      }
+    }
+
+    return s1.length.compareTo(s2.length)
+  }
+
+  private fun getNumber(s: String, startIndex: Int): LongAndInt {
+    var i = startIndex
+    val start = i
+
+    while (i < s.length && s[i].isDigit()) {
+      i++
+    }
+    val numStr = s.substring(start, i)
+    val number = numStr.toLongOrNull() ?: 0L
+    return LongAndInt(number, i)
+  }
+
+  // use this instead of Pair to avoid boxing
+  private data class LongAndInt(val l: Long, var i: Int)
+}

pkl-formatter/src/main/kotlin/org/pkl/formatter/ast/FormatNode.kt

@@ -0,0 +1,66 @@
+/*
+ * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.formatter.ast
+
+import org.pkl.formatter.Generator
+
+enum class Wrap {
+  ENABLED,
+  DETECT;
+
+  fun isEnabled(): Boolean = this == ENABLED
+}
+
+sealed interface FormatNode {
+  fun width(wrapped: Set<Int>): Int =
+    when (this) {
+      is Nodes -> nodes.sumOf { it.width(wrapped) }
+      is Group -> nodes.sumOf { it.width(wrapped) }
+      is Indent -> nodes.sumOf { it.width(wrapped) }
+      is ForceWrap -> nodes.sumOf { it.width(wrapped + id) }
+      is IfWrap -> if (id in wrapped) ifWrap.width(wrapped) else ifNotWrap.width(wrapped)
+      is Text -> text.length
+      is SpaceOrLine,
+      is Space -> 1
+      is ForceLine,
+      is MultilineStringGroup -> Generator.MAX
+      else -> 0
+    }
+}
+
+data class Text(val text: String) : FormatNode
+
+object Empty : FormatNode
+
+object Line : FormatNode
+
+object ForceLine : FormatNode
+
+object SpaceOrLine : FormatNode
+
+object Space : FormatNode
+
+data class Indent(val nodes: List<FormatNode>) : FormatNode
+
+data class Nodes(val nodes: List<FormatNode>) : FormatNode
+
+data class Group(val id: Int, val nodes: List<FormatNode>) : FormatNode
+
+data class ForceWrap(val id: Int, val nodes: List<FormatNode>) : FormatNode
+
+data class MultilineStringGroup(val endQuoteCol: Int, val nodes: List<FormatNode>) : FormatNode
+
+data class IfWrap(val id: Int, val ifWrap: FormatNode, val ifNotWrap: FormatNode) : FormatNode

pkl-formatter/src/test/files/FormatterSnippetTests/input/class-bodies.pkl

@@ -0,0 +1,10 @@
+class Foo {
+
+}
+
+class Bar
+{
+  qux = 1
+}
+
+class Baz { prop = 0; prop2 = 1 }

pkl-formatter/src/test/files/FormatterSnippetTests/input/comma-termination.pkl

@@ -0,0 +1,16 @@
+function fun(a, b, c, d) = a
+
+noTrailingCommas = fun(1, 2, 3, 4,)
+
+trailingCommas = fun("loooooooooooooooooooongString", "loooooooooooooooongString", "looooooooooooooooongString", "notTooLong")
+
+noTrailingCommaObjParams {
+  fooooooooooooooooooooooooooooooooo, baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaar, baaaaaaaaaaaaaaaaaaaaaz ->
+  1 + 1
+}
+
+trailingCommaInLambdas = (fooooooooooooooooooooooooooooooooo, baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaar, baaaaaaaaaaaaaaaaaaaaaz) -> 1
+
+trailingCommaInConstraints: String(isSomethingSomethingSomething, isSomethingElse, isSomethingSomethingSomethingElse)
+
+trailingCommaInTypeParameters: Mapping<SomethingSomethingSomethingSomething, SomethingSomething | SomethingElse>

pkl-formatter/src/test/files/FormatterSnippetTests/input/comment-interleaved.pkl

@@ -0,0 +1,31 @@
+module comment.interleaved
+
+local test: Int|String =
+  if (true)
+    1 // It's the same as "100%"
+  else
+    "8%"
+
+foo: ( // some comment
+  * String(
+      // if dtstart is defined and a datetime, until must also be a datetime if defined
+      true
+    )
+  |Int
+  // trailing comment
+  )?
+
+foo2: (// some comment
+  Int, // other comment
+    String
+  ) ->Int
+
+bar = ( // some comment
+  10 + 10
+  // another comment
+  )
+
+bar2 = ( // some comment
+    foo, bar
+    // another comment
+  ) -> foo + bar

pkl-formatter/src/test/files/FormatterSnippetTests/input/dangling-doc-comment.pkl

