= Pkl 0.30 Release Notes
:version: 0.30
:version-minor: 0.30.0
:release-date: November 3rd, 2025

:yaml-binary-scalar: https://yaml.org/type/binary.html

include::ROOT:partial$component-attributes.adoc[]

Pkl {version} was released on {release-date}. +
[.small]#The latest bugfix release is {version-minor}. (xref:changelog.adoc[All Versions])#

This release introduces a code formatter, and an in-language API for producing `pkl-binary` output.

The next release (0.31) is scheduled for February 2026.
To see what's coming in the future, follow the {uri-pkl-roadmap}[Pkl Roadmap].

Please send feedback and questions to https://github.com/apple/pkl/discussions[GitHub Discussions], or submit an issue on https://github.com/apple/pkl/issues/new[GitHub]. +

[small]#Pkl is hosted on https://github.com/apple/pkl[GitHub].
To get started, follow xref:pkl-cli:index.adoc#installation[Installation].#

== Highlights [small]#💖#

[[formatter]]
=== Formatter

Pkl now has a formatter (https://github.com/apple/pkl/pull/1107[#1107], https://github.com/apple/pkl/pull/1208[#1208], https://github.com/apple/pkl/pull/1211[#1211], https://github.com/apple/pkl/pull/1215[#1215], https://github.com/apple/pkl/pull/1217[#1217], https://github.com/apple/pkl/pull/1235[#1235], https://github.com/apple/pkl/pull/1246[#1246], https://github.com/apple/pkl/pull/1247[#1247], https://github.com/apple/pkl/pull/1252[#1252], https://github.com/apple/pkl/pull/1256[#1256], https://github.com/apple/pkl/pull/1259[#1259], https://github.com/apple/pkl/pull/1260[#1260], https://github.com/apple/pkl/pull/1263[#1263], https://github.com/apple/pkl/pull/1265[#1265], https://github.com/apple/pkl/pull/1266[#1266], https://github.com/apple/pkl/pull/1267[#1267], https://github.com/apple/pkl/pull/1268[#1268], https://github.com/apple/pkl/pull/1270[#1270], https://github.com/apple/pkl/pull/1271[#1271], https://github.com/apple/pkl/pull/1272[#1272], https://github.com/apple/pkl/pull/1273[#1273], https://github.com/apple/pkl/pull/1274[#1274], https://github.com/apple/pkl/pull/1280[#1280], https://github.com/apple/pkl/pull/1283[#1283], https://github.com/apple/pkl/pull/1289[#1289], https://github.com/apple/pkl/pull/1290[#1290])!

Pkl's formatter is _canonical_, which means that it has a single set of formatting rules, with (almost) no configuration options.
The goal is to eliminate the possibility of formatting debates, which can lead to churn and bike-shedding.

The formatter is available both as a CLI subcommand and as a Java API.

To learn more about this feature, consult https://github.com/apple/pkl-evolution/blob/main/spices/SPICE-0014-canonical-formatter.adoc[SPICE-0014].

==== Using the CLI

The Pkl formatter is available under the `pkl format` subcommand. By default, the command will concatenate and write all formatted content to standard out.

To simply check for formatting violations, getting formatted output on stdout is likely too verbose.
The `--silent` flag can be used to omit any output, and the <<formatting-exit-codes,exit code>> can be used to determine
if there are formatting violations.

[source,shell]
----
pkl format --silent . || echo "Formatting violations were found!"
----

Alternatively, the `--names` flag will print out the names of any files that have formatting violations.

[source,shell]
----
pkl format --diff-name-only .
----

To apply formatting, use the `--write` (`-w`) flag.
This also implies the `--diff-name-only` flag.

[source,shell]
----
pkl format -w .
----

[[formatting-exit-codes]]
==== Exit codes

The formatter will exit with the following codes:

|===
|Code |Description

|0
|No formatting violations were found.

|1
|Non-formatting errors occurred.

|11
|Formatting violations were found.
|===

==== Grammar version

The formatter can be configured with a _grammar version_, which maps to a Pkl version range.

|===
|Grammar version |Pkl versions

|1
|0.25 - 0.29

|2
|0.30+
|===

Grammar version 2 uses the newly introduced <<trailing-commas,trailing commas>> feature, and therefore is not compatible with existing versions of Pkl.
To ensure compatibility, use the `--grammar-version 1` CLI flag.

