`--incremental`: diagnostics caused by a JSON module are never cleared after the JSON file is fixed (7.0.2)

[jmelahman]

🔎 Search Terms

incremental json stale diagnostics, resolveJsonModule incremental, tsbuildinfo stale error json, semanticDiagnosticsPerFile json, incremental diagnostics not cleared

🕗 Version & Regression Information

• Broken in: typescript@7.0.2 (tsc -p . with "incremental": true)
• Still broken in nightly: typescript@7.1.0-dev.20260825.1 (identical repro output)
• Works in: typescript@5.9.3 — the identical file cycle clears the error correctly
• Not expressible in the Playground (requires --incremental state across multiple compilations)

💻 Code

Three files:

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "noEmit": true,
    "incremental": true,
    "resolveJsonModule": true,
    "esModuleInterop": true
  }
}

data.json

{ "title": "hello" }

check.ts

import type data from "./data.json";

type Shape = { title: string };
type Covers<T extends Shape> = T;

export type Check = Covers<typeof data>;

Repro steps:

rm -f tsconfig.tsbuildinfo
printf '{ "title": "hello" }\n' > data.json
tsc -p .    # 1. cold run: clean ✅

printf '{ }\n' > data.json
tsc -p .    # 2. warm run: TS2741 — correct ✅

printf '{ "title": "fixed" }\n' > data.json
tsc -p .    # 3. warm run: STILL TS2741 ❌ — data.json on disk has "title"

rm -f tsconfig.tsbuildinfo
tsc -p .    # 4. identical files, cache deleted: clean ✅

🙁 Actual behavior

Step 3 keeps failing on every subsequent run:

check.ts(6,28): error TS2741: Property 'title' is missing in type '{}' but required in type 'Shape'.

The diagnostic describes content that no longer exists ('{}' — the file contains "title": "fixed"). No edit to the JSON file ever clears it — neither new valid content nor restoring the original bytes. Only deleting tsconfig.tsbuildinfo (or turning off incremental) recovers. Note the asymmetry: the JSON change that introduces the error (step 2) is detected on a warm run; only clearing is broken.

Diffing tsconfig.tsbuildinfo between steps 2 and 3 shows the mechanism: the only change is data.json's content-hash version in fileInfos — so the changed JSON was registered — but the semanticDiagnosticsPerFile entry for check.ts still holds the old TS2741 ("messageArgs": ["title", "{}", "Shape"]) and is replayed instead of the file being re-checked.

The same behavior reproduces with a value import (import data from "./data.json"), with "moduleResolution": "bundler", and in a large real project (Next.js app where locale JSON catalogs are type-checked against en.json — fixing the catalog after a failing check strands the build red until the buildinfo is deleted).

🙂 Expected behavior

Step 3 exits clean, as typescript@5.9.3 does for the identical sequence: fixing the JSON module re-checks its dependents and clears the cached diagnostics.

Additional information

Related but distinct: microsoft/typescript-go#2666 covers missing invalidation for changed external dependencies; this report is in-project JSON modules, where the changed file's hash is visibly updated in the buildinfo yet dependents' cached diagnostics are not invalidated.

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Disclosure: this issue was investigated and written by Claude (Anthropic's AI assistant), working in Claude Code on behalf of the reporter. The repro and the 5.9.3/7.0.2 comparison were executed and verified, not inferred.