fix: avoid activating Java during debug configuration discovery

[wenyt (wenytang-ms)]

Summary

Fixes #1703.

Keep debug configuration discovery in non-Java workspaces from starting or waiting for redhat.java. This is a focused fix based on current main, independent of #1696's background-initialization and AI-readiness redesign.

Cause

VS Code can activate this extension through the global onDebugInitialConfigurations event. Two startup paths then unnecessarily activate Java:

• No-Config terminal initialization awaits getJavaHome() before activation can complete.
• Stack-trace link-provider initialization calls getJavaExtensionAPI() even without a Java file.

Additionally, the async Promise executor in getJavaExtensionAPI() loses activation rejections, leaving the outer promise pending instead of reaching callers' error handlers. This provides a failure path consistent with the reported JDK prompt and stuck extension activation; the reporter's exact Java startup failure is not yet confirmed.

Changes

• Remove Java activation from No-Config preparation. Endpoint watching and wrapper/PATH setup remain available without a Java API.
• Add a disposable, one-shot passive activation observer. It reads exports only after isActive, never calls activate(), and stops after delivery/error or disposal. It checks once per second while waiting because VS Code has no public extension-activation event.
• Use that observer for optional VSCODE_JAVA_EXEC discovery and stack-trace links. Preserve stack-trace Standard-mode gating and support Java opening later in the same window.
• Reuse the observer for source-invalidation subscriptions, replacing the existing unowned 30-minute polling loop and owning the resulting subscription.
• Propagate Java activation rejection correctly. Preserve caller cancellation without cancelling shared Java activation, and release cancellation listeners.
• Preserve the No-Config opt-out, cached executable fallback, diff-aware environment updates, endpoint protocol, and existing AI launch behavior from fix: stop recommending automatic Java launch retries #1701.

Existing terminals need recreation to receive a Java executable discovered later. Explicit Java Run/Debug continues to activate Java normally.

Validation

• npm run compile.
• Targeted TSLint on all changed TypeScript files.
• Focused suites in an isolated Windows VS Code 1.95.3 extension host: 61 passed, 1 POSIX-only test skipped.
• The activation regression keeps a fake Java activation promise pending: core provider/adapter/commands register, terminal setup finishes, and Java activation is called zero times. After simulated natural activation, executable discovery, stack-trace registration, and source-invalidation subscription complete.
• Additional coverage includes activation rejection, cancellation/listener cleanup, cached fallback, later activation/disposal, storage errors, endpoint attachment dispatch, settings/AI opt-out, and environment updates.

Java-extension behavior and registration boundaries are stubbed in the activation test; it does not claim reporter-environment reproduction, an automated picker UI test, or a real JVM attach. No dependency, manifest activation-event, AI-readiness, or endpoint-protocol redesign is included.

[Copilot]

Copilot review overview

🟢 Approval recommended

The implementation matches the reported activation issue and includes focused lifecycle and regression coverage.

Review effort: Balanced
Findings: None

What changed in this PR

Prevents Java activation from blocking debug configuration discovery in non-Java workspaces.

Changes:

• Adds passive, disposable Java activation observation.
• Updates No-Config, stack-trace, and source-invalidation integrations.
• Fixes activation rejection/cancellation handling and adds regression coverage.

File	Description
src/​utility.ts	Adds passive activation observation and fixes promise handling.
src/​noConfigDebugInit.ts	Removes Java activation from terminal preparation.
src/​stackTraceLinkProvider.ts	Defers link registration until natural Java activation.
src/​extension.ts	Uses owned passive source-invalidation subscription.
test/​javaExtensionAPI.test.ts	Covers rejection and cancellation behavior.
test/​javaDebugActivation.test.ts	Verifies non-Java activation remains unblocked.
test/​noConfigDebugStorage.test.ts	Covers deferred executable discovery and disposal.
README.md	Documents deferred Java executable discovery.
bundled/​scripts/​noConfigScripts/​README.md	Documents wrapper behavior and selection order.

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