[abhis3]

Important

Stacked on #713. Merge #713 first, then retarget this PR to main before merging. GitHub only retargets it automatically if #713's branch is deleted.

Problem

With CRASHLYTICS_UPLOAD_MAPPING=true, the adapter's modifyConfig sets productionBrowserSourceMaps: true. Nothing on Cloud Run uploads those maps to Crashlytics or removes them from the image yet. So GET /_next/static/chunks/*.js.map returns 200 with the full sourcesContent and Cache-Control: public, max-age=31536000, immutable, which publishes the app's client source.

Change

• modifyConfig no longer turns on productionBrowserSourceMaps for CRASHLYTICS_UPLOAD_MAPPING. When the env var is set (true or 1), it logs one warning:
  [adapter-nextjs] Warning: Ignoring CRASHLYTICS_UPLOAD_MAPPING=true: Crashlytics source-map upload isn't available on Cloud Run yet, and enabling browser source maps would serve the app's source publicly. NextConfig productionBrowserSourceMaps is left unchanged.
• The app's own productionBrowserSourceMaps setting (true or false) is never changed.
• A TODO marks where to turn this back on, once source maps are uploaded and stripped during the build.
• README: updates the "Browser source maps" bullet and the CRASHLYTICS_UPLOAD_MAPPING row.
• Tests: the Crashlytics test now checks that productionBrowserSourceMaps stays unset when the env var is true or 1, and that the warning is logged once. It also checks that a user's true or false is kept, with or without the env var, and that nothing is logged when the env var isn't set.

Testing

• npm test in packages/@google-cloud/adapter-nextjs, on Node 18.20.8 and Node 22.23.4: 44 passing, 11 pending. The pending ones are the SMOKE_TEST=1 suites, the same as on the base branch. npm run build is clean on both.
• npm run lint:quiet passes, with no new warnings in the touched files.

[gemini-code-assist]

Code Review

This pull request updates the Next.js adapter to ignore the CRASHLYTICS_UPLOAD_MAPPING environment variable and leave productionBrowserSourceMaps unchanged, logging a warning instead. This prevents the application's source maps from being served publicly from /_next/static since Crashlytics source-map upload is not yet supported on Cloud Run. The feedback suggests dynamically displaying the actual value of CRASHLYTICS_UPLOAD_MAPPING (e.g., '1' or 'true') in the warning message to avoid confusion, along with updating the corresponding test assertions.

[gemini-code-assist]

When CRASHLYTICS_UPLOAD_MAPPING is set to "1", the warning message still hardcodes CRASHLYTICS_UPLOAD_MAPPING=true, which can be confusing to users who configured it with "1".\n\nConsider dynamically including the actual value of the environment variable in the warning message to improve clarity.

      console.warn(\n        "[adapter-nextjs] Warning: Ignoring CRASHLYTICS_UPLOAD_MAPPING=" + process.env.CRASHLYTICS_UPLOAD_MAPPING + ": Crashlytics source-map upload isn't available on Cloud Run yet, and enabling browser source maps would serve the app's source publicly. NextConfig productionBrowserSourceMaps is left unchanged."\n      );

[gemini-code-assist]

Update the test assertions to match the dynamic warning message and verify that the actual value of CRASHLYTICS_UPLOAD_MAPPING is correctly reflected in the logs.

      const ignoredLogs = (): string[] =>\n        warnLogs.filter((w) => w.includes("Ignoring CRASHLYTICS_UPLOAD_MAPPING"));\n\n      for (const value of ["true", "1"]) {\n        process.env.CRASHLYTICS_UPLOAD_MAPPING = value;\n        warnLogs = [];\n        const result = modifyConfig<NextConfig>(deepFreeze({}), ctx);\n        assert.strictEqual(result.productionBrowserSourceMaps, undefined);\n        assert.strictEqual(ignoredLogs().length, 1);\n        assert.ok(ignoredLogs()[0].includes("Ignoring CRASHLYTICS_UPLOAD_MAPPING=" + value));\n        assert.ok(ignoredLogs()[0].includes("would serve the app's source publicly"));\n      }