fix: make regex opt‑in for search/replace #75

oekeur · 2026-01-28T16:01:37Z

What?

Default search now treats input as literal text (regex metacharacters are escaped).
Added “Use Regular Expression” toggle to opt in to regex behavior.
Persist the regex toggle per user via core/preferences.
Surface a friendly error for invalid regex input.
Added unit tests for regex escaping.

Why?

Editors reported this as a bug:

typing .’ and replacing with ." also replaces other characters.

This is because . was treated as “any character.” This is unexpected for non‑technical users.
Making literal matching the default aligns with non-technical user expectations while keeping regex available.

Closes #74

Open /wp-admin/post-new.php and add a few text blocks.
Open Search & Replace and try:
- Search: .’, Replace: ."
  - only the literal sequence should change.
- Enable “Use Regular Expression” and search for .
  - now matches any character.
  - Fun explicit functionality now: try using \d, \s \w to verify regex functionality
Edge cases/regression:
- Invalid regex (e.g. () shows the error message instead of replacing.
- Toggle persists per user across reloads.

Types of changes

Bug fix (non-breaking change)
New feature

Screenshots:

Copilot

Pull request overview

This PR addresses a user experience issue where non-technical users experienced unexpected text replacements due to regex metacharacters being interpreted as patterns rather than literal text. The fix makes literal text matching the default behavior while providing an opt-in "Use Regular Expression" toggle for power users who need regex functionality.

Changes:

Added escapeRegExp utility function to escape regex metacharacters for literal text matching
Introduced a "Use Regular Expression" toggle with user preference persistence via WordPress core/preferences
Added error handling and user-friendly error messages for invalid regex patterns

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
src/core/utils.tsx	Added `escapeRegExp` function to safely escape regex metacharacters for literal string matching
src/core/app.tsx	Integrated regex toggle, preference persistence, error handling, and conditional escaping of search input
tests/utils.test.tsx	Added unit tests for the new `escapeRegExp` function

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Copilot · 2026-01-28T16:04:55Z

tests/utils.test.tsx

+	it( 'escapeRegExp escapes regex metacharacters', () => {
+		const { escapeRegExp } = require( '../src/core/utils' );
+
+		const escaped = escapeRegExp( 'a.b+c*' );
+
+		expect( escaped ).toBe( 'a\\.b\\+c\\*' );
+	} );


The test for escapeRegExp only covers a subset of regex metacharacters (., +, *). The implementation at line 350 escapes all regex metacharacters including ^, $, {, }, (, ), |, [, ], and . Consider adding test cases that verify these additional characters are properly escaped. For example, test inputs like "test^$" should become "test\^\$" and "(test)" should become "$test$".

Copilot · 2026-01-28T16:04:55Z

tests/utils.test.tsx

+describe( 'escapeRegExp', () => {
+	beforeEach( () => {
+		jest.resetModules();
+	} );
+
+	it( 'escapeRegExp escapes regex metacharacters', () => {
+		const { escapeRegExp } = require( '../src/core/utils' );
+
+		const escaped = escapeRegExp( 'a.b+c*' );
+
+		expect( escaped ).toBe( 'a\\.b\\+c\\*' );
+	} );
+
+	it( 'escapeRegExp leaves plain text unchanged', () => {
+		const { escapeRegExp } = require( '../src/core/utils' );
+
+		const escaped = escapeRegExp( 'plain text' );
+
+		expect( escaped ).toBe( 'plain text' );
+	} );
+} );


The test coverage for escapeRegExp is missing an important edge case test that aligns with the guard clause in the implementation (line 346-348 in utils.tsx). Based on the pattern used in other tests in this file (e.g., getNumberToBase10 at lines 333-340), there should be a test case to verify that passing a non-string parameter returns an empty string.

Copilot · 2026-01-28T16:04:55Z

src/core/app.tsx

+	 * @return {void}
+	 */
+	const handleUseRegex = ( newValue: boolean ): void => {
+		setUseRegex( newValue );


When toggling the regex option (line 107-110), the error state is not cleared. If a user enters invalid regex syntax while in regex mode (which shows an error), then toggles regex off, the error message will persist even though the input would now be treated as literal text and is valid. Consider clearing the error state when toggling useRegex by adding setError('') in the handleUseRegex function.

Suggested change

setUseRegex( newValue );

setUseRegex( newValue );

setError( '' );

Copilot · 2026-01-28T16:04:56Z

tests/utils.test.tsx

+describe( 'escapeRegExp', () => {
+	beforeEach( () => {
+		jest.resetModules();
+	} );
+
+	it( 'escapeRegExp escapes regex metacharacters', () => {
+		const { escapeRegExp } = require( '../src/core/utils' );
+
+		const escaped = escapeRegExp( 'a.b+c*' );
+
+		expect( escaped ).toBe( 'a\\.b\\+c\\*' );
+	} );
+
+	it( 'escapeRegExp leaves plain text unchanged', () => {
+		const { escapeRegExp } = require( '../src/core/utils' );
+
+		const escaped = escapeRegExp( 'plain text' );
+
+		expect( escaped ).toBe( 'plain text' );
+	} );
+} );


Consider adding a test case for escapeRegExp with an empty string input to verify it returns an empty string, consistent with the behavior when a non-string is passed. This would complete the edge case coverage alongside the planned test for non-string inputs.

Copilot · 2026-01-28T16:04:56Z

src/core/app.tsx

+			setError(
+				__(
+					'Invalid regular expression.',
+					'search-replace-for-block-editor'
+				)


When an invalid regex error is shown and the user modifies the search input to correct it, the error will be cleared because the replace() function is called via the useEffect hook at line 121. However, if there's an error and the user clicks the "Replace" button (line 544), the error will persist if the regex is still invalid. This is correct behavior. However, consider providing more specific error information by including the actual regex error message from the caught exception, which would help users debug their regex patterns.

Suggested change

setError(

__(

'Invalid regular expression.',

'search-replace-for-block-editor'

)

const details =

err instanceof Error && err.message

? ' ' + err.message

: '';

setError(

__(

'Invalid regular expression.',

'search-replace-for-block-editor'

) + details

oekeur added 3 commits January 28, 2026 16:38

feat: add literal search escaping helper

0e5b54a

feat: add optional regex mode for search

2c5e784

chore: satisfy linting for regex toggle

c2d5d7d

Copilot AI review requested due to automatic review settings January 28, 2026 16:01

Copilot started reviewing on behalf of oekeur January 28, 2026 16:01 View session

Copilot AI reviewed Jan 28, 2026

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fix: make regex opt‑in for search/replace #75

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oekeur commented Jan 28, 2026 •

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	setUseRegex( newValue );
	setUseRegex( newValue );
	setError( '' );

fix: make regex opt‑in for search/replace #75

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oekeur commented Jan 28, 2026 •

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