[[binary-renderer-parser]]
=== `pkl-binary` in-language Renderer

A new in-language API has been added to render values into xref:bindings-specification:binary-encoding.adoc[pkl-binary encoding] (https://github.com/apple/pkl/pull/1203[#1203],
https://github.com/apple/pkl/pull/1250[#1250], https://github.com/apple/pkl/pull/1275[#1275]).

It's sometimes useful to separate Pkl evaluation from data consumption when used as application or service configuration.
This is possible with the `pkl-binary` format, which is a lossless encoding of Pkl data.

In this approach, Pkl is first rendered into `pkl-binary` during build time, and then deserialized into classes and structs at startup time.
This means that the Pkl evaluator does not need to be shipped with the application, which improves code portability and eliminates runtime overhead.

However, currently, the API for getting this binary format is somewhat cumbersome.
Only the host languages have access to this API (for example, https://swiftpackageindex.com/apple/pkl-swift/0.6.0/documentation/pklswift/evaluator/evaluateexpressionraw(source:expression:)[`evaluateExpressionRaw`] in pkl-swift).
This means that one-off logic must be written to render this format in the host language.

In 0.30, this renderer is added as an in-language API, through the {uri-stdlib-pklbinaryModule}[`pkl:pklbinary`] standard library module.
Additionally, it is available through CLI flag `--format pkl-binary`.

For example:

// this is parsed instead of tested because DocSnippetTests only handles textual output (via ReplServer)
[source%parsed,pkl]
----
import "pkl:pklbinary"

output {
  renderer = new pklbinary.Renderer {}
}
----

To learn more about this feature, consult https://github.com/apple/pkl-evolution/blob/main/spices/SPICE-0021-binary-renderer-and-parser.adoc[SPICE-0021].

==== New renderer type: `BytesRenderer`

To enable the `pkl-binary` renderer feature, Pkl now supports renderers that produce `Bytes` output (https://github.com/apple/pkl/pull/1203[#1203]).

The existing `ValueRenderer` class now extends new class `BaseValueRenderer`, and a new `BytesRenderer` class is introduced.

Setting a module's output renderer to a `BytesRenderer` will control its resulting `output.bytes`.

This affects usage scenarios where a module's `output.bytes` is evaluated, for example, when using `pkl eval`.

==== Using `pkl-binary` data

Users of Pkl's language binding libraries can decode `pkl-binary` data into instances of code-generated types.

[tabs]
====
Java::
+
[source,java]
----
var encodedData = fetchEncodedData(); // some byte[] or InputStream
var config = Config.fromPklBinary(encodedData);
var appConfig = config.as(AppConfig.class);
----

Kotlin::
+
[source,kotlin]
----
val encodedData = fetchEncodedData() // some ByteArray or InputStream
val config = Config.fromPklBinary(encodedData, ValueMapper.preconfigured().forKotlin())
val appConfig = config.to<AppConfig>()
----

Go::
+
[source,go]
----
encodedData := fetchEncodedData() // some []byte
var appConfig AppConfig
if err := pkl.Unmarshal(encodedData, &appConfig); err != nil {
  // handle error
} 
----

Swift::
+
[source,swift]
----
let encodedData = fetchEncodedData() // some [UInt8]
let appConfig = try PklDecoder.decode(AppConfig.self, from: encodedData)
----
====

== Noteworthy [small]#🎶#

[[trailing-commas]]
=== Trailing Commas

Pkl's grammar has been updated to allow including a comma following the final item of comma-separated syntax elements (https://github.com/apple/pkl/pull/1137[#1137]).

These syntax elements are affected:

[source%tested,pkl]
----
function add(
  bar,
  baz, // <1>
) = bar + baz

foo = add(
  1,
  2, // <2>
)

typealias MyMapping<
  Key,
  Value, // <3>
> = Mapping<Key, Value>

bar: Mapping<
  String,
  Int, // <4>
>

baz: Mapping(
  !containsKey("forbidden key"),
  !containsKey("forbidden value"), // <5>
)

qux: (
  String,
  Int, // <6>
) -> Dynamic =
  (paramA, paramB) -> new Dynamic {
    quux = "\(paramA): \(paramB)"
  }

corge = (qux) {
  paramA,
  paramB, // <7>
  ->
  grault = paramA.length * paramB
}
----
<1> Function parameter lists in method definitions.
<2> Argument lists in method calls.
<3> Type parameter lists in generic type definitions.
<4> Type argument lists in type annotations and casts.
<5> Type constraint lists.
<6> Function type parameter lists in function type annotations.
<7> Object body parameter lists.

