feat: add support for ES2025 duplicate named capturing groups

src/ast.ts

@@ -428,10 +428,21 @@ export interface Character extends NodeBase {
  * The backreference.
  * E.g. `\1`, `\k<name>`
  */
-export interface Backreference extends NodeBase {
+export type Backreference = AmbiguousBackreference | UnambiguousBackreference
+interface BaseBackreference extends NodeBase {
     type: "Backreference"
     parent: Alternative | Quantifier
     ref: number | string
+    ambiguous: boolean
+    resolved: CapturingGroup | CapturingGroup[]
+}
+export interface AmbiguousBackreference extends BaseBackreference {
+    ref: string
+    ambiguous: true
+    resolved: CapturingGroup[]
+}
+export interface UnambiguousBackreference extends BaseBackreference {
+    ambiguous: false
     resolved: CapturingGroup
 }
 

src/ecma-versions.ts

@@ -10,4 +10,5 @@ export type EcmaVersion =
     | 2022
     | 2023
     | 2024
-export const latestEcmaVersion = 2024
+    | 2025
+export const latestEcmaVersion = 2025

src/group-specifiers.ts

@@ -0,0 +1,167 @@
+/**
+ * Holds information for all GroupSpecifiers included in the pattern.
+ */
+export interface GroupSpecifiers {
+    /**
+     * @returns true if there are no GroupSpecifiers included in the pattern.
+     */
+    isEmpty: () => boolean
+    clear: () => void
+    /**
+     * Called when visiting the Disjunction.
+     * For ES2025, manage nesting with new Disjunction scopes.
+     */
+    enterDisjunction: () => void
+    /**
+     * Called when visiting the Alternative.
+     * For ES2025, manage nesting with new Alternative scopes.
+     */
+    enterAlternative: (index: number) => void
+    /**
+     * Called when leaving the Disjunction.
+     */
+    leaveDisjunction: () => unknown
+    /**
+     * Checks whether the given group name is within the pattern.
+     */
+    hasInPattern: (name: string) => boolean
+    /**
+     * Checks whether the given group name is within the current scope.
+     */
+    hasInScope: (name: string) => boolean
+    /**
+     * Adds the given group name to the current scope.
+     */
+    addToScope: (name: string) => void
+}
+
+export class GroupSpecifiersAsES2018 implements GroupSpecifiers {
+    private readonly groupName = new Set<string>()
+
+    public clear(): void {
+        this.groupName.clear()
+    }
+
+    public isEmpty(): boolean {
+        return !this.groupName.size
+    }
+
+    public hasInPattern(name: string): boolean {
+        return this.groupName.has(name)
+    }
+
+    public hasInScope(name: string): boolean {
+        return this.hasInPattern(name)
+    }
+
+    public addToScope(name: string): void {
+        this.groupName.add(name)
+    }
+
+    // eslint-disable-next-line class-methods-use-this
+    public enterDisjunction(): void {
+        // Prior to ES2025, it does not manage disjunction scopes.
+    }
+
+    // eslint-disable-next-line class-methods-use-this
+    public enterAlternative(): void {
+        // Prior to ES2025, it does not manage alternative scopes.
+    }
+
+    // eslint-disable-next-line class-methods-use-this
+    public leaveDisjunction(): void {
+        // Prior to ES2025, it does not manage disjunction scopes.
+    }
+}
+
+/**
+ * Track disjunction structure to determine whether a duplicate
+ * capture group name is allowed because it is in a separate branch.
+ */
+class BranchID {
+    public readonly parent: BranchID | null
+    private readonly base: BranchID
+    public constructor(parent: BranchID | null, base: BranchID | null) {
+        // Parent disjunction branch
+        this.parent = parent
+        // Identifies this set of sibling branches
+        this.base = base ?? this
+    }
+
+    /**
+     * A branch is separate from another branch if they or any of
+     * their parents are siblings in a given disjunction
+     */
+    public separatedFrom(other: BranchID): boolean {
+        if (this.base === other.base && this !== other) {
+            return true
+        }
+        if (other.parent && this.separatedFrom(other.parent)) {
+            return true
+        }
+        return this.parent?.separatedFrom(other) ?? false
+    }
+
+    public child() {
+        return new BranchID(this, null)
+    }
+
+    public sibling() {
+        return new BranchID(this.parent, this.base)
+    }
+}
+
+export class GroupSpecifiersAsES2025 implements GroupSpecifiers {
+    private branchID = new BranchID(null, null)
+    private readonly groupNames = new Map<string, BranchID[]>()
+
+    public clear(): void {
+        this.branchID = new BranchID(null, null)
+        this.groupNames.clear()
+    }
+
+    public isEmpty(): boolean {
+        return !this.groupNames.size
+    }
+
+    public enterDisjunction(): void {
+        this.branchID = this.branchID.child()
+    }
+
+    public enterAlternative(index: number): void {
+        if (index === 0) {
+            return
+        }
+        this.branchID = this.branchID.sibling()
+    }
+
+    public leaveDisjunction(): void {
+        this.branchID = this.branchID.parent!
+    }
+
+    public hasInPattern(name: string): boolean {
+        return this.groupNames.has(name)
+    }
+
+    public hasInScope(name: string): boolean {
+        const branches = this.groupNames.get(name)
+        if (!branches) {
+            return false
+        }
+        for (const branch of branches) {
+            if (!branch.separatedFrom(this.branchID)) {
+                return true
+            }
+        }
+        return false
+    }
+
+    public addToScope(name: string): void {
+        const branches = this.groupNames.get(name)
+        if (branches) {
+            branches.push(this.branchID)
+            return
+        }
+        this.groupNames.set(name, [this.branchID])
+    }
+}

