baseline-java-versions: `javaCompiler` property to compile Java code with a certain JDK version #3342

CRogers · 2025-11-07T17:44:55Z

Before this PR

Currently when compiling Java code, if we want to target Java major version XX bytecode in class files, we'll use an XX Java compiler. We do not use the --release flag (which would allow us to target a lower source/bytecode/jdk api from a higher versioned Java compiler) because it's is verboten to use --release with --add-exports, which happens a lot around our codebases.

Error Prone 2.43.0 has made JDK 21 the minimum required JDK that Error Prone is run in. The recommendation is to use --release so a higher version JDK can safely output java classes at a lower language level. However, we can't do this due to the aforementioned issue with --add-exports. Similarly, we're stuck on Java 17 libraries for now, so can't just upgrade everything to Java 21. This makes us stuck, unable to upgrade Error Prone.

Luckily, in a previous PR I have removed the --release/--add-exports restriction (it also has more details about the errorprone issue). There is nothing stopping us using a higher compiler and targeting a lower version using --release.

After this PR

==COMMIT_MSG==
baseline-java-versions: Introduce a required javaCompiler property to javaVersions which will determine which JDK is used to run the Java compiler. --release is now used to target lower Java language versions/class file bytecode than the compiler.
==COMMIT_MSG==

I've expanded the tests quite a lot.

Possible downsides?

The groovy and scala codepaths in this plugins were/are also entirely untested. I've mostly left them be.
Needs some more manual testing.
We will need to excavate out the compiler property as part of baseline upgrades.

changelog-app · 2025-11-07T17:44:58Z

Generate changelog in `changelog/@unreleased`

Type (Select exactly one)

Feature (Adding new functionality)
Improvement (Improving existing functionality)
Fix (Fixing an issue with existing functionality)
Break (Creating a new major version by breaking public APIs)
Deprecation (Removing functionality in a non-breaking way)
Migration (Automatically moving data/functionality to a new system)

Description

baseline-java-versions: Introduce a required javaCompiler property to javaVersions which will determine which JDK is used to run the Java compiler. --release is now used to target lower Java language versions/class file bytecode than the compiler.

Check the box to generate changelog(s)

Generate changelog entry

CRogers · 2025-11-07T17:45:58Z

...java/com/palantir/baseline/plugins/javaversions/SubprojectBaselineJavaVersionsExtension.java

+
    @Override
    public final void setLibraryTarget(int _value) {
-        throw throwCannotSetFromSubproject();


Hilariously this is throwing the result of a method that always throws.

…one 21 issue?

…` now

CRogers · 2025-11-07T23:45:33Z

README.md

 The configurable fields of the `javaVersions` extension are:
-* `libraryTarget`: (required) The Java version used for compilation of libraries that are published.
-* `distributionTarget`: (optional) The Java version used for compilation of code used within distributions, but not published externally. Defaults to the `libraryTarget` version.
+* `compiler`: (required) The version of the Java compiler used. 


I wonder if this should be javaCompiler to make clear this version is not being used for groovy/scala compilation

CRogers · 2025-11-07T23:47:18Z

README.md

 The configurable fields of the `javaVersions` extension are:
-* `libraryTarget`: (required) The Java version used for compilation of libraries that are published.
-* `distributionTarget`: (optional) The Java version used for compilation of code used within distributions, but not published externally. Defaults to the `libraryTarget` version.
+* `compiler`: (required) The version of the Java compiler used. 


I have made this required because if it is not, everything remains unset and Gradle defaults to using the daemon JDK version, which seems not ideal. But it does mean it always needs to be set, even if your project only has groovy/scala and no java.

CRogers · 2025-11-07T23:49:25Z

...eline-java/src/main/java/com/palantir/baseline/plugins/javaversions/BaselineJavaVersion.java

-        }
-
-        // In Gradle <8, we need to set sourceCompatibility to opt out of '-release', allowing opens/exports to be used.
-        // https://github.com/gradle/gradle/issues/18824#issuecomment-1026909824


Pretty sure this is irrelevant after #3324. But really need some tests (currently the new tests do not even test against Gradle 7). I'm not even sure groovy/scala have --add-exports at compilation time.

CRogers · 2025-11-08T00:09:14Z

...eline-java/src/main/java/com/palantir/baseline/plugins/javaversions/BaselineJavaVersion.java

            groovyCompileTask
                    .getOptions()
                    .getCompilerArgumentProviders()
                    .add(new EnablePreviewArgumentProvider(target));


Unsure if this actually does anything for Groovy compile. Same for Scala. Needs more testing. Might need it to be able to compile against preview APIs (maybe use Java preview source features when compiling with Java files with Groovy?)

I guess not really relevant for this PR.

CRogers · 2025-11-08T00:24:46Z

README.md

 apply plugin: 'com.palantir.baseline-java-versions'

 javaVersions {
+    javaCompiler = 25


We'll need to excavate this (javaCompiler = 21) out.