To learn more about this change, consult https://github.com/apple/pkl-evolution/blob/main/spices/SPICE-0019-trailing-commas.adoc[SPICE-0019].

=== Pretty-printed traces

A new evaluator option is added to enable pretty-printed traces (https://github.com/apple/pkl/pull/1100[#1100], https://github.com/apple/pkl/pull/1227[#1227], https://github.com/apple/pkl/pull/1230[#1230]).

Currently, the `trace()` operator will render values as a single line, and trims the output after 100 characters.
This can obscure information when debugging.

In 0.30, a new evaluator option is added to control how traces are emitted.
Two trace modes are introduced:

* `compact` - the current output mode (default).
* `pretty` - multiline, with no limit on output size.

For example, users of the CLI can specify `--trace-mode` as a flag.

[source,shell]
----
pkl eval --trace-mode pretty myModule.pkl  
----

Thanks to https://github.com/ssalevan[@ssalevan] for their contribution to this feature!

=== Better support for `Bytes` when rendering YAML

Previously, attempting to render a `Bytes` value using {uri-stdlib-YamlRenderer}[`YamlRenderer`] required the use of a link:{uri-stdlib-PcfRenderer-converters}[converter].
Now, Pkl can natively render YAML containing link:{yaml-binary-scalar}[binary scalars] (https://github.com/apple/pkl/pull/1276[#1276]).

[source,pkl%tested]
----
foo {
  bar = Bytes(1, 2, 3)
}

rendered = new YamlRenderer {}.renderValue(foo) // <1>
----
<1> Result: `bar: !!binary AQID`

Similarly, link:{uri-stdlib-YamlParser}[`yaml.Parser`] now parses binary YAML values as Pkl link:{uri-stdlib-Bytes}[`Bytes`] values (https://github.com/apple/pkl/pull/1277[#1277]).
This is a breaking change; previously these values were parsed as link:{uri-stdlib-String}[`String`] value containing the base64-encoded binary data.

[source,pkl%tested]
----
import "pkl:yaml"

yamlData = 
  """
  bytes: !!binary AQID
  """

parsed = new yaml.Parser {}.parse(yamlData).bytes // <1>
----
<1> Result: `Bytes(1, 2, 3)`

[[pkldoc-perf-improvements]]
=== `pkldoc` performance improvements

The `pkldoc` documentation generator has been overhauled (https://github.com/apple/pkl/pull/1169[#1169], https://github.com/apple/pkl/pull/1224[#1224], https://github.com/apple/pkl/pull/1241[#1241], https://github.com/apple/pkl/pull/1242[#1242]).

Currently, the `pkldoc` tool needs to consume much of an existing documentation website whenever generating new documentation.
This adds significant I/O overhead as a pkldoc documentation website grows.

The generator has been overhauled to minimize the amount of data needed to be read from the current site.

To read more about this change, consult https://github.com/apple/pkl-evolution/blob/main/spices/SPICE-0018-pkldoc-io-improvements.adoc[SPICE-0018].

[[pkldoc-migration]]
==== Migration

The new pkldoc website introduces breaking changes to the data model.
Because of this, existing sites must be migrated before using the `0.30` version of pkldoc.

To migrate, run the one-time command `pkldoc --migrate`.

=== Java API changes

==== New classes

New classes are introduced to the Java API.

* `org.pkl.core.PklBinaryDecoder`

==== New methods

New methods are introduced to the Java API.

* `org.pkl.core.Evaluator.evaluateExpressionPklBinary`
* `org.pkl.core.EvaluatorBuilder.setTraceMode`
* `org.pkl.core.EvaluatorBuilder.getTraceMode`
* `org.pkl.config.java.Config.fromPklBinary`

=== Standard Library changes

New modules, properties, methods, classes and typealiases have been added to the standard library (https://github.com/apple/pkl/pull/1106[#1106]).

