fix(eslint-plugin): [unified-signatures] type comparison and exported nodes (#839)

Author: uniqueiniquity

.gitignore

@@ -60,3 +60,6 @@ jspm_packages/
 .DS_Store
 .idea
 dist
+
+# Editor-specific metadata folders
+.vs

packages/eslint-plugin/src/rules/unified-signatures.ts

@@ -35,6 +35,9 @@ type ScopeNode =
   | TSESTree.TSTypeLiteral;
 
 type OverloadNode = MethodDefinition | SignatureDefinition;
+type ContainingNode =
+  | TSESTree.ExportNamedDeclaration
+  | TSESTree.ExportDefaultDeclaration;
 
 type SignatureDefinition =
   | TSESTree.FunctionExpression
@@ -424,7 +427,8 @@ export default util.createRule({
         a === b ||
         (a !== undefined &&
           b !== undefined &&
-          a.typeAnnotation.type === b.typeAnnotation.type)
+          sourceCode.getText(a.typeAnnotation) ===
+            sourceCode.getText(b.typeAnnotation))
       );
     }
 
@@ -495,9 +499,16 @@ export default util.createRule({
       currentScope = scopes.pop()!;
     }
 
-    function addOverload(signature: OverloadNode, key?: string): void {
+    function addOverload(
+      signature: OverloadNode,
+      key?: string,
+      containingNode?: ContainingNode,
+    ): void {
       key = key || getOverloadKey(signature);
-      if (currentScope && signature.parent === currentScope.parent && key) {
+      if (
+        currentScope &&
+        (containingNode || signature).parent === currentScope.parent
+      ) {
         const overloads = currentScope.overloads.get(key);
         if (overloads !== undefined) {
           overloads.push(signature);
@@ -521,11 +532,10 @@ export default util.createRule({
         createScope(node.body, node.typeParameters);
       },
       TSTypeLiteral: createScope,
+
       // collect overloads
       TSDeclareFunction(node): void {
-        if (node.id