CRogers · 2025-11-25T16:35:11Z

gradle-baseline-java/src/main/java/com/palantir/baseline/plugins/Baseline.java

            proj.getPluginManager().apply(BaselineReproducibility.class);
            proj.getPluginManager().apply(BaselineClassUniquenessPlugin.class);
            proj.getPluginManager().apply(BaselineExactDependencies.class);
-            proj.getPluginManager().apply(BaselineReleaseCompatibility.class);


This would set --release on Java <9, but we always set --release now so it's no longer needed.

…llumr/separate-compiler-config

CRogers added 2 commits November 7, 2025 17:42

Add compiler to extensions

6e4407f

Save

7939bff

CRogers commented Nov 7, 2025

View reviewed changes

CRogers added 18 commits November 7, 2025 20:57

Fix tests

00998df

compielr plugin for testing

d59c317

Test for good error message

788f1d6

Better errors

ce34ee5

Some javadoc tests

d3eed1f

Ensure --release works as expected

a7f506f

We don't actually need javadoc comments to run javadoc

d4e432f

More javadoc checks

22c7b3f

Closer to getting groovy right

db11599

apparently release does nothing in scala too

11a2111

Actually test groovy properly

173b2af

unfuck scala. someone should really write tests

9b49ea2

why change javadoc when it works already and doesn't have the errorpr…

26f8bb1

…one 21 issue?

Delete BaselineReleaseCompatibility - we're always setting `--release…

0fff24a

…` now

clearer names

f02ad36

delete lies

59db20b

oops

c86f58a

Delete docs

503a95c

CRogers changed the title ~~baseline-java-versions: compiler property to compile code with a certain JDK version~~ baseline-java-versions: compiler property to compile Java code with a certain JDK version Nov 7, 2025

Update README.md

3ecd381

CRogers commented Nov 7, 2025

View reviewed changes

CRogers added 2 commits November 8, 2025 00:07

Note groovy compile api weirdness

e67ecda

paren

fe91c2e

CRogers commented Nov 8, 2025

View reviewed changes

CRogers added 3 commits November 8, 2025 00:15

comment

898c814

It's javaCompiler now

95777b9

more references

e736983

CRogers changed the title ~~baseline-java-versions: compiler property to compile Java code with a certain JDK version~~ baseline-java-versions: javaCompiler property to compile Java code with a certain JDK version Nov 8, 2025

CRogers commented Nov 8, 2025

View reviewed changes

CRogers commented Nov 25, 2025

View reviewed changes

CRogers added 5 commits November 25, 2025 16:36

compiler -> javaCompiler

d2a0fd9

fix some tests

1886a74

Merge branch 'develop' of github.com:palantir/gradle-baseline into ca…

c3c0e99

…llumr/separate-compiler-config

Fix nullaway test again

6ca62af

Actually do something vaguely sensible

437f0f9

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

baseline-java-versions: `javaCompiler` property to compile Java code with a certain JDK version #3342

baseline-java-versions: `javaCompiler` property to compile Java code with a certain JDK version #3342

Uh oh!

CRogers commented Nov 7, 2025 •

edited

Loading

Uh oh!

changelog-app bot commented Nov 7, 2025 •

edited by CRogers

Loading

Uh oh!

CRogers Nov 7, 2025

Uh oh!

CRogers Nov 7, 2025

Uh oh!

CRogers Nov 8, 2025

Uh oh!

CRogers Nov 7, 2025

Uh oh!

CRogers Nov 7, 2025 •

edited

Loading

Uh oh!

CRogers Nov 8, 2025 •

edited

Loading

Uh oh!

CRogers Nov 8, 2025

Uh oh!

CRogers Nov 8, 2025

Uh oh!

CRogers Nov 25, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

baseline-java-versions: javaCompiler property to compile Java code with a certain JDK version #3342

Are you sure you want to change the base?

baseline-java-versions: javaCompiler property to compile Java code with a certain JDK version #3342

Uh oh!

Conversation

CRogers commented Nov 7, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Before this PR

After this PR

Possible downsides?

Uh oh!

changelog-app bot commented Nov 7, 2025 • edited by CRogers Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Generate changelog in changelog/@unreleased

Uh oh!

CRogers Nov 7, 2025

Choose a reason for hiding this comment

Uh oh!

CRogers Nov 7, 2025

Choose a reason for hiding this comment

Uh oh!

CRogers Nov 8, 2025

Choose a reason for hiding this comment

Uh oh!

CRogers Nov 7, 2025

Choose a reason for hiding this comment

Uh oh!

CRogers Nov 7, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

CRogers Nov 8, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

CRogers Nov 8, 2025

Choose a reason for hiding this comment

Uh oh!

CRogers Nov 8, 2025

Choose a reason for hiding this comment

Uh oh!

CRogers Nov 25, 2025

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

baseline-java-versions: `javaCompiler` property to compile Java code with a certain JDK version #3342

baseline-java-versions: `javaCompiler` property to compile Java code with a certain JDK version #3342

CRogers commented Nov 7, 2025 •

edited

Loading

changelog-app bot commented Nov 7, 2025 •

edited by CRogers

Loading

Generate changelog in `changelog/@unreleased`

CRogers Nov 7, 2025 •

edited

Loading

CRogers Nov 8, 2025 •

edited

Loading