version: "1.0.1" name: "compat-fixer" description: "Handles Plugin Verifier results and IDEA compatibility issues per the project compat policy. Invoke when the CI 'Plugin Verifier' job fails on the since-build deprecation gate, when the verifyPlugin task itself fails (internal or override-only API usage, compatibility problem), when a user reports a crash or breakage on a new IDEA version, when pluginSinceBuild is being raised, or when choosing which platform API to call."

Compat Fixer

Policy owner skill for IntelliJ platform compatibility. Reactive entry point: CI verifier failure, a P0 breakage report, or a since-build boundary bump.

The policy (single source of truth)

• The only gate: the since-build IDE (currently 252, pluginSinceBuild in

gradle.properties) must report zero deprecated API usages in the Plugin Verifier results. Enforced by the "Check since-build deprecations" step in .github/workflows/ci.yml (which also fails if the verifier matrix stops covering the since-build at all).

• Deprecations reported only on newer IDEs are observation-only. Do not fix

them now, do not build compat layers (reflection dispatch, dual source sets, build-number branching) for them. They become mandatory the moment pluginSinceBuild is raised past the point where a replacement API exists.

• When choosing a platform API while writing code, the criterion is: not

deprecated in the since-build SDK. Deprecation in a newer SDK alone is not a defect.

• Hard failures regardless of IDE (enforced by verifyPlugin itself via

failureLevel in build.gradle.kts): compatibility problems, internal-API usages, override-only-API usages. These red the gradle task directly — never add them to failureLevel exclusions to "fix" a warning.

Running the gate locally

CI runs the verifier on JDK 21. The verifier downloads every IDE in the matrix, so the first run takes a while — run it in the background.

./gradlew verifyPlugin --stacktrace 2>&1 | tee /tmp/verifier-stdout.log
since=$(sed -n 's/^pluginSinceBuild=//p' gradle.properties | tr -d '[:space:]')
grep -E "^Plugin .* against [A-Z]+-${since}\.[0-9.]+: " /tmp/verifier-stdout.log

The gate passes when that last command prints at least one line and none of them contain N usage(s) of deprecated API with N ≥ 1. Per-usage detail (class, method, the deprecated member) is under build/reports/pluginVerifier/ locally, or in the plugin-verification-reports artifact on CI.

Workflow A — CI gate failed (since-build has deprecations)

1. Read the failing job log. The gate prints the matched summary line, e.g.

Plugin ... against IC-252.x: Compatible. N usages of deprecated API. Find each usage in the reports (see above).

1. For each reported usage, find a replacement **that exists in the

since-build SDK** and migrate to it directly — no version branching. Check the replacement's own @Deprecated / @ApiStatus.Internal status in the since-build SDK before using it.

1. If no non-deprecated replacement exists in the since-build SDK, do not

invent a compat layer. Evaluate raising pluginSinceBuild (Workflow C) or, as a last resort, an issue note explaining the accepted exception.

1. Run the gate locally, run the tests that cover the touched code, then

commit with the fix(compat): <subject> conventional-commit format (see the git-commit skill), e.g. fix(compat): drop deprecated URL(String) and Messages.showChooseDialog.

Workflow B — breakage reported on a newer IDEA (P0/P1)

Classify first: crash / NoSuchMethodError / feature dead = P0; silently wrong behavior = P1. Both block release on any matrix IDE. Fix priority ladder:

1. Fix directly (adapt to the new API/behavior at the breakage site).
2. Raise `pluginSinceBuild` (Workflow C) if the fix is materially cheaper

on the newer baseline.

1. Temporary `until-build` cap only if neither works — record a removal

condition in the issue.

Never pre-emptively add dispatch layers for deprecation (see policy); this ladder is for actual removal/breakage only.

Workflow C — raising pluginSinceBuild

Editing gradle.properties pluginSinceBuild is a compat event, not just a version bump:

1. The Verifier matrix is ides { recommended() } in build.gradle.kts. It

usually includes the since-build, but that is a JetBrains-side data set, not a guarantee: after the bump, the CI gate asserts that a Plugin ... against <PRODUCT>-<newSince>.<build>: ... summary line exists and fails if none does. If the gate reports that, add the missing IDE explicitly to the ides { ... } block in build.gradle.kts rather than assuming recommended() covers it.

1. Run ./gradlew verifyPlugin. **Every deprecation now on the new since-build

line is a required fix in this same PR** — prior "observation-only" warnings are settled here.

1. Remove any compat workarounds whose minimum supported version they covered

(grep for compat commits / build-number guards).

1. Keep script/package.sh legacy best-effort builds for users below the new

boundary; the mainline no longer verifies those ranges.

Workflow D — verifyPlugin itself failed (hard failure)

The verify plugin step is red (not the deprecation gate): the verifier found a compatibility problem, an internal-API usage or an override-only-API usage on some matrix IDE. These are defects on every IDE, not just new ones.

1. Find the failing IDE and the exact member in the verifier output / reports.
2. Internal API (@ApiStatus.Internal, *Impl classes, internal

services): replace it with the public API that does the same job, e.g. the internal MessagesService → Messages.showDialog.

1. Override-only API (@ApiStatus.OverrideOnly): stop calling it

directly; call the public entry point that dispatches to it.

1. Compatibility problem (missing class/method on a matrix IDE): treat it

as a breakage — Workflow B.

1. Never silence it through failureLevel in build.gradle.kts.

Anti-patterns (forbidden)

• Reflection / ApplicationInfo.build dispatch / dual source sets introduced to

silence a newer-IDE deprecation warning.

• "Fixing" a newer-IDE-only deprecation by switching to an API absent from the

since-build SDK (turns a warning into a crash for the oldest users).

• Treating the GitHub ::warning:: from "Surface deprecated API usages as

warnings" as a to-do item.