fix(lint): modernize string and array checks with prefer-includes and prefer-string-starts-ends-with by joehan · Pull Request #11146 · firebase/firebase-tools

joehan · 2026-09-23T00:09:54Z

Description

Modernizes legacy indexOf and RegExp membership and prefix checks across the codebase to use standard String.prototype.includes, Array.prototype.includes, and String.prototype.startsWith. Promotes @typescript-eslint/prefer-includes and @typescript-eslint/prefer-string-starts-ends-with from "warn" to "error" in .eslintrc.js.

Resolves b/565073781 (parent goal b/565072516).

Changes

src/apphosting/backend.ts: Converted regex test on error code to maybeNodeError?.cause?.code?.includes("HANDSHAKE_FAILURE").
src/deploy/firestore/prepare.ts: Converted 5 targets.indexOf(...) >= 0 checks to targets.includes(...).
src/emulator/apphosting/serve.ts: Converted firebaseUtilPaths.indexOf(...) === -1 to !firebaseUtilPaths.includes(...).
src/emulator/auth/utils.ts: Converted /^\+/.test(phoneNumber) to phoneNumber.startsWith("+").
src/emulator/dataconnect/pgliteServer.ts: Converted regex test to err.message.includes("Database already exists").
src/emulator/download.ts: Converted file.indexOf(...) < 0 to !file.includes(...).
src/emulator/downloadableEmulators.ts: Converted regex test to (err.message ?? "").includes("Unknown system error").
src/firestore/validator.ts: Converted valid.indexOf(...) < 0 to !valid.includes(...).
src/profileReport.ts: Converted regex prefix test to !line.startsWith("data: ") and cleaned up unused constant.
.eslintrc.js: Promoted @typescript-eslint/prefer-includes and @typescript-eslint/prefer-string-starts-ends-with to "error".

Verification

ESLint: verified with 0 errors with rules set to "error".
Prettier: formatting verified.
npm run build: passed.
Mocha unit tests across all modified modules: passed (64 passing, 0 failing).

… prefer-string-starts-ends-with Modernizes legacy indexOf and RegExp membership/prefix checks to prefer-includes and prefer-string-starts-ends-with across 9 files. Promotes @typescript-eslint/prefer-includes and @typescript-eslint/prefer-string-starts-ends-with from 'warn' to 'error' in .eslintrc.js. b/565073781

gemini-code-assist

Code Review

This pull request modernizes string and array checks across the codebase by replacing regular expression tests and indexOf calls with modern alternatives like includes and startsWith, and updates ESLint rules to enforce these practices. The review feedback identifies three key issues: a type assertion mismatch in backend.ts where optional chaining is used on supposedly non-nullable types, a redundant nullish coalescing operator in downloadableEmulators.ts where a type guard already guarantees a string, and an off-by-one substring index bug in profileReport.ts resulting from the change to startsWith.

gemini-code-assist · 2026-09-23T00:11:43Z

  return (
    hasMessage(err) &&
-    /Unknown system error/.test(err.message ?? "") &&
+    (err.message ?? "").includes("Unknown system error") &&


Since hasMessage(err) is a type guard that guarantees err.message is a string, the nullish coalescing operator (?? "") is redundant. Removing it simplifies the expression and improves readability.

Suggested change

(err.message ?? "").includes("Unknown system error") &&

err.message.includes("Unknown system error") &&

Agreed, please fix

Addressed in commit d6542d9: Removed the redundant ?? "" fallback since hasMessage(err) type guard already guarantees that err.message is a string.

gemini-code-assist · 2026-09-23T00:11:43Z


 export function extractJSON(line: string, input: any): string | null {
-  if (!input && !DATA_LINE_REGEX.test(line)) {
+  if (!input && !line.startsWith("data: ")) {


Since the prefix check has been modernized to line.startsWith('data: ') (which is 6 characters long), the subsequent line.substring(5) on line 30 is now inconsistent as it leaves a leading space in the string before parsing. Consider updating it to line.substring(6) or line.slice(6) to cleanly remove the entire prefix.

