Restore tsgo exit code for noEmit type errors

[Copilot]

tsgo --noEmit started returning process exit code 1 for type errors after the internal ExitStatus values changed. tsc and previous tsgo releases return 2 for the same diagnostic path.

Analysis

The exit code derives from the ExitStatus: DiagnosticsPresent_OutputsSkipped (exit 1) vs DiagnosticsPresent_OutputsGenerated (exit 2). The status logic in internal/execute/tsc/emit.go already mirrors tsc (emitSkipped && diagnostics -> OutputsSkipped, else OutputsGenerated), so the bug was the wrong EmitSkipped value. tsgo's per-file emitters set EmitSkipped = true for noEmit, but tsc's handleNoEmitOptions only treats a single-file noEmit as skipped; a whole-program noEmit reports emitSkipped: false.

Fix

Port handleNoEmitOptions into Program.Emit: short-circuit noEmit before the per-file emitters and return EmitSkipped: options.TargetSourceFile != nil (false for a whole-program emit, true for a single file). This restores DiagnosticsPresent_OutputsGenerated for tsgo --noEmit and converges the tsc/noEmit baselines with upstream.

The change is scoped to the non-incremental path that the reported scenario uses; the shared incremental path (also used by build mode, whose status is derived differently upstream) is left unchanged.

Regression coverage

Reverted the earlier cmd/tsgo exit-code mapping hack and its non-tsc test, and added a tsc command-line regression test (noEmit with type error).

[jakebailey]

@copilot this seems totally random and hacky and not at all related to what the old compiler did, and the test case is not good as it's not a tsc test

rethink this entirely

[Copilot]

@copilot this seems totally random and hacky and not at all related to what the old compiler did, and the test case is not good as it's not a tsc test

rethink this entirely

Rethought in cc8ea69. The root cause is the EmitSkipped value, not the exit-code mapping: tsc's handleNoEmitOptions only treats a single-file noEmit as skipped, while a whole-program noEmit reports emitSkipped: false (so diagnostics give DiagnosticsPresent_OutputsGenerated). tsgo's per-file emitters were setting EmitSkipped = true for noEmit. I ported handleNoEmitOptions into Program.Emit, reverted the cmd/tsgo hack and its test, and added a tsc command-line test (noEmit with type error). The tsc/noEmit baselines now converge with upstream.

[jakebailey]

@copilot Isn't this strange? What files were generated?

[Copilot]

It's strange, but it matches tsc: no files are generated. DiagnosticsPresent_OutputsGenerated is just a misnomer here.

For a whole-program --noEmit, tsc's handleNoEmitOptions (with sourceFile === undefined) returns program.emitBuildInfo(...). In a non-incremental program there's no buildInfo path, so emitFiles writes nothing and emitBuildInfo bails out early without setting emitSkipped, which is initialized to false. So the result is emitSkipped: false with zero emitted files, and emitFilesAndReportErrorsAndGetExitStatus falls into the diagnostics.length > 0 branch -> DiagnosticsPresent_OutputsGenerated (exit code 2).

The corresponding upstream baseline shows the same thing: no *new* files, yet exitCode:: ExitStatus.DiagnosticsPresent_OutputsGenerated (_submodules/TypeScript/tests/baselines/reference/tsc/noEmit/multiFile/semantic-errors.js:54). The single-file case is the only one tsc treats as skipped (emitSkippedWithNoDiagnostics), which is why the port returns EmitSkipped: options.TargetSourceFile != nil.

[Copilot]

Pull request overview

Restores tsgo’s exit-code behavior for --noEmit runs with diagnostics by aligning Program.Emit’s EmitSkipped semantics with upstream tsc (whole-program noEmit should not count as “emit skipped”, preserving exit status DiagnosticsPresent_OutputsGenerated).

Changes:

• Short-circuit Program.Emit for noEmit and set EmitSkipped based on whether a target source file was specified.
• Add a command-line regression test scenario for --noEmit with a type error.
• Update tsc baseline outputs (notably ExitStatus and trace emit spans) to match the corrected behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/compiler/program.go	Implements noEmit short-circuit in Program.Emit, setting EmitSkipped to match tsc’s single-file vs whole-program behavior.
internal/execute/tsctests/tsc_test.go	Adds a new command-line test case covering --noEmit with a type error.
testdata/baselines/reference/tsc/commandLine/noEmit-with-type-error.js	New baseline validating exit status DiagnosticsPresent_OutputsGenerated for tsgo --noEmit index.ts with a type error.
testdata/baselines/reference/tsc/noEmit/syntax-errors.js	Updates expected ExitStatus for --noEmit syntax-error scenarios to DiagnosticsPresent_OutputsGenerated.
testdata/baselines/reference/tsc/noEmit/semantic-errors.js	Updates expected ExitStatus for --noEmit semantic-error scenarios to DiagnosticsPresent_OutputsGenerated.
testdata/baselines/reference/tsc/noEmit/dts-errors.js	Updates expected ExitStatus for --noEmit declaration-related error scenarios to DiagnosticsPresent_OutputsGenerated.
testdata/baselines/reference/tsc/generateTrace/generateTrace-with-multiple-files-and-complex-types.js	Updates expected ExitStatus and trace output to reflect the corrected noEmit/emit-skipped behavior.
testdata/baselines/reference/tsc/generateTrace/generateTrace-generates-types-file.js	Updates trace output to reflect the corrected noEmit/emit-skipped behavior.