@@ -0,0 +1,8 @@
+module dangling
+
+/// Doc comment.
+///
+/// for this field
+// sepearted by a stray comment
+/// but continues here.
+some: String

pkl-formatter/src/test/files/FormatterSnippetTests/input/doc-comments.pkl

@@ -0,0 +1,14 @@
+
+//// line 1
+///// line 2
+foo = 1
+
+/// line 1
+///      
+/// 
+/// line 2
+bar = 1
+
+///line 1
+///line 2
+baz = 1

pkl-formatter/src/test/files/FormatterSnippetTests/input/expr-binary.pkl

@@ -0,0 +1,25 @@
+foo {
+  123123123123 + 123123123123 * 123123123123 - 123123123123 / 123123123123 + 123123123123 ** 123123123123
+  2
+  3
+  4
+}
+
+bar = clazz.superclass == null || clazz.superclass.reflectee == Module || clazz.superclass.reflectee == Typed
+
+baz =
+new Listing {
+  1
+  2
+} |> mixin1 |> mixin2
+
+qux =
+  (baz) {
+    1
+    2
+  } {
+    3
+    4
+  }
+
+minus = superLoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongVariable - 100000

pkl-formatter/src/test/files/FormatterSnippetTests/input/expr-chain.pkl

@@ -0,0 +1,5 @@
+res = myList.map((it) -> it.partition).filter((it) -> someList.contains(it))
+
+res2 = myList.map(lambda1).filter(lambda2)
+
+res3 = myList.map((it) -> it.partition)

pkl-formatter/src/test/files/FormatterSnippetTests/input/expr-if.pkl

@@ -0,0 +1,7 @@
+foo =
+  if (someCondition) 10000
+  else
+    if (someOtherCondition) 20000
+    else
+      if (someAnotherCondition) 30000
+      else 4

pkl-formatter/src/test/files/FormatterSnippetTests/input/expr-let.pkl

@@ -0,0 +1,11 @@
+
+foo = let (vaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaariable = 10) 1 * 1
+
+bar = let (someVariable = new Listing {
+    1
+  }) 1 * 1
+
+baz =
+  let (someVariable = 10000000)
+    let (someOtherVariable = 2000000)
+      let (someAnotherVariable = 3000000) someVariable + someOtherVariable + someAnotherVariable

pkl-formatter/src/test/files/FormatterSnippetTests/input/imports.pkl

@@ -0,0 +1,19 @@
+// top level comment
+
+import "@foo/Foo.pkl" as foo
+import* "**.pkl"
+import "pkl:math"
+
+import "package://example.com/myPackage@1.0.0#/Qux.pkl"
+import* "file:///tmp/*.pkl"
+
+
+import "https://example.com/baz.pkl"
+import "module2.pkl"
+import "pkl:reflect"
+import "..."
+import* "@foo/**.pkl"
+import "@bar/Bar.pkl"
+import "Module12.pkl"
+import "module11.pkl"
+import "module1.pkl"

pkl-formatter/src/test/files/FormatterSnippetTests/input/indentation.pkl

@@ -0,0 +1,51 @@
+foo = new {
+bar = 1
+}
+
+class Foo {
+    baz: Int
+}
+
+bar =
+  new Listing {
+    1
+    2
+  }
+
+baz =
+(foo) {
+  2
+  3
+}
+
+qux =
+  (x, y) -> new Listing {
+    x
+    y
+  }
+
+forGen = new Listing {
+  for (someVar in new Listing {
+    1
+    2
+  }) {
+    [someVar] = someVar
+  }
+}
+
+objParams: Listing<Int> =
+  new {
+  default {
+    key -> key + 1
+  }
+}
+
+objParams2: Listing<Int> = new {
+  default { someVeryLongParameter1, someVeryLongParameter2, someVeryLongParameter3, someVeryLongParameter4 ->
+    1
+  }
+}
+
+parenType: (ReaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongType(reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalylongConstraint))
+
+functionType: (ReaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongType,ReaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongType2) -> String

