From b8a21886d2b309d72a692e007a5076fce5c14ff3 Mon Sep 17 00:00:00 2001
From: RunDevelopment <mitchi5000.ms@googlemail.com>
Date: Tue, 27 Jul 2021 13:00:49 +0200
Subject: [PATCH 1/2] Improve `no-dupe-disjunctions` by reordering alternatives

---
 lib/rules/no-dupe-disjunctions.ts       | 28 ++++++++++++++++++++++---
 tests/lib/rules/no-dupe-disjunctions.ts | 15 +++++++++++++
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/lib/rules/no-dupe-disjunctions.ts b/lib/rules/no-dupe-disjunctions.ts
index 7af0fd649..f829cc38d 100644
--- a/lib/rules/no-dupe-disjunctions.ts
+++ b/lib/rules/no-dupe-disjunctions.ts
@@ -29,6 +29,7 @@ import {
 } from "regexp-ast-analysis"
 import { RegExpParser } from "regexpp"
 import { UsageOfPattern } from "../utils/get-usage-of-pattern"
+import { canReorder } from "../utils/reorder-alternatives"
 
 type ParentNode = Group | CapturingGroup | Pattern | LookaroundAssertion
 
@@ -482,6 +483,7 @@ function* findPrefixDuplicationNfa(
  */
 function* findDuplicationNfa(
     alternatives: Alternative[],
+    context: RegExpContext,
     { hasNothingAfter, parser, ignoreOverlap }: Options,
 ): Iterable<Result> {
     const previous: [NFA, boolean, Alternative][] = []
@@ -524,9 +526,29 @@ function* findDuplicationNfa(
                     yield { type: "Subset", alternative, others }
                     break
 
-                case SubsetRelation.leftSupersetOfRight:
-                    yield { type: "Superset", alternative, others }
+                case SubsetRelation.leftSupersetOfRight: {
+                    const reorder = canReorder(
+                        [alternative, ...others],
+                        context,
+                        { ignoreCapturingGroups: true },
+                    )
+
+                    if (reorder) {
+                        // We are allowed to freely reorder the alternatives.
+                        // This means that we can reverse the order of our
+                        // alternatives to convert the superset into a subset.
+                        for (const other of others) {
+                            yield {
+                                type: "Subset",
+                                alternative: other,
+                                others: [alternative],
+                            }
+                        }
+                    } else {
+                        yield { type: "Superset", alternative, others }
+                    }
                     break
+                }
 
                 case SubsetRelation.none:
                 case SubsetRelation.unknown:
@@ -574,7 +596,7 @@ function* findDuplication(
 
     // NFA-based approach
     if (!options.noNfa) {
-        yield* findDuplicationNfa(alternatives, options)
+        yield* findDuplicationNfa(alternatives, context, options)
     }
 }
 
diff --git a/tests/lib/rules/no-dupe-disjunctions.ts b/tests/lib/rules/no-dupe-disjunctions.ts
index a0465b409..628bf89a0 100644
--- a/tests/lib/rules/no-dupe-disjunctions.ts
+++ b/tests/lib/rules/no-dupe-disjunctions.ts
@@ -365,6 +365,21 @@ tester.run("no-dupe-disjunctions", rule as any, {
         },
         {
             code: String(/\b(?:\d|foo|\w+)\b/),
+            errors: [
+                {
+                    message:
+                        "Unexpected useless alternative. This alternative is a strict subset of '\\w+' and can be removed.",
+                    column: 7,
+                },
+                {
+                    message:
+                        "Unexpected useless alternative. This alternative is a strict subset of '\\w+' and can be removed.",
+                    column: 10,
+                },
+            ],
+        },
+        {
+            code: String(/(?:\d|foo|\w+)a/),
             options: [{ report: "interesting" }],
             errors: [
                 "Unexpected superset. This alternative is a superset of '\\d|foo'. It might be possible to remove the other alternative(s).",

From e0e617496637a21ac3455e917f08fefb33b3a477 Mon Sep 17 00:00:00 2001
From: RunDevelopment <mitchi5000.ms@googlemail.com>
Date: Tue, 27 Jul 2021 13:04:45 +0200
Subject: [PATCH 2/2] Don't ignore capturing groups

---
 lib/rules/no-dupe-disjunctions.ts | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/rules/no-dupe-disjunctions.ts b/lib/rules/no-dupe-disjunctions.ts
index f829cc38d..93ccead8f 100644
--- a/lib/rules/no-dupe-disjunctions.ts
+++ b/lib/rules/no-dupe-disjunctions.ts
@@ -530,7 +530,6 @@ function* findDuplicationNfa(
                     const reorder = canReorder(
                         [alternative, ...others],
                         context,
-                        { ignoreCapturingGroups: true },
                     )
 
                     if (reorder) {