Add option to ignore class member implementations (#1174)

Author: Desuuuu

packages/knip/fixtures/class-members/index.ts

@@ -3,13 +3,12 @@ import { MyClass } from './members';
 import { AbstractClassGen, ExtendedClassGen } from './iterator-generator';
 import { AbstractClass, ExtendedClass } from './iterator';
 
-AbstractClassGen;
-ExtendedClassGen;
 AbstractClass;
-ExtendedClass;
 
 const instance = new MyClass();
 const some = new SomeClass();
+const instance2 = new ExtendedClass();
+const instance3: AbstractClassGen = new ExtendedClassGen();
 
 export class Parent {
   instance: MyClass;
@@ -27,3 +26,5 @@ instance.bUsedExternal;
 instance.cUsedExternal;
 instance.dUsedExternal();
 MyClass.eUsedExternal;
+instance2.implemented;
+instance3.implemented;

packages/knip/src/ProjectPrincipal.ts

@@ -78,6 +78,7 @@ export class ProjectPrincipal {
   };
 
   findReferences?: ts.LanguageService['findReferences'];
+  getImplementationAtPosition?: ts.LanguageService['getImplementationAtPosition'];
 
   constructor({
     compilerOptions,
@@ -260,14 +261,30 @@ export class ProjectPrincipal {
   }
 
   public findUnusedMembers(filePath: string, members: ExportMember[]) {
-    if (!this.findReferences) {
+    if (!this.findReferences || !this.getImplementationAtPosition) {
       const languageService = ts.createLanguageService(this.backend.languageServiceHost, ts.createDocumentRegistry());
       this.findReferences = timerify(languageService.findReferences);
+      this.getImplementationAtPosition = timerify(languageService.getImplementationAtPosition);
     }
 
     return members.filter(member => {
       if (member.jsDocTags.has(PUBLIC_TAG)) return false;
-      const referencedSymbols = this.findReferences?.(filePath, member.pos) ?? [];
+      const implementations =
+        this.getImplementationAtPosition?.(filePath, member.pos)?.filter(
+          impl => impl.fileName !== filePath || impl.textSpan.start !== member.pos
+        ) ?? [];
+
+      const referencedSymbols =
+        this.findReferences?.(filePath, member.pos)?.filter(
+          sym =>
+            !implementations.some(
+              impl =>
+                impl.fileName === sym.definition.fileName &&
+                impl.textSpan.start === sym.definition.textSpan.start &&
+                impl.textSpan.length === sym.definition.textSpan.length
+            )
+        ) ?? [];
+
       const refs = referencedSymbols.flatMap(refs => refs.references).filter(ref => !ref.isDefinition);
       return refs.length === 0;
     });
@@ -276,9 +293,10 @@ export class ProjectPrincipal {
   public hasExternalReferences(filePath: string, exportedItem: Export) {
     if (exportedItem.jsDocTags.has(PUBLIC_TAG)) return false;
 
-    if (!this.findReferences) {
+    if (!this.findReferences || !this.getImplementationAtPosition) {
       const languageService = ts.createLanguageService(this.backend.languageServiceHost, ts.createDocumentRegistry());
       this.findReferences = timerify(languageService.findReferences);
+      this.getImplementationAtPosition = timerify(languageService.getImplementationAtPosition);
     }
 
     const referencedSymbols = this.findReferences(filePath, exportedItem.pos);

packages/knip/test/class-members.test.ts

@@ -15,6 +15,7 @@ test('Find unused class members', async () => {
 
   assert.equal(Object.keys(issues.classMembers['members.ts']).length, 6);
   assert(issues.classMembers['iterator-generator.ts']['AbstractClassGen.unimplemented']);
+  assert(issues.classMembers['iterator.ts']['AbstractClass.implemented']);
   assert(issues.classMembers['members.ts']['MyClass.bUnusedPublic']);
   assert(issues.classMembers['members.ts']['MyClass.cUnusedProp']);
   assert(issues.classMembers['members.ts']['MyClass.dUnusedMember']);
@@ -24,7 +25,7 @@ test('Find unused class members', async () => {
 
   assert.deepEqual(counters, {
     ...baseCounters,
-    classMembers: 7,
+    classMembers: 8,
     processed: 5,
     total: 5,
   });
@@ -39,6 +40,7 @@ test('Find unused class members (isIncludeEntryExports)', async () => {
 
   assert.equal(Object.keys(issues.classMembers['members.ts']).length, 6);
   assert(issues.classMembers['iterator-generator.ts']['AbstractClassGen.unimplemented']);
+  assert(issues.classMembers['iterator.ts']['AbstractClass.implemented']);
   assert(issues.classMembers['index.ts']['Parent.unusedMemberInEntry']);
   assert(issues.classMembers['members.ts']['MyClass.bUnusedPublic']);
   assert(issues.classMembers['members.ts']['MyClass.cUnusedProp']);
@@ -49,7 +51,7 @@ test('Find unused class members (isIncludeEntryExports)', async () => {
 
   assert.deepEqual(counters, {
     ...baseCounters,
-    classMembers: 8,
+    classMembers: 9,
     processed: 5,
     total: 5,
   });