src/parser.ts

@@ -148,12 +148,21 @@ class RegExpParserState {
 
         for (const reference of this._backreferences) {
             const ref = reference.ref
-            const group =
+            const groups =
                 typeof ref === "number"
-                    ? this._capturingGroups[ref - 1]
-                    : this._capturingGroups.find((g) => g.name === ref)!
-            reference.resolved = group
-            group.references.push(reference)
+                    ? [this._capturingGroups[ref - 1]]
+                    : this._capturingGroups.filter((g) => g.name === ref)
+            if (groups.length === 1) {
+                const group = groups[0]
+                reference.ambiguous = false
+                reference.resolved = group
+            } else {
+                reference.ambiguous = true
+                reference.resolved = groups
+            }
+            for (const group of groups) {
+                group.references.push(reference)
+            }
         }
     }
 
@@ -480,6 +489,7 @@ class RegExpParserState {
             end,
             raw: this.source.slice(start, end),
             ref,
+            ambiguous: false,
             resolved: DUMMY_CAPTURING_GROUP,
         }
         parent.elements.push(node)
@@ -747,14 +757,15 @@ export namespace RegExpParser {
         strict?: boolean
 
         /**
-         * ECMAScript version. Default is `2024`.
+         * ECMAScript version. Default is `2025`.
          * - `2015` added `u` and `y` flags.
          * - `2018` added `s` flag, Named Capturing Group, Lookbehind Assertion,
          *   and Unicode Property Escape.
          * - `2019`, `2020`, and `2021` added more valid Unicode Property Escapes.
          * - `2022` added `d` flag.
          * - `2023` added more valid Unicode Property Escapes.
          * - `2024` added `v` flag.
+         * - `2025` added duplicate named capturing groups.
          */
         ecmaVersion?: EcmaVersion
     }

src/validator.ts

@@ -1,5 +1,10 @@
 import type { EcmaVersion } from "./ecma-versions"
 import { latestEcmaVersion } from "./ecma-versions"
+import type { GroupSpecifiers } from "./group-specifiers"
+import {
+    GroupSpecifiersAsES2018,
+    GroupSpecifiersAsES2025,
+} from "./group-specifiers"
 import { Reader } from "./reader"
 import { newRegExpSyntaxError } from "./regexp-syntax-error"
 import {
@@ -231,14 +236,15 @@ export namespace RegExpValidator {
         strict?: boolean
 
         /**
-         * ECMAScript version. Default is `2024`.
+         * ECMAScript version. Default is `2025`.
          * - `2015` added `u` and `y` flags.
          * - `2018` added `s` flag, Named Capturing Group, Lookbehind Assertion,
          *   and Unicode Property Escape.
          * - `2019`, `2020`, and `2021` added more valid Unicode Property Escapes.
          * - `2022` added `d` flag.
          * - `2023` added more valid Unicode Property Escapes.
          * - `2024` added `v` flag.
+         * - `2025` added duplicate named capturing groups.
          */
         ecmaVersion?: EcmaVersion
 