pkl-formatter/src/test/files/FormatterSnippetTests/input/line-breaks.pkl

@@ -0,0 +1,64 @@
+module
+foo.bar.baz
+amends
+"bar.pkl"
+
+import
+"@foo/Foo.pkl"
+as foo
+
+local
+open
+class Bar {}
+
+const
+local
+baz = 10
+
+local
+function
+fun(x) =
+  x
+
+const local prooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooperty: String = "foo"
+
+local function function2(parameter1: Parameter1Type, parameter2: Parameter2Type, parameter3: Parameter3Type, parameter4: Parameter4Type): String = ""
+
+local const function function3(parameter1: String|Int, parameter2: String|Int): Mapping<String|Int, String> =
+  new {}
+
+prop = function2(loooooooooooooooooogParameter1, loooooooooooooooooogParameter2, loooooooooooooooooogParameter3, loooooooooooooooooogParameter4)
+
+prop2: String
+  |Int
+  |Boolean
+
+funcParam = fun(
+  (x, y) -> new Listing {
+  x
+  y
+})
+
+funcParam2 = aFun(foo, 10 * 10, anotherVariable, if (true) 100000 else 200000, (param1, param2) -> param1 * param2)
+
+funcParam3 = aFun(foo, 10 * 10, anotherVariable, 200000, (param1, param2) -> param1 * param2)
+
+funcParam4 = aFun(foo, 10 * 10, anotherVariable, if (true) 100000 else 200000, new Listing {
+  1
+  2
+})
+
+open local class SomeReallyInterestingClassName<in SomeInParameter, out SomeOutParameter> extends AnotherInterestingClassName {
+  foo: Int
+}
+
+local function resourceMapping(type): Mapping<String, unknown> =
+  new Mapping { default = (key) -> (type) { metadata { name = key } } }
+
+local const function biiiiiiiiiiiiiiiiiiiiiiiiigFunction(param1: String, param2: String(!isBlank)): Boolean
+
+local const function someFunction(param1: String, param2: String(!isBlank)): Boolean
+
+local function render(currentIndent: String) =
+  "\(currentIndent)@\(identifier.render(currentIndent))" +
+    if (body == null) "" else " " + body.render(currentIndent)

pkl-formatter/src/test/files/FormatterSnippetTests/input/line-breaks2.pkl

@@ -0,0 +1,20 @@
+module reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaly.loooooooooooooooooooooooooooooooog.naaaaaaaaaaaaaaaaaaaaaaaaaame
+extends "reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongModule.pkl"
+
+import "reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongModule.pkl" as foo
+
+local open class LoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongName {}
+
+local open class ReaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongName {}
+
+const hidden loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooogName = 99
+
+const hidden reallyLoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooogName = 99
+
+const local function looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooogName(x: Int, y) = x + y
+
+typealias Foo = LooooooooooooooooooooooooongTypeName|AnotherLooooooooooooooooooooooooongTypeName|OtherLooooooooooooooooooooooooongTypeName
+
+bar: Boolean|Mapping<LooooooooooooooooooooooooooooongTypeName, AnotherLooooooooooooooooooooooooooooongTypeName>(loooooooooooooooooooogConstraint)
+
+hidden foobar: LongType(someVeryyyyyyyloooong, requirements.might.be.even_loooooooooooooooooooooooooooooooooooooooooooooooooooooooooonger)

pkl-formatter/src/test/files/FormatterSnippetTests/input/line-width.pkl

@@ -0,0 +1,18 @@
+module reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaly.loooooooooooooooooooooooooooooooog.naaaaaaaaaaaaaaaaaaaaaaaaaaaaame
+extends "reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongModule.pkl"
+
+local reallyLongVariableName = true
+local anotherReallyLongName = 1
+local evenLongerVariableName = 2
+
+/// this property has a reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaly long doc comment
+property = if (reallyLongVariableName) anotherReallyLongName else evenLongerVariableName + anotherReallyLongName
+
+longString = "reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaly long string"
+
+shortProperty = 1
+
+reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongVariableName = 10
+
+reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongVariableName2 =
+  if (reallyLongVariableName) anotherReallyLongName else evenLongerVariableName + anotherReallyLongName

pkl-formatter/src/test/files/FormatterSnippetTests/input/map-function.pkl

@@ -0,0 +1,4 @@
+
+foo = Map(1000, "some random string", 20000, "another random string", 30000, "yet another random string")
+
+incorrect = Map("This has", 1000000, "an incorrect number", 2000000, "of parameters", 30000000, "passed to Map")

pkl-formatter/src/test/files/FormatterSnippetTests/input/modifiers.pkl

@@ -0,0 +1,3 @@
+hidden const foo = 1
+
+open local class Foo {}

pkl-formatter/src/test/files/FormatterSnippetTests/input/module-definitions.pkl

@@ -0,0 +1,13 @@
+// comment
+// one
+
+
+/// doc comment
+
+open
+module
+foo
+  .bar
+
+amends
+"baz.pkl"

