Shut down the command line's thread pool when formatting is done - #47
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Main.formatFiles created a fixed thread pool on every call and never shut it down. The command line does not notice, because the process exits, but a tool that runs Main in-process kept up to MAX_THREADS idle threads per call (#40, from google/google-java-format#384). The pool is now closed when formatFiles returns. On Java 21 ExecutorService is AutoCloseable, and close() waits for the submitted tasks, which formatFiles has already waited for by then. The new MainTest runs format from a thread of its own thread group, which the pool's threads join, and fails without the change because a pool thread is still running.
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Part of #40, split out of #45. Upstream report: google/google-java-format#384.
What changes
Main.formatFilescreated a fixed thread pool on every call and never shut it down. The command line did not notice, because the process exits, but a tool that runsMainin-process kept up toMAX_THREADSidle threads per call.The pool is now created in a try-with-resources. On Java 21
ExecutorServiceisAutoCloseable, andclose()waits for the submitted tasks, which have all been waited for by then. The old body moved unchanged into an overload that takes the pool, so it is not re-indented in the diff.Checked
MainTest.formatLeavesNoPoolThreadRunningrunsformatfrom a thread in a thread group of its own; the pool's threads join that group. Without the change it fails with "pool-1-thread-1 is still running"../gradlew :open-java-format:teston JDK 21: 1448 tests, all green.