feat: base (non-named) capture

Author: mdjastrzebski

src/__tests__/capture.test.tsx

@@ -0,0 +1,23 @@
+import { capture } from '../capture';
+import { buildPattern } from '../compiler';
+import { oneOrMore } from '../quantifiers/base';
+import { execRegex } from '../test-utils';
+
+test('"capture" base cases', () => {
+  expect(buildPattern(capture('a'))).toBe('(a)');
+  expect(buildPattern(capture('abc'))).toBe('(abc)');
+  expect(buildPattern(capture(oneOrMore('abc')))).toBe('((?:abc)+)');
+
+  // To be improved in optimized compiler
+  expect(buildPattern(oneOrMore(capture('abc')))).toBe('(?:(abc))+');
+});
+
+test('"capture" captures group', () => {
+  expect(execRegex('ab', [capture('b')])).toEqual(['b', 'b']);
+  expect(execRegex('ab', ['a', capture('b')])).toEqual(['ab', 'b']);
+  expect(execRegex('abc', ['a', capture('b'), capture('c')])).toEqual([
+    'abc',
+    'b',
+    'c',
+  ]);
+});

src/capture.ts

@@ -0,0 +1,12 @@
+import type { Capture, RegexElement } from './types';
+
+export function capture(...children: RegexElement[]): Capture {
+  return {
+    type: 'capture',
+    children,
+  };
+}
+
+export function compileCapture(compiledChildren: string): string {
+  return `(${compiledChildren})`;
+}

src/compiler.ts

@@ -4,6 +4,7 @@ import { compileCharacterClass } from './character-classes/compiler';
 import { baseQuantifiers, isBaseQuantifier } from './quantifiers/base';
 import { compileRepeat } from './quantifiers/repeat';
 import { escapeText } from './utils';
+import { compileCapture } from './capture';
 
 /**
  * Generate RegExp object for elements.
@@ -55,6 +56,11 @@ function compileSingle(element: RegexElement): string {
     return compiler(compiledChildren);
   }
 
+  if (element.type === 'capture') {
+    const compiledChildren = compileList(element.children);
+    return compileCapture(compiledChildren);
+  }
+
   // @ts-expect-error User passed incorrect type
   throw new Error(`Unknown elements type ${element.type}`);
 }

src/test-utils.ts

@@ -0,0 +1,12 @@
+import { buildRegex } from './compiler';
+import type { RegexElement } from './types';
+
+export function execRegex(text: string, elements: RegexElement[]) {
+  const regex = buildRegex(...elements);
+  return [...regex.exec(text)!];
+}
+
+export function execRegexFull(text: string, elements: RegexElement[]) {
+  const regex = buildRegex(...elements);
+  return regex.exec(text)!;
+}

src/types.ts

@@ -1,4 +1,9 @@
-export type RegexElement = string | ChoiceOf | CharacterClass | Quantifier;
+export type RegexElement =
+  | string
+  | CharacterClass
+  | ChoiceOf
+  | Quantifier
+  | Capture;
 
 export type Quantifier = One | OneOrMore | Optionally | ZeroOrMore | Repeat;
 
@@ -45,3 +50,9 @@ export type ZeroOrMore = {
   type: 'zeroOrMore';
   children: RegexElement[];
 };
+
+// Captures
+export type Capture = {
+  type: 'capture';
+  children: RegexElement[];
+};