pkl-formatter/src/test/files/FormatterSnippetTests/input/multi-line-strings.pkl

@@ -0,0 +1,29 @@
+foo = """
+  asd \(new {
+  bar = 1
+}) asd
+  """
+
+bar = """
+      line 1
+        line 2
+          line3
+      """
+
+baz = """
+\n
+\(bar)
+line
+\u{123}
+"""
+
+// remove unneeded spaces
+qux = """
+  foo
+  
+  bar
+  
+  baz
+    
+  \(foo)
+  """

pkl-formatter/src/test/files/FormatterSnippetTests/input/object-members.pkl

@@ -0,0 +1,22 @@
+foo: Listing<Int> = new {1 2   3; 4;5 6  7}
+
+bar: Listing<Int> = new { 1 2
+  3
+  4
+}
+
+lineIsTooBig: Listing<Int> = new { 999999; 1000000; 1000001; 1000002; 1000003; 1000004; 1000005; 1000006; 1000007; 1000008; 1000009 }
+
+lineIsTooBig2 { 999999; 1000000; 1000001; 1000002; 1000003; 1000004; 1000005; 1000006; 1000007; 1000008; 1000009; 1000010 }
+
+baz = new Dynamic {
+  1 2
+  3 4
+
+  ["foo"] = 3; bar = 30
+
+
+  baz = true
+}
+
+qux = new Dynamic {1 2 3 prop="prop"; [0]=9}

pkl-formatter/src/test/files/FormatterSnippetTests/input/prefixes.pkl

@@ -0,0 +1,12 @@
+
+/// Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong doc comment
+@Annotation { looooooooooooooooooooooooooooooooooooooooooooooooooongVariableName = 10 }
+typealias Foo = String
+
+/// Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong doc comment
+@Annotation { looooooooooooooooooooooooooooooooooooooooooooooooooongVariableName = 10 }
+foo = "should fit in a single line"
+
+/// Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong doc comment
+@Annotation { looooooooooooooooooooooooooooooooooooooooooooooooooongVariableName = 10 }
+function bar(x): String = "result: \(x)"

pkl-formatter/src/test/files/FormatterSnippetTests/input/spaces.pkl

@@ -0,0 +1,23 @@
+import"foo.pkl"
+
+bar=new  Listing < Int > ( !isEmpty ){1;2}//a bar
+
+typealias Typealias=(String,Int)->Boolean
+
+///a baz
+///returns its parameter
+baz = (x,y,z)->x+y+z
+
+function fun ( x:Int ? ,b  :Boolean )= if(b)/***return x**/x else x+bar [0 ]
+
+prop = trace (1) + super . foo + module .foo
+
+prop2 {
+  for(x in List(1)) {
+    when(x == 1){
+      x
+    }
+  }
+}
+
+choices: "foo" | * "bar" | String

pkl-formatter/src/test/files/FormatterSnippetTests/input/type-aliases.pkl

@@ -0,0 +1,6 @@
+typealias
+  Foo
+  =
+  String
+
+typealias VeryLoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongTypeAlias = String(!isEmpty)

pkl-formatter/src/test/files/FormatterSnippetTests/input/when.pkl

@@ -0,0 +1,9 @@
+foo {
+  when  (true)
+  {
+  bar = 1
+  }
+  else {
+    bar = 2
+  }
+}

pkl-formatter/src/test/files/FormatterSnippetTests/output/class-bodies.pkl

@@ -0,0 +1,11 @@
+class Foo {}
+
+class Bar {
+  qux = 1
+}
+
+class Baz {
+  prop = 0
+
+  prop2 = 1
+}

pkl-formatter/src/test/files/FormatterSnippetTests/output/comma-termination.pkl

@@ -0,0 +1,35 @@
+function fun(a, b, c, d) = a
+
+noTrailingCommas = fun(1, 2, 3, 4)
+
+trailingCommas =
+  fun(
+    "loooooooooooooooooooongString",
+    "loooooooooooooooongString",
+    "looooooooooooooooongString",
+    "notTooLong",
+  )
+
+noTrailingCommaObjParams {
+    fooooooooooooooooooooooooooooooooo,
+    baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaar,
+    baaaaaaaaaaaaaaaaaaaaaz ->
+  1 + 1
+}
+
+trailingCommaInLambdas = (
+  fooooooooooooooooooooooooooooooooo,
+  baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaar,
+  baaaaaaaaaaaaaaaaaaaaaz,
+) -> 1
+
+trailingCommaInConstraints: String(
+  isSomethingSomethingSomething,
+  isSomethingElse,
+  isSomethingSomethingSomethingElse,
+)
+
+trailingCommaInTypeParameters: Mapping<
+  SomethingSomethingSomethingSomething,
+  SomethingSomething | SomethingElse,
+>

pkl-formatter/src/test/files/FormatterSnippetTests/output/comment-interleaved.pkl