==== Changes to `pkl:base`

Additions:

* New class: {uri-stdlib-BaseValueRenderer}[`BaseValueRenderer`]
* {uri-stdlib-ValueRenderer}[`ValueRenderer`] (now a subclass of {uri-stdlib-BaseValueRenderer}[`BaseValueRenderer`])
* {uri-stdlib-BytesRenderer}[`BytesRenderer`]
* {uri-stdlib-baseModule}/RenderDirective#bytes[`RenderDirective.bytes`]

==== Additions to `pkl:EvaluatorSettings`

* {uri-stdlib-evaluatorSettingsModule}#traceMode[`traceMode`]

==== Additions to `pkl:reflect`

* {uri-stdlib-reflectModule}/Class#allMethods[`Class.allMethods`]
* {uri-stdlib-reflectModule}/Class#allProperties[`Class.allProperties`]
* {uri-stdlib-reflectModule}/Property#allAnnotations[`Propterty.allAnnotations`]
* {uri-stdlib-reflectModule}/Propterty#allModifiers[`Propterty.allModifiers`]

==== New module: `pkl:pklbinary`

The `pkl:pklbinary` standard library module is added.

=== `pkl repl` improvements

The REPL now handles interrupts (Ctrl-C) in a more user-friendly way (https://github.com/apple/pkl/pull/1188[#1188]).

Instead of exiting immediately, it behaves like other REPLs:

* If the line is non-empty or in a continuation, the buffer is cleared.
* If the line is empty, print a message with instructions on exiting the REPL.
** If another interrupt is sent immediately after, exit.

== Breaking Changes [small]#💔#

Things to watch out for when upgrading.

=== Binary data handling `yaml.Parser`

link:{yaml-binary-scalar}[YAML binary scalars] are now parsed as link:{uri-stdlib-Bytes}[`Bytes`] values.
Prior versions of Pkl parsed binary scalars as link:{uri-stdlib-String}[`String`] values containing the base64-encoded binary data.

=== Minimum Kotlin version bump

For users of Pkl's Kotlin libraries, the minimum Kotlin version has been bumped to 2.1 (https://github.com/apple/pkl/pull/1232[#1232]).

=== New base module names: `BaseValueRenderer`, `BytesRenderer`

Two new names are introduced to the base module: `BaseValueRenderer`, and `BytesRenderer`.
That means that any code that currently references these names on implicit `this` will break (https://github.com/apple/pkl/pull/1203[#1203]).

To learn more about how this breaks code and how to fix it, see xref:0.29.adoc#new-base-module-names[New base module names] in 0.29's release notes.

=== `pkldoc` sites need to be migrated

Due to breaking changes made in pkldoc's data model, existing pkldoc websites must be migrated.

See <<pkldoc-migration>> for more details.

== Miscellaneous [small]#🐸#

* Dependency updates (https://github.com/apple/pkl/pull/1184[#1184], https://github.com/apple/pkl/pull/1225[#1225], https://github.com/apple/pkl/pull/1226[#1226], https://github.com/apple/pkl/pull/1228[#1228]).
* Enforce Pkl formatting of stdlib (https://github.com/apple/pkl/pull/1236[#1236], https://github.com/apple/pkl/pull/1253[#1253], https://github.com/apple/pkl/pull/1258[#1258], https://github.com/apple/pkl/pull/1278[#1278], https://github.com/apple/pkl/pull/1279[#1279]).
* Add internal IntelliJ plugin that's meant to assist with development of the Pkl codebase itself (https://github.com/apple/pkl/pull/1248[#1248]).
* Update CircleCI macOS instance type and Xcode version (https://github.com/apple/pkl/pull/1243[#1243], https://github.com/apple/pkl/pull/1244[#1244]).
* Disable multi-jdk testing when running on Windows ARM (https://github.com/apple/pkl/pull/1223[#1223]).
* Refine documentation for class `Any` (https://github.com/apple/pkl/pull/1194[#1194]).

== Bugs fixed [small]#🐜#

The following bugs have been fixed.

* Incorrect error message when refusing to read past root dir (https://github.com/apple/pkl/pull/1234[#1233]).
* Unicode U+7FFF character (翿) incorrectly parsed as EOF (https://github.com/apple/pkl/pull/1251[#1251]).
* Fallback certificates do not work in certain classloader setups (https://github.com/apple/pkl/pull/1198[#1199]).

== Contributors [small]#🙏#

We would like to thank the contributors to this release (in alphabetical order):

* https://github.com/bioball[@bioball]
* https://github.com/HT154[@HT154]
* https://github.com/netvl[@netvl]
* https://github.com/spyoungtech[@spyoungtech]
* https://github.com/srueg[@srueg]
* https://github.com/ssalevan[@ssalevan]
* https://github.com/stackoverflow[@stackoverflow]
