Fixed false positives for hasIndices in regexp/no-unused-capturing-group (#676)

Author: ota-meshi

.changeset/thick-numbers-fry.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-regexp": patch
+---
+
+Fixed false positives for hasIndices in `regexp/no-unused-capturing-group`

lib/utils/extract-capturing-group-references.ts

@@ -641,12 +641,12 @@ function* iterateForRegExpMatchArrayReference(
             for (const namedRef of ref.extractPropertyReferences()) {
                 yield getNamedArrayRef(namedRef)
             }
+        } else if (ref.name === "indices") {
+            for (const indicesRef of ref.extractPropertyReferences()) {
+                yield* iterateForRegExpIndicesArrayReference(indicesRef)
+            }
         } else {
-            if (
-                ref.name === "input" ||
-                ref.name === "index" ||
-                ref.name === "indices"
-            ) {
+            if (ref.name === "input" || ref.name === "index") {
                 return
             }
             yield getIndexArrayRef(ref)
@@ -660,6 +660,27 @@ function* iterateForRegExpMatchArrayReference(
     }
 }
 
+/** Iterate the capturing group references for RegExpIndicesArray reference. */
+function* iterateForRegExpIndicesArrayReference(
+    ref: PropertyReference,
+): Iterable<CapturingGroupReference> {
+    if (hasNameRef(ref)) {
+        if (ref.name === "groups") {
+            for (const namedRef of ref.extractPropertyReferences()) {
+                yield getNamedArrayRef(namedRef)
+            }
+        } else {
+            yield getIndexArrayRef(ref)
+        }
+    } else {
+        yield {
+            type: "UnknownRef",
+            kind: "array",
+            prop: ref,
+        }
+    }
+}
+
 /** Iterate the capturing group references for Array method of String.prototype.matchAll(). */
 function* iterateForArrayMethodOfStringMatchAll(
     node: CallExpression,

tests/lib/rules/no-unused-capturing-group.ts

@@ -152,6 +152,16 @@ tester.run("no-unused-capturing-group", rule as any, {
         const text = 'Lorem ipsum dolor sit amet'
         const replaced = text.replace(/([\q{Lorem|ipsum}])/vg, '**$1**')
         `,
+        // hasIndices
+        String.raw`const re = /(foo)/d
+        console.log(re.exec('foo').indices[1])
+        `,
+        String.raw`const re = /(?<f>foo)/d
+        console.log(re.exec('foo').indices.groups.f)
+        `,
+        String.raw`const re = /(foo)/d
+        console.log(re.exec('foo').indices[unknown])
+        `,
     ],
     invalid: [
         {
@@ -546,5 +556,26 @@ tester.run("no-unused-capturing-group", rule as any, {
             options: [{ fixable: true }],
             errors: ["Capturing group number 1 is defined but never used."],
         },
+        // hasIndices
+        {
+            code: String.raw`const re = /(foo)/d
+            console.log(re.exec('foo').indices[2])
+            `,
+            output: String.raw`const re = /(?:foo)/d
+            console.log(re.exec('foo').indices[2])
+            `,
+            options: [{ fixable: true }],
+            errors: ["Capturing group number 1 is defined but never used."],
+        },
+        {
+            code: String.raw`const re = /(?<f>foo)/d
+            console.log(re.exec('foo').indices.groups.x)
+            `,
+            output: String.raw`const re = /(?:foo)/d
+            console.log(re.exec('foo').indices.groups.x)
+            `,
+            options: [{ fixable: true }],
+            errors: ["Capturing group 'f' is defined but never used."],
+        },
     ],
 })