@@ -0,0 +1,34 @@
+module comment.interleaved
+
+local test: Int | String =
+  if (true)
+    1 // It's the same as "100%"
+  else
+    "8%"
+
+foo: ( // some comment
+  *String(
+    // if dtstart is defined and a datetime, until must also be a datetime if defined
+    true,
+  )
+    | Int
+  // trailing comment
+)?
+
+foo2: ( // some comment
+  Int, // other comment
+  String,
+) ->
+  Int
+
+bar =
+  ( // some comment
+    10 + 10
+    // another comment
+  )
+
+bar2 = ( // some comment
+  foo,
+  bar
+  // another comment
+) -> foo + bar

pkl-formatter/src/test/files/FormatterSnippetTests/output/dangling-doc-comment.pkl

@@ -0,0 +1,8 @@
+module dangling
+
+/// Doc comment.
+///
+/// for this field
+// sepearted by a stray comment
+/// but continues here.
+some: String

pkl-formatter/src/test/files/FormatterSnippetTests/output/doc-comments.pkl

@@ -0,0 +1,13 @@
+/// / line 1
+/// // line 2
+foo = 1
+
+/// line 1
+///
+///
+/// line 2
+bar = 1
+
+/// line 1
+/// line 2
+baz = 1

pkl-formatter/src/test/files/FormatterSnippetTests/output/expr-binary.pkl

@@ -0,0 +1,34 @@
+foo {
+  123123123123
+    + 123123123123 * 123123123123 -
+    123123123123 / 123123123123
+    + 123123123123 ** 123123123123
+  2
+  3
+  4
+}
+
+bar =
+  clazz.superclass == null
+    || clazz.superclass.reflectee == Module
+    || clazz.superclass.reflectee == Typed
+
+baz =
+  new Listing {
+    1
+    2
+  }
+    |> mixin1
+    |> mixin2
+
+qux = (baz) {
+  1
+  2
+} {
+  3
+  4
+}
+
+minus =
+  superLoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongVariable -
+    100000

pkl-formatter/src/test/files/FormatterSnippetTests/output/expr-chain.pkl

@@ -0,0 +1,8 @@
+res =
+  myList
+    .map((it) -> it.partition)
+    .filter((it) -> someList.contains(it))
+
+res2 = myList.map(lambda1).filter(lambda2)
+
+res3 = myList.map((it) -> it.partition)

pkl-formatter/src/test/files/FormatterSnippetTests/output/expr-if.pkl

@@ -0,0 +1,9 @@
+foo =
+  if (someCondition)
+    10000
+  else if (someOtherCondition)
+    20000
+  else if (someAnotherCondition)
+    30000
+  else
+    4

pkl-formatter/src/test/files/FormatterSnippetTests/output/expr-let.pkl

@@ -0,0 +1,18 @@
+foo =
+  let (vaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaariable =
+      10
+  )
+    1 * 1
+
+bar =
+  let (someVariable = new Listing {
+      1
+    }
+  )
+    1 * 1
+
+baz =
+  let (someVariable = 10000000)
+  let (someOtherVariable = 2000000)
+  let (someAnotherVariable = 3000000)
+    someVariable + someOtherVariable + someAnotherVariable

pkl-formatter/src/test/files/FormatterSnippetTests/output/imports.pkl

@@ -0,0 +1,21 @@
+// top level comment
+
+import "https://example.com/baz.pkl"
+import "package://example.com/myPackage@1.0.0#/Qux.pkl"
+import "pkl:math"
+import "pkl:reflect"
+
+import "@bar/Bar.pkl"
+import "@foo/Foo.pkl" as foo
+
+import "..."
+import "module1.pkl"
+import "module2.pkl"
+import "module11.pkl"
+import "Module12.pkl"
+
+import* "file:///tmp/*.pkl"
+
+import* "@foo/**.pkl"
+
+import* "**.pkl"