Addressed in commit d6542d9: Updated line.substring(5) to line.substring(6) to correctly strip the 6-character "data: " prefix matching line.startsWith("data: "). Also added comprehensive unit tests for extractJSON covering SSE and non-SSE cases in src/profileReport.spec.ts.

…5073781)

joehan · 2026-10-01T22:43:05Z

+        "@typescript-eslint/prefer-includes": "error",
        "@typescript-eslint/prefer-regexp-exec": "warn", // TODO(bkendall): remove, allow to error.
-        "@typescript-eslint/prefer-string-starts-ends-with": "warn", // TODO(bkendall): remove, allow to error.
+        "@typescript-eslint/prefer-string-starts-ends-with": "error",


Please remove so that this just falls back to the default

Removed @typescript-eslint/prefer-string-starts-ends-with from .eslintrc.js in commit 4abdb0b so that it falls back to the recommended default.

joehan · 2026-10-01T22:43:09Z

        "@typescript-eslint/no-use-before-define": ["warn", { functions: false, typedefs: false }], // TODO(bkendall): change to error.
        "@typescript-eslint/no-var-requires": "warn", // TODO(bkendall): remove, allow to error.
-        "@typescript-eslint/prefer-includes": "warn", // TODO(bkendall): remove, allow to error.
+        "@typescript-eslint/prefer-includes": "error",


Please remove so that this just falls back to the default

Removed @typescript-eslint/prefer-includes from .eslintrc.js in commit 4abdb0b so that it falls back to the recommended default.

…task-modernize-string-and-array-che

…des to use defaults (b/565073781)

…nd-array-che

joehan self-assigned this Sep 23, 2026

gemini-code-assist Bot reviewed Sep 23, 2026

View reviewed changes

fix: address PR review feedback on PR #11146 and sync with main (b/56…

d6542d9

…5073781)

joehan commented Oct 1, 2026

View reviewed changes

joehan added 2 commits October 1, 2026 22:50

Merge remote-tracking branch 'origin/main' into ai-improve-565073781-…

bab7cb5

…task-modernize-string-and-array-che

fix: remove prefer-includes and prefer-string-starts-ends-with overri…

4abdb0b

…des to use defaults (b/565073781)

joehan marked this pull request as ready for review October 1, 2026 23:15

Merge branch 'main' into ai-improve-565073781-task-modernize-string-a…

b1d4a91

…nd-array-che

bkendall approved these changes Oct 1, 2026

View reviewed changes

joehan added 2 commits October 1, 2026 21:21

Merge branch 'main' into ai-improve-565073781-task-modernize-string-a…

3a8dec8

…nd-array-che

Merge branch 'main' into ai-improve-565073781-task-modernize-string-a…

78c0369

…nd-array-che

Navigation Menu

fix(lint): modernize string and array checks with prefer-includes and prefer-string-starts-ends-with - #11146

fix(lint): modernize string and array checks with prefer-includes and prefer-string-starts-ends-with#11146
joehan wants to merge 7 commits into
mainfrom
ai-improve-565073781-task-modernize-string-and-array-che

joehan commented Sep 23, 2026

Uh oh!

gemini-code-assist Bot left a comment

Uh oh!

Uh oh!

gemini-code-assist Bot Sep 23, 2026

Uh oh!

joehan Sep 30, 2026

Uh oh!

joehan Sep 30, 2026

Uh oh!

gemini-code-assist Bot Sep 23, 2026

Uh oh!

joehan Sep 30, 2026

Uh oh!

joehan Sep 30, 2026

Uh oh!

joehan Oct 1, 2026

Uh oh!

joehan Oct 1, 2026

Uh oh!

joehan Oct 1, 2026

Uh oh!

joehan Oct 1, 2026

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

	(err.message ?? "").includes("Unknown system error") &&
	err.message.includes("Unknown system error") &&

Conversation

joehan commented Sep 23, 2026

Description

Changes

Verification

Uh oh!

gemini-code-assist Bot left a comment

Choose a reason for hiding this comment

Code Review

Uh oh!

Uh oh!

gemini-code-assist Bot Sep 23, 2026

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist Bot Sep 23, 2026

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants