[hi-ogawa]

• closes Optimize html reporter module graph data #9763
• alternative: fix(ui): dedupe module graph in html reporter #11419
• repro: https://gist.github.com/hi-ogawa/ced83dcb817ffd8e96025b898edc0dc4

The html reporter stored a full ModuleGraphData per test file, so the report grew with test files × modules and crashed flatted.stringify with RangeError: Invalid string length. Now it stores the module graph the way the blob reporter does, once per project and Vite environment, and the static client derives each test file's graph on demand.

// before: moduleGraph[project][testFile], repeated for every test file
"/a.test.ts": { graph: { "/shared.ts": [], "/util.ts": ["/shared.ts"], "/a.test.ts": ["/util.ts"] }, ... }
"/b.test.ts": { graph: { "/shared.ts": [], "/util.ts": ["/shared.ts"], "/b.test.ts": ["/util.ts", "/dep.js"] }, ... }

// after: environmentModules[project], same data as the blob reporter
{
  environments: {
    ssr: {
      idTable: ["/a.test.ts", "/util.ts", "/shared.ts", "/b.test.ts", "/dep.js", ...],
      modules: [[0, 0, 0, [1]], [1, 1, 1, [2]], [2, 2, 2, []], [3, 3, 3, [1, 4]], ...], // [id, file, url, importedIds]
    },
  },
  external: [["/dep.js", "/dep.js"]],
  setupFiles: [],
}

blob reporter  ──┐
                 ├─ serializeProjectModules   (one on-disk format)
html reporter  ──┘
static client  ── deriveModuleGraphData(serialized, testFile)   (repeats getModuleGraph's classification)

Compared with #11419 (both measured on the same repro, before: 421 MB / 24 MB, 3.1 GB, RangeError):

	#10352	#11419
html graph data	raw environment graph, same as blob (serializeProjectModules)	classified ModuleGraphData + per-file roots
graph formats	1, shared with blob	blob format + html-only format
classification logic	2 copies: getModuleGraph + deriveModuleGraphData (test checks they agree)	1: createModuleGraphCollector; client only walks reachability
1000×3000 raw / gz	2.1 MB / 0.26 MB	2.5 MB / 0.23 MB
1000×3000 peak RSS	275 MB	263 MB
1000×5000 --merge-reports + html	0.67s	0.76s
behavior change	none	browser optimized deps in externalized lose ?v=hash (snapshot change)

On Vitest's own test/unit report the effect is small (graph 798 KB → 327 KB, total about 3%), because the files task data dominates there.

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[hi-ogawa]

Reviving the PR since this take looked more promising than #11419.

[hi-ogawa]

closing in favor of #11421