@@ -631,7 +637,7 @@ export class RegExpValidator {
 
     private _numCapturingParens = 0
 
-    private _groupNames = new Set<string>()
+    private _groupSpecifiers: GroupSpecifiers
 
     private _backreferenceNames = new Set<string>()
 
@@ -643,6 +649,10 @@ export class RegExpValidator {
      */
     public constructor(options?: RegExpValidator.Options) {
         this._options = options ?? {}
+        this._groupSpecifiers =
+            this.ecmaVersion >= 2025
+                ? new GroupSpecifiersAsES2025()
+                : new GroupSpecifiersAsES2018()
     }
 
     /**
@@ -763,7 +773,7 @@ export class RegExpValidator {
         if (
             !this._nFlag &&
             this.ecmaVersion >= 2018 &&
-            this._groupNames.size > 0
+            !this._groupSpecifiers.isEmpty()
         ) {
             this._nFlag = true
             this.rewind(start)
@@ -1301,7 +1311,7 @@ export class RegExpValidator {
     private consumePattern(): void {
         const start = this.index
         this._numCapturingParens = this.countCapturingParens()
-        this._groupNames.clear()
+        this._groupSpecifiers.clear()
         this._backreferenceNames.clear()
 
         this.onPatternEnter(start)
@@ -1322,7 +1332,7 @@ export class RegExpValidator {
             this.raise(`Unexpected character '${c}'`)
         }
         for (const name of this._backreferenceNames) {
-            if (!this._groupNames.has(name)) {
+            if (!this._groupSpecifiers.hasInPattern(name)) {
                 this.raise("Invalid named capture referenced")
             }
         }
@@ -1378,6 +1388,7 @@ export class RegExpValidator {
         const start = this.index
         let i = 0
 
+        this._groupSpecifiers.enterDisjunction()
         this.onDisjunctionEnter(start)
         do {
             this.consumeAlternative(i++)
@@ -1390,6 +1401,7 @@ export class RegExpValidator {
             this.raise("Lone quantifier brackets")
         }
         this.onDisjunctionLeave(start, this.index)
+        this._groupSpecifiers.leaveDisjunction()
     }
 
     /**
@@ -1403,6 +1415,7 @@ export class RegExpValidator {
     private consumeAlternative(i: number): void {
         const start = this.index
 
+        this._groupSpecifiers.enterAlternative(i)
         this.onAlternativeEnter(start, i)
         while (this.currentCodePoint !== -1 && this.consumeTerm()) {
             // do nothing.
@@ -1846,8 +1859,8 @@ export class RegExpValidator {
     private consumeGroupSpecifier(): boolean {
         if (this.eat(QUESTION_MARK)) {
             if (this.eatGroupName()) {
-                if (!this._groupNames.has(this._lastStrValue)) {
-                    this._groupNames.add(this._lastStrValue)
+                if (!this._groupSpecifiers.hasInScope(this._lastStrValue)) {
+                    this._groupSpecifiers.addToScope(this._lastStrValue)
                     return true
                 }
                 this.raise("Duplicate capture group name")

test/fixtures/parser/literal/basic-valid-2015-u.json

@@ -1690,6 +1690,7 @@
                   "end": 6,
                   "raw": "\\1",
                   "ref": 1,
+                  "ambiguous": false,
                   "resolved": "♻️../0"
                 }
               ]
@@ -1741,6 +1742,7 @@
                   "end": 3,
                   "raw": "\\1",
                   "ref": 1,
+                  "ambiguous": false,
                   "resolved": "♻️../1"
                 },
                 {
@@ -2104,6 +2106,7 @@
                   "end": 34,
                   "raw": "\\10",
                   "ref": 10,
+                  "ambiguous": false,
                   "resolved": "♻️../9"
                 }
               ]
@@ -2465,6 +2468,7 @@
                   "end": 37,
                   "raw": "\\11",
                   "ref": 11,
+                  "ambiguous": false,
                   "resolved": "♻️../10"
                 }
               ]