pkl-formatter/src/test/files/FormatterSnippetTests/output/indentation.pkl

@@ -0,0 +1,61 @@
+foo = new {
+  bar = 1
+}
+
+class Foo {
+  baz: Int
+}
+
+bar = new Listing {
+  1
+  2
+}
+
+baz = (foo) {
+  2
+  3
+}
+
+qux = (x, y) -> new Listing {
+  x
+  y
+}
+
+forGen = new Listing {
+  for (
+    someVar in new Listing {
+      1
+      2
+    }
+  ) {
+    [someVar] = someVar
+  }
+}
+
+objParams: Listing<Int> = new {
+  default { key ->
+    key + 1
+  }
+}
+
+objParams2: Listing<Int> = new {
+  default {
+      someVeryLongParameter1,
+      someVeryLongParameter2,
+      someVeryLongParameter3,
+      someVeryLongParameter4 ->
+    1
+  }
+}
+
+parenType: (
+  ReaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongType(
+    reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalylongConstraint,
+  )
+)
+
+functionType: (
+  ReaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongType,
+  ReaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongType2,
+) ->
+  String

pkl-formatter/src/test/files/FormatterSnippetTests/output/line-breaks.pkl

@@ -0,0 +1,75 @@
+module foo.bar.baz
+
+amends "bar.pkl"
+
+import "@foo/Foo.pkl" as foo
+
+open local class Bar {}
+
+local const baz = 10
+
+local function fun(x) = x
+
+local const prooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooperty: String =
+  "foo"
+
+local function function2(
+  parameter1: Parameter1Type,
+  parameter2: Parameter2Type,
+  parameter3: Parameter3Type,
+  parameter4: Parameter4Type,
+): String = ""
+
+local const function function3(
+  parameter1: String | Int,
+  parameter2: String | Int,
+): Mapping<String | Int, String> = new {}
+
+prop =
+  function2(
+    loooooooooooooooooogParameter1,
+    loooooooooooooooooogParameter2,
+    loooooooooooooooooogParameter3,
+    loooooooooooooooooogParameter4,
+  )
+
+prop2: String | Int | Boolean
+
+funcParam =
+  fun((x, y) -> new Listing {
+    x
+    y
+  })
+
+funcParam2 =
+  aFun(foo, 10 * 10, anotherVariable, if (true) 100000 else 200000, (param1, param2) ->
+    param1 * param2
+  )
+
+funcParam3 = aFun(foo, 10 * 10, anotherVariable, 200000, (param1, param2) -> param1 * param2)
+
+funcParam4 =
+  aFun(foo, 10 * 10, anotherVariable, if (true) 100000 else 200000, new Listing {
+    1
+    2
+  })
+
+open local class SomeReallyInterestingClassName<in SomeInParameter, out SomeOutParameter>
+  extends AnotherInterestingClassName {
+  foo: Int
+}
+
+local function resourceMapping(type): Mapping<String, unknown> = new Mapping {
+  default = (key) -> (type) { metadata { name = key } }
+}
+
+local const function biiiiiiiiiiiiiiiiiiiiiiiiigFunction(
+  param1: String,
+  param2: String(!isBlank),
+): Boolean
+
+local const function someFunction(param1: String, param2: String(!isBlank)): Boolean
+
+local function render(currentIndent: String) =
+  "\(currentIndent)@\(identifier.render(currentIndent))"
+    + if (body == null) "" else " " + body.render(currentIndent)

pkl-formatter/src/test/files/FormatterSnippetTests/output/line-breaks2.pkl

@@ -0,0 +1,42 @@
+module
+  reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaly
+    .loooooooooooooooooooooooooooooooog
+    .naaaaaaaaaaaaaaaaaaaaaaaaaame
+
+extends
+  "reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongModule.pkl"
+
+import
+  "reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongModule.pkl"
+  as foo
+
+open local class LoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongName {}
+
+open local class ReaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongName {}
+
+hidden const loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooogName =
+  99
+
+hidden const reallyLoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooogName =
+  99
+
+local const function looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooogName(
+  x: Int,
+  y,
+) = x + y
+
+typealias Foo =
+  LooooooooooooooooooooooooongTypeName
+    | AnotherLooooooooooooooooooooooooongTypeName
+    | OtherLooooooooooooooooooooooooongTypeName
+
+bar: Boolean
+  | Mapping<
+    LooooooooooooooooooooooooooooongTypeName,
+    AnotherLooooooooooooooooooooooooooooongTypeName,
+  >(loooooooooooooooooooogConstraint)
+
+hidden foobar: LongType(
+  someVeryyyyyyyloooong,
+  requirements.might.be.even_loooooooooooooooooooooooooooooooooooooooooooooooooooooooooonger,
+)

