Allow renaming Java/Kotlin classes/packages during code generation (#499)

Adds a `rename` field to the Java/Kotlin code generators that allows renaming packages and classes during codegen.

* Add `--rename` flag to CLIs
* Add `rename` property to Gradle API

pkl-commons/src/main/kotlin/org/pkl/commons/NameMapper.kt

@@ -0,0 +1,73 @@
+/**
+ * Copyright © 2024 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.commons
+
+/**
+ * A helper class for translating names of Pkl modules to different names of classes and/or objects
+ * in the target language of a code generation execution.
+ *
+ * The `mapping` parameter is expected to contain valid prefixes of Pkl module names, with an
+ * optional dot at the end, and values should be valid class names in the language for which code
+ * generation is performed.
+ *
+ * If the rename patterns do not explicitly rename the class, the class name is capitalized.
+ *
+ * When computing the appropriate target name, the longest matching prefix is used.
+ *
+ * Prefix replacements are literal, and therefore dots are important. When renaming packages, in
+ * most cases, you must ensure that you have an ending dot on both sides of a mapping (except for
+ * the empty mapping, if you use it), otherwise you may get unexpected results:
+ * ```kotlin
+ * val mapper = NameMapper(
+ *   mapOf(
+ *     "com.foo." to "x", // Dot on the left only
+ *     "org.bar" to "y.", // Dot on the right only
+ *     "net.baz" to "z" // No dots
+ *   )
+ * )
+ *
+ * assertThat(mapper.map("com.foo.bar")).isEqualTo("" to "xbar") // Target prefix merged into the suffix
+ * assertThat(mapper.map("org.bar.baz")).isEqualTo("y." to "Baz") // Double dot, invalid package name
+ * assertThat(mapper.map("net.baz.qux")).isEqualTo("z" to "Qux") // Looks okay, but...
+ * assertThat(mapper.map("net.bazqux")).isEqualTo("" to "zqux") // ...may cut the package name in the middle.
+ * ```
+ */
+class NameMapper(mapping: Map<String, String>) {
+  private val sortedMapping = mapping.toList().sortedBy { -it.first.length }
+
+  private fun doMap(sourceName: String): Pair<String, Boolean> {
+    for ((sourcePrefix, targetPrefix) in sortedMapping) {
+      if (sourceName.startsWith(sourcePrefix)) {
+        val rest = sourceName.substring(sourcePrefix.length)
+        val mapped = targetPrefix + rest
+        val wasClassRenamed =
+          !targetPrefix.endsWith('.') && (sourcePrefix.length - 1) >= sourceName.lastIndexOf('.')
+        return mapped to wasClassRenamed
+      }
+    }
+    return sourceName to false
+  }
+
+  fun map(sourceName: String): Pair<String, String> {
+    val (mappedName, wasClassRenamed) = doMap(sourceName)
+    val packageName = mappedName.substringBeforeLast(".", "")
+    val mappedClassName = mappedName.substringAfterLast(".")
+    val className =
+      if (wasClassRenamed) mappedClassName
+      else mappedClassName.replaceFirstChar { it.titlecaseChar() }
+    return packageName to className
+  }
+}

pkl-commons/src/test/kotlin/org/pkl/commons/NameMapperTest.kt

@@ -0,0 +1,59 @@
+/**
+ * Copyright © 2024 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.commons
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+
+class NameMapperTest {
+  @Test
+  fun `empty prefixes everything`() {
+    val mapper = NameMapper(mapOf("" to "bar."))
+    assertThat(mapper.map("foo.bar.Baz")).isEqualTo("bar.foo.bar" to "Baz")
+    assertThat(mapper.map("Baz")).isEqualTo("bar" to "Baz")
+  }
+
+  @Test
+  fun `longest prefix wins`() {
+    val mapper = NameMapper(mapOf("bar." to "com.bar.", "bar.baz." to "foo.bar."))
+    assertThat(mapper.map("bar.baz.Buzzy")).isEqualTo("foo.bar" to "Buzzy")
+  }
+
+  @Test
+  fun `implicit uppercase classname`() {
+    val mapper = NameMapper(mapOf("foo." to "bar."))
+    assertThat(mapper.map("foo.bar.baz")).isEqualTo("bar.bar" to "Baz")
+    assertThat(mapper.map("foo.bar")).isEqualTo("bar" to "Bar")
+    assertThat(mapper.map("baz")).isEqualTo("" to "Baz")
+    assertThat(mapper.map("baz")).isEqualTo("" to "Baz")
+  }
+
+  @Test
+  fun `no implicit uppercased classname if explicitly renamed`() {
+    val mapper =
+      NameMapper(
+        mapOf(
+          "foo.bar" to "bar.bar",
+          "foo.c" to "foo.z",
+          "com.foo." to "x",
+        )
+      )
+    assertThat(mapper.map("foo.bar")).isEqualTo("bar" to "bar")
+    assertThat(mapper.map("foo.bar")).isEqualTo("bar" to "bar")
+    assertThat(mapper.map("foo.cow")).isEqualTo("foo" to "zow")
+    assertThat(mapper.map("com.foo.bar")).isEqualTo("" to "xbar")
+  }
+}