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Fix panic in declaration emit for named CommonJS exports from .cjs files#3354

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copilot/fix-reexporting-micromatch-crash
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Fix panic in declaration emit for named CommonJS exports from .cjs files#3354
Copilot wants to merge 6 commits intomainfrom
copilot/fix-reexporting-micromatch-crash

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Copilot AI commented Apr 6, 2026

Fix the missing diagnostic context in transformCommonJSExport for named non-default exports. Without this fix, declaration emit panics with "Diagnostic emitted without context" when a .cjs file re-exports a type that triggers a symbol accessibility check.

The test uses export = with a non-exported interface (ExtPkg), matching the original micromatch repro pattern. This triggers the symbol accessibility check that caused the panic. The test produces a TS4023 error due to a separate type serialization bug (tsgo emits ExtPkg instead of typeof import("extpkg")), but crucially no longer panics.

Verified: test panics without the fix and passes with it.

Copilot AI and others added 2 commits April 6, 2026 21:28
Panic: 'Diagnostic emitted without context' in declaration emit
for CommonJS non-default named exports from .cjs files.

Root cause: transformCommonJSExport's else branch (non-default
identifier exports) does not set getSymbolAccessibilityDiagnostic
before calling ensureType. When the type references symbols from
external modules that can't be named, throwDiagnostic panics.

The test reproduces the exact panic by creating a .cjs file that
re-exports a type whose expanded form references symbols from
another @types package.

Co-authored-by: jakebailey <5341706+jakebailey@users.noreply.github.com>
Copilot AI changed the title [WIP] Fix reexporting @types/micromatch@4.0.10 from a .cjs file crash Fix panic in declaration emit for named CommonJS exports from .cjs files Apr 6, 2026
Copilot AI requested a review from jakebailey April 6, 2026 21:33
Comment thread investigation_2522.md Outdated
@@ -0,0 +1,93 @@
# Investigation: Issue #2522 - Panic "Diagnostic emitted without context"
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@copilot delete this

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Deleted in 7a353b4.

Agent-Logs-Url: https://github.com/microsoft/typescript-go/sessions/5e11e9c5-7894-4a21-ad2b-f380d95d6ba0

Co-authored-by: jakebailey <5341706+jakebailey@users.noreply.github.com>
Copilot AI requested a review from jakebailey April 6, 2026 22:07
@@ -0,0 +1,40 @@
/test.cjs(2,1): error TS4023: Exported variable 'extpkg' has or is using name 'ExtPkg' from external module "/node_modules/@types/extpkg/index" but cannot be named.
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@copilot The original repro compiled without errors. This one seemingly does not. Is there some other bug that is causing us to be unable to name this?

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Yes, there's a separate bug. When a module uses export = extpkg where extpkg is typed as a non-exported interface (ExtPkg), tsgo's type serialization emits ExtPkg directly instead of typeof import("extpkg"). tsc correctly uses typeof import("extpkg") for the same scenario, avoiding the accessibility issue.

I've reworked the test in 5db02df to use directly-exported types (via export interface), which tsgo handles correctly. The test now compiles without errors, matching the original micromatch repro behavior. The export = type serialization issue is a separate bug.

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@copilot Except, your test does not crash if your changes to the internal dir are reverted! Think harder. You need a test that fails.

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You're right - the simplified test with directly-exported types never triggered the symbol accessibility check, so it would never call getSymbolAccessibilityDiagnostic and never panic.

Reworked the test in 86e36b4 to use export = with a non-exported interface (ExtPkg), matching the original micromatch pattern. Verified it panics without the fix and passes with it. The TS4023 error it produces is from a separate type serialization bug (tsgo emits ExtPkg instead of typeof import("extpkg")).

… from separate type serialization bug

Agent-Logs-Url: https://github.com/microsoft/typescript-go/sessions/0b996517-9938-4d32-b7dc-9f9a7b41eee1

Co-authored-by: jakebailey <5341706+jakebailey@users.noreply.github.com>
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Reexporting @types/micromatch@4.0.10 from a .cjs file crashes

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