pkl-formatter/src/test/files/FormatterSnippetTests/output/line-width.pkl

@@ -0,0 +1,32 @@
+module
+  reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaly
+    .loooooooooooooooooooooooooooooooog
+    .naaaaaaaaaaaaaaaaaaaaaaaaaaaaame
+
+extends
+  "reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongModule.pkl"
+
+local reallyLongVariableName = true
+local anotherReallyLongName = 1
+local evenLongerVariableName = 2
+
+/// this property has a reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaly long doc comment
+property =
+  if (reallyLongVariableName)
+    anotherReallyLongName
+  else
+    evenLongerVariableName + anotherReallyLongName
+
+longString =
+  "reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaly long string"
+
+shortProperty = 1
+
+reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongVariableName =
+  10
+
+reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaalyLongVariableName2 =
+  if (reallyLongVariableName)
+    anotherReallyLongName
+  else
+    evenLongerVariableName + anotherReallyLongName

pkl-formatter/src/test/files/FormatterSnippetTests/output/map-function.pkl

@@ -0,0 +1,14 @@
+foo =
+  Map(
+    1000, "some random string",
+    20000, "another random string",
+    30000, "yet another random string",
+  )
+
+incorrect =
+  Map(
+    "This has", 1000000,
+    "an incorrect number", 2000000,
+    "of parameters", 30000000,
+    "passed to Map",
+  )

pkl-formatter/src/test/files/FormatterSnippetTests/output/modifiers.pkl

@@ -0,0 +1,3 @@
+hidden const foo = 1
+
+open local class Foo {}

pkl-formatter/src/test/files/FormatterSnippetTests/output/module-definitions.pkl

@@ -0,0 +1,7 @@
+// comment
+// one
+
+/// doc comment
+open module foo.bar
+
+amends "baz.pkl"

pkl-formatter/src/test/files/FormatterSnippetTests/output/multi-line-strings.pkl

@@ -0,0 +1,33 @@
+foo =
+  """
+  asd \(new {
+    bar = 1
+  }) asd
+  """
+
+bar =
+  """
+  line 1
+    line 2
+      line3
+  """
+
+baz =
+  """
+  \n
+  \(bar)
+  line
+  \u{123}
+  """
+
+// remove unneeded spaces
+qux =
+  """
+  foo
+
+  bar
+
+  baz
+    
+  \(foo)
+  """

pkl-formatter/src/test/files/FormatterSnippetTests/output/object-members.pkl

@@ -0,0 +1,51 @@
+foo: Listing<Int> = new { 1; 2; 3; 4; 5; 6; 7 }
+
+bar: Listing<Int> = new {
+  1
+  2
+  3
+  4
+}
+
+lineIsTooBig: Listing<Int> = new {
+  999999
+  1000000
+  1000001
+  1000002
+  1000003
+  1000004
+  1000005
+  1000006
+  1000007
+  1000008
+  1000009
+}
+
+lineIsTooBig2 {
+  999999
+  1000000
+  1000001
+  1000002
+  1000003
+  1000004
+  1000005
+  1000006
+  1000007
+  1000008
+  1000009
+  1000010
+}
+
+baz = new Dynamic {
+  1
+  2
+  3
+  4
+
+  ["foo"] = 3
+  bar = 30
+
+  baz = true
+}
+
+qux = new Dynamic { 1; 2; 3; prop = "prop"; [0] = 9 }

pkl-formatter/src/test/files/FormatterSnippetTests/output/prefixes.pkl

@@ -0,0 +1,11 @@
+/// Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong doc comment
+@Annotation { looooooooooooooooooooooooooooooooooooooooooooooooooongVariableName = 10 }
+typealias Foo = String
+
+/// Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong doc comment
+@Annotation { looooooooooooooooooooooooooooooooooooooooooooooooooongVariableName = 10 }
+foo = "should fit in a single line"
+
+/// Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong doc comment
+@Annotation { looooooooooooooooooooooooooooooooooooooooooooooooooongVariableName = 10 }
+function bar(x): String = "result: \(x)"

pkl-formatter/src/test/files/FormatterSnippetTests/output/spaces.pkl

@@ -0,0 +1,23 @@
+import "foo.pkl"
+
+bar = new Listing<Int>(!isEmpty) { 1; 2 } //a bar
+
+typealias Typealias = (String, Int) -> Boolean
+
+/// a baz
+/// returns its parameter
+baz = (x, y, z) -> x + y + z
+
+function fun(x: Int?, b: Boolean) = if (b) /***return x**/ x else x + bar[0]
+
+prop = trace(1) + super.foo + module.foo
+
+prop2 {
+  for (x in List(1)) {
+    when (x == 1) {
+      x
+    }
+  }
+}
+
+choices: "foo" | *"bar" | String

