Throw the named error type from JSError.Throw*Error(string) by r-Larch · Pull Request #511 · microsoft/node-api-dotnet

René Larch (r-Larch) · 2026-10-21T20:14:45Z

Fixes #509.

Stacked on #510. This branch includes #510's two commits, because the test passes code and msg through the same unterminated buffers (without #510, code came back as ERR_TESTor). Only the last commit, "Throw the named error type from JSError.Throw*Error(string)", belongs to this PR. I'll rebase once #510 is merged.

JSError.ThrowTypeError, ThrowRangeError and ThrowSyntaxError (with and without code) all called JSRuntime.ThrowError, so JS received a plain Error. They now call the matching runtime method (napi_throw_type_error, napi_throw_range_error, node_api_throw_syntax_error).

Tests

NodejsEmbeddingTests.ThrowTypedError checks name, instanceof, message and code for Error, TypeError, RangeError and SyntaxError, with and without a code. The non-Error cases fail on main.

Local run (Windows x64, .NET SDK 10.0.402): net9.0 134/135 and net8.0 134/135. On net10.0 everything passed except napi-dotnet/overloads (hosted and AOT), which fails the same way on main. I could not run net472 locally.

🤖 Generated with Claude Code

The string buffer is rented from ArrayPool<byte>.Shared on .NET, which is not zeroed, so the byte reserved for each terminator could hold stale data and native code read argv entries past their end. Same fix as microsoft#482 (fixes microsoft#481); needed here because the new tests dirty the shared pool before the Node.js platform is created. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

PooledBuffer.FromStringUtf8 and FromSpanUtf8 reserved a byte for the terminator but never wrote it. On .NET the array comes from ArrayPool<byte>.Shared, which is not zeroed, so native functions that take a null-terminated const char* without a length read stale bytes past the string (or past the array): napi_throw_error / napi_throw_type_error / napi_throw_range_error / node_api_throw_syntax_error (code and msg), node_embedding_runtime_config_add_module and node_embedding_last_error_message_set. For example JSError.ThrowError("x") produced a JS error message of "x" followed by garbage, and a linked module could be registered under a corrupted name. - Write the terminator explicitly in both helpers. - Encode an empty string as just the terminator instead of returning PooledBuffer.Empty, which pinned to a null pointer (ThrowError("") passed msg = NULL, so napi_throw_error failed and nothing was thrown). A null string still maps to a null pointer. - Return the module-name buffer to the pool in EmbeddingRuntimeConfigAddModule (Node.js copies the name). Fixes microsoft#508. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

JSError.ThrowTypeError, ThrowRangeError and ThrowSyntaxError (with and without a code) all called JSRuntime.ThrowError, so JS received a plain Error instead of a TypeError / RangeError / SyntaxError. Call the matching runtime method instead. Fixes microsoft#509. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Copilot

🟢 Approval recommended

The focused fixes match the reported defects and include targeted regression coverage, with no unresolved findings.

No open issues 🎉

What changed in this PR

Fixes #509 by making typed JSError helpers throw the matching JavaScript error type. Includes the UTF-8 buffer fixes stacked from #510.

Changes:

Routes typed throw helpers to their matching runtime methods.
Explicitly terminates UTF-8 strings and disposes the module-name buffer.
Adds regression tests for error types and buffer handling.

File	Description
test/Utf8BufferTests.cs	Tests UTF-8 termination and null handling.
test/TestUtils.cs	Adds a helper to dirty pooled buffers.
test/NodejsEmbeddingTests.cs	Tests thrown error types, messages, and codes.
src/NodeApi/Runtime/Utf8StringArray.cs	Writes each string’s terminator explicitly.
src/NodeApi/Runtime/PooledBuffer.cs	Terminates UTF-8 buffers and distinguishes empty from null.
src/NodeApi/Runtime/NodejsRuntime.Embedding.cs	Disposes the module-name buffer.
src/NodeApi/JSError.cs	Calls the matching typed runtime throw methods.

_{Review effort: Balanced}

René Larch (r-Larch) · 2026-10-21T20:19:35Z

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René Larch (r-Larch) and others added 3 commits October 21, 2026 21:01

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Throw the named error type from JSError.Throw*Error(string) - #511

Throw the named error type from JSError.Throw*Error(string)#511
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