Path mappings parsing uses too much memory for projects with many references and paths

[auvred]

Acknowledgement

• I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

Comment

Reproduction:

1. Clone the kibana repo

   cd /tmp
   git clone --depth https://github.com/elastic/kibana
   cd kibana
   yarn
   yarn kbn bootstrap
   code .

2. Generate typecheck tsconfigs:

   node scripts/type_check.js

   Don't wait for the script to finish.
   Once you see info starting [tsc] > node_modules/typescript-7/bin/tsc -b tsconfig.refs.json --builders 6 --checkers 3 --pretty in output, you can ctrl-c it.

3. Put "js/ts.customConfigFileName": "tsconfig.type_check.json", into .vscode/settings.json

4. Open src/core/packages/chrome/browser/src/nav_links.ts

5. Locate category?: AppCategory and request Find All References on category

6. Run Developer: TypeScript: Save Heap Profile

7. Open alloc_space flamegraph

---

For projects like Kibana with a lot of compilerOptions.paths, allocating ParsedPatterns for every module resolution consumes too much memory.

TypeScript/tsc/internal/module/resolver.go

Lines 2011 to 2044 in 8ac035a

	func TryParsePatterns(pathMappings *collections.OrderedMap[string, []string]) *ParsedPatterns {
	paths := pathMappings.Keys()
	numPatterns := 0
	for path := range paths {
	if pattern := core.TryParsePattern(path); pattern.IsValid() && pattern.StarIndex == -1 {
	numPatterns++
	}
	}
	numMatchables := pathMappings.Size() - numPatterns
	var patterns []core.Pattern
	var matchableStringSet collections.Set[string]
	if numPatterns != 0 {
	patterns = make([]core.Pattern, 0, numPatterns)
	}
	if numMatchables != 0 {
	matchableStringSet = *collections.NewSetWithSizeHint[string](numMatchables)
	}
	for path := range paths {
	if pattern := core.TryParsePattern(path); pattern.IsValid() {
	if pattern.StarIndex == -1 {
	matchableStringSet.Add(path)
	} else {
	patterns = append(patterns, pattern)
	}
	}
	}
	return &ParsedPatterns{
	matchableStringSet: matchableStringSet,
	patterns: patterns,
	}
	}