pkl-formatter/src/test/files/FormatterSnippetTests/output/type-aliases.pkl

@@ -0,0 +1,4 @@
+typealias Foo = String
+
+typealias VeryLoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongTypeAlias =
+  String(!isEmpty)

pkl-formatter/src/test/files/FormatterSnippetTests/output/when.pkl

@@ -0,0 +1,7 @@
+foo {
+  when (true) {
+    bar = 1
+  } else {
+    bar = 2
+  }
+}

pkl-formatter/src/test/kotlin/org/pkl/formatter/FormatterSnippetTests.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.formatter
+
+import org.junit.platform.commons.annotation.Testable
+
+@Testable class FormatterSnippetTests

pkl-formatter/src/test/kotlin/org/pkl/formatter/FormatterSnippetTestsEngine.kt

@@ -0,0 +1,73 @@
+/*
+ * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.formatter
+
+import java.nio.file.Path
+import kotlin.io.path.isRegularFile
+import kotlin.reflect.KClass
+import org.pkl.commons.test.InputOutputTestEngine
+import org.pkl.parser.ParserError
+
+abstract class AbstractFormatterSnippetTestsEngine : InputOutputTestEngine() {
+
+  private val snippetsDir: Path =
+    rootProjectDir.resolve("pkl-formatter/src/test/files/FormatterSnippetTests")
+
+  private val expectedOutputDir: Path = snippetsDir.resolve("output")
+
+  /** Convenience for development; this selects which snippet test(s) to run. */
+  // language=regexp
+  internal val selection: String = ""
+
+  override val includedTests: List<Regex> = listOf(Regex(".*$selection\\.pkl"))
+
+  override val inputDir: Path = snippetsDir.resolve("input")
+
+  override val isInputFile: (Path) -> Boolean = { it.isRegularFile() }
+
+  override fun expectedOutputFileFor(inputFile: Path): Path {
+    val relativePath = relativize(inputFile, inputDir).toString()
+    return expectedOutputDir.resolve(relativePath)
+  }
+
+  companion object {
+    private fun relativize(path: Path, base: Path): Path {
+      if (System.getProperty("os.name").contains("Windows")) {
+        if (path.isAbsolute && base.isAbsolute && (path.root != base.root)) {
+          return path
+        }
+      }
+      return base.relativize(path)
+    }
+  }
+}
+
+class FormatterSnippetTestsEngine : AbstractFormatterSnippetTestsEngine() {
+  override val testClass: KClass<*> = FormatterSnippetTests::class
+
+  override fun generateOutputFor(inputFile: Path): Pair<Boolean, String> {
+    val formatter = Formatter()
+    val (success, output) =
+      try {
+        val res = formatter.format(inputFile)
+        true to res
+      } catch (_: ParserError) {
+        false to ""
+      }
+
+    return success to output
+  }
+}

pkl-formatter/src/test/kotlin/org/pkl/formatter/FormatterTest.kt

@@ -0,0 +1,79 @@
+/*
+ * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.formatter
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.pkl.parser.GenericParserError
+
+class FormatterTest {
+
+  @Test
+  fun `multiline string - wrong start quote`() {
+    val ex =
+      assertThrows<GenericParserError> {
+        format(
+          """
+        foo = ""${'"'}line1
+          line 2
+          ""${'"'}
+      """
+        )
+      }
+
+    assertThat(ex.message).contains("The content of a multi-line string must begin on a new line")
+  }
+
+  @Test
+  fun `multiline string - wrong end quote`() {
+    val ex =
+      assertThrows<GenericParserError> {
+        format(
+          """
+        foo = ""${'"'}
+          line1
+          line 2""${'"'}
+      """
+        )
+      }
+
+    assertThat(ex.message)
+      .contains("The closing delimiter of a multi-line string must begin on a new line")
+  }
+
+  @Test
+  fun `multiline string - wrong indentation`() {
+    val ex =
+      assertThrows<GenericParserError> {
+        format(
+          """
+        foo = ""${'"'}
+          line1
+        line 2
+          ""${'"'}
+      """
+        )
+      }
+
+    assertThat(ex.message)
+      .contains("Line must match or exceed indentation of the String's last line.")
+  }
+
+  private fun format(code: String): String {
+    return Formatter().format(code.trimIndent())
+  }
+}

pkl-formatter/src/test/resources/META-INF/services/org.junit.platform.engine.TestEngine

@@ -0,0 +1 @@
+org.pkl.formatter.FormatterSnippetTestsEngine