fix(register): always inline source maps in auto mode so debuggers work

[Brooooooklyn]

Problem

Fixes #1059 — after upgrading to @swc-node/register 1.12.0, the Node debugger stopped binding breakpoints (or landed on the wrong line). Downgrading to 1.11.1 fixed it.

Root cause

The auto source-map mode added in 1.12.0 decides whether to inline the map based on process.sourceMapsEnabled:

getSourceMapMode() "auto":
  process.sourceMapsEnabled ? { inline: true,  store: false }   // needs --enable-source-maps
                            : { inline: false, store: true }    // DEFAULT — no inline map

process.sourceMapsEnabled is false by default (only true with --enable-source-maps). Debuggers — VS Code, node --inspect — normally run without that flag, so auto mode picks store-only: it populates SourcemapMap for @swc-node/sourcemap-support to rewrite Error.stack, but emits no inline //# sourceMappingURL=.

The V8 inspector reads the inline map off the running code to bind breakpoints, and it does so regardless of --enable-source-maps (that flag only governs how Node rewrites Error.stack). With no inline map, breakpoints have nothing to bind to.

In 1.11.1 the inline map was emitted unconditionally, so the debugger always worked.

Fix

Auto mode now always inlines the map, and additionally stores it only when native source maps are off (so Error.stack stays correct via @swc-node/sourcemap-support, without retaining a duplicate map when Node already handles stack traces):

-return process.sourceMapsEnabled ? { inline: true, store: false } : { inline: false, store: true }
+return process.sourceMapsEnabled ? { inline: true, store: false } : { inline: true,  store: true }

This restores the 1.11.1 behavior of always emitting an inline map. The explicit inline / store / none env modes (SWC_NODE_SOURCE_MAP_MODE) are unchanged.

Verification

• New regression test in register-runtime-tuning.spec.ts forces process.setSourceMapsEnabled(false) (the debugger-breaking condition) and asserts the emitted code carries an inline map and stores it. It fails on the old code, passes on the fix.
• Existing sourcemap integration test (correct stack-trace line numbers, Source maps broken since versions 1.10.1 (up to and including latest 1.10.9) #848/Incorrect stack traces with inline sourceMaps #861) still passes — store remains on when native maps are off.
• End-to-end: with sourceMap: true and no --enable-source-maps, the emitted code now contains an inline map and a thrown error reports the correct source line.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LXSDomd3mGu4SL4TJ9q6T2