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errors: remove source map rekey logic #39025

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errors: remove source map rekey logic #39025

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773ea75
errors: don't rekey on primitive type
Jun 13, 2021
0b67b1e
Update lib/internal/source_map/source_map_cache.js
Jun 13, 2021
9a7fad6
stop rekeying cjs cache
Jun 13, 2021
4af02fd
delete more code
Jun 13, 2021
b56a914
test: update test to reflect refactor
Jun 15, 2021
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errors: don't rekey on primitive type 
If an error is thrown before a module is loaded, we attempt to cache
source map against error object, rather than module object. We
can't do this if the error is a primitive type

Fixes #38945
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bcoe
bcoe committed Jun 13, 2021
commit 773ea75254a1d792a7adc59fb7945b380cb95d0f
6 changes: 5 additions & 1 deletion lib/internal/source_map/source_map_cache.js
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Expand Up @@ -175,7 +175,11 @@ function sourcesToAbsolute(baseURL, data) {
// Move source map from garbage collected module to alternate key.
function rekeySourceMap(cjsModuleInstance, newInstance) {
const sourceMap = cjsSourceMapCache.get(cjsModuleInstance);
if (sourceMap) {
// If an exception occurs before a module finishes loading it will removed
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// from the module cache and our WeakMap. To allow a source map to still be
// applied to the stack trace when this happens, we rekey on the thrown error.
// This is only possible if the error is an object and not a primitive type.
if (sourceMap && typeof newInstance === 'object') {

@aduh95 aduh95 Jun 13, 2021

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Could newInstance be null, and if so, wouldn't that cause an error? Can you add a test case please?

@bcoe bcoe Jun 13, 2021

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@aduh95 I did some testing it no longer seems like that rekey logic is needed to ensure that source maps are written to disk prior to exit. Perhaps this is because of refactors that have taken place related to source map serialization? Or perhaps a FinalizationRegistry fires on the next tick, such that the source map will be available while the process shuts down?

Either way, no tests fail if we simply remove the rekey logic.

@aduh95 aduh95 Jun 15, 2021

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Nice! I still think it'd be interesting to have a test case with a throw null for completeness sake.

cjsSourceMapCache.set(newInstance, sourceMap);
}
}
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8 changes: 8 additions & 0 deletions test/fixtures/source-map/throw-string-original.js
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@@ -0,0 +1,8 @@
/*
* comments dropped by uglify.
*/
function Hello() {
throw 'goodbye';
}

Hello();
2 changes: 2 additions & 0 deletions test/fixtures/source-map/throw-string.js
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17 changes: 17 additions & 0 deletions test/parallel/test-source-map-enable.js
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Expand Up @@ -307,6 +307,23 @@ function nextdir() {
assert.ok(sourceMap);
}

// Does not attempt to rekey source map on primitive type.
{
const coverageDirectory = nextdir();
const output = spawnSync(process.execPath, [
'--enable-source-maps',
require.resolve('../fixtures/source-map/throw-string.js'),
], { env: { ...process.env, NODE_V8_COVERAGE: coverageDirectory } });
const sourceMap = getSourceMapFromCache(
'throw-string.js',
coverageDirectory
);
// Original stack trace.
assert.match(output.stderr.toString(), /goodbye/);
// Source map should have been serialized.
assert.ok(sourceMap);
}

function getSourceMapFromCache(fixtureFile, coverageDirectory) {
const jsonFiles = fs.readdirSync(coverageDirectory);
for (const jsonFile of jsonFiles) {
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