build: minor refactoring

---
type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:
  - task: lint_filenames
    status: passed
  - task: lint_editorconfig
    status: passed
  - task: lint_markdown
    status: na
  - task: lint_package_json
    status: na
  - task: lint_repl_help
    status: na
  - task: lint_javascript_src
    status: passed
  - task: lint_javascript_cli
    status: na
  - task: lint_javascript_examples
    status: na
  - task: lint_javascript_tests
    status: na
  - task: lint_javascript_benchmarks
    status: na
  - task: lint_python
    status: na
  - task: lint_r
    status: na
  - task: lint_c_src
    status: na
  - task: lint_c_examples
    status: na
  - task: lint_c_benchmarks
    status: na
  - task: lint_c_tests_fixtures
    status: na
  - task: lint_shell
    status: na
  - task: lint_typescript_declarations
    status: na
  - task: lint_typescript_tests
    status: na
  - task: lint_license_headers
    status: passed
---

Author: Planeshifter

lib/node_modules/@stdlib/_tools/eslint/rules/tsdoc-doctest/lib/main.js

@@ -16,6 +16,8 @@
 * limitations under the License.
 */
 
+/* eslint-disable max-len, max-lines */
+
 'use strict';
 
 // MODULES //
@@ -43,14 +45,51 @@ var debug = logger( 'tsdoc-doctest' );
 var RE_TSDOC = /\/\*\*[\s\S]+?\*\//g;
 var RE_EXAMPLE = /@example\s*([\s\S]*?)(?=\n\s*@\w|\*\/|$)/g;
 var RE_NEWLINE = /\r?\n/g;
-var RE_ANNOTATION = /(?:\n|^)(?:var|let|const)? ?([a-zA-Z0-9._]+) ?=[^;]*?;\n\/\/ ?(returns|([A-Za-z][A-Za-z_0-9]*)? ?=>|throws) {0,1}([\s\S]*?)(\n|$)/g;
+var RE_ANNOTATION = /(?:\n|^)(?:var|let|const)? ?([a-zA-Z0-9._]+) ?=[^;]*;\n\/\/ ?(returns|([A-Za-z][A-Za-z_0-9]*)? ?=>|throws) ?([\s\S]*?)(\n|$)/g;
 var RE_CONSOLE = /console\.(?:dir|error|log)/;
 var RE_COMMENT_PREFIX = /^\s*\*\s?/gm;
+var RE_SPECIAL_CHARS = /[.*+?^${}()|[\]\\]/g;
+var regexCache = {};
+var lineCountCache = {};
 var rule;
 
 
 // FUNCTIONS //
 
+/**
+* Escapes special regex characters in a string.
+*
+* @private
+* @param {string} str - string to escape
+* @returns {string} escaped string
+*/
+function escapeRegex( str ) {
+	return str.replace( RE_SPECIAL_CHARS, '\\$&' );
+}
+
+/**
+* Gets or creates a cached regex for finding return annotations.
+*
+* @private
+* @param {string} annotationType - type of annotation (returns, throws, etc.)
+* @param {string} value - expected value
+* @returns {RegExp} compiled regular expression
+*/
+function getAnnotationRegex( annotationType, value ) {
+	var escapedValue;
+	var pattern;
+	var key;
+
+	escapedValue = escapeRegex( value );
+	key = [ annotationType, escapedValue ].join( '::' );
+
+	if ( !regexCache[ key ] ) {
+		pattern = '// ' + annotationType + '\\s+' + escapedValue;
+		regexCache[ key ] = new RegExp( pattern );
+	}
+	return regexCache[ key ];
+}
+
 /**
 * Counts the number of lines in the given string.
 *
@@ -59,7 +98,15 @@ var rule;
 * @returns {number} number of lines
 */
 function countLines( str ) {
-	return ( str.match( RE_NEWLINE ) || '' ).length;
+	var matches;
+
+	// Use cached result if available
+	if ( lineCountCache[ str ] ) {
+		return lineCountCache[ str ];
+	}
+	matches = str.match( RE_NEWLINE );
+	lineCountCache[ str ] = ( matches ) ? matches.length : 0;
+	return lineCountCache[ str ];
 }
 
 /**
@@ -78,7 +125,7 @@ function findName( scope, expected ) {
 		key = keys[ i ];
 		if (
 			!contains( SCOPE_DEFAULTS, key ) &&
-			!compareValues( scope[ key ], expected )
+			compareValues( scope[ key ], expected ) === null
 		) {
 			return key;
 		}
@@ -175,7 +222,7 @@ function processExampleCode( code, commentIdx, comments, scope, report, opts, so
 			commentStartIdx = sourceCode.text.indexOf( comments[ commentIdx ] );
 
 			// Find the annotation in the original comment
-			returnAnnotationPattern = new RegExp( '// ' + arr[ 2 ] + '\\s+' + arr[ 4 ].replace( /[.*+?^${}()|[\]\\]/g, '\\$&' ) );
+			returnAnnotationPattern = getAnnotationRegex( arr[ 2 ], arr[ 4 ] );
 			annotationMatch = comments[ commentIdx ].match( returnAnnotationPattern );
 
 			if ( !annotationMatch ) {
@@ -281,9 +328,6 @@ function processExampleCode( code, commentIdx, comments, scope, report, opts, so
 	}
 }
 
-
-// MAIN //
-
 /**
 * Rule for validating that return annotations in TypeScript declaration examples match the actual output.
 *
@@ -357,6 +401,10 @@ function main( context ) {
 		var i;
 		var j;
 
+		// Clear caches to prevent memory leaks
+		regexCache = {};
+		lineCountCache = {};
+
 		// Resolve implementation path relative to TypeScript declaration file path:
 		implementationPath = options.implementationPath || '../../lib';
 		implPath = resolveImplementationPath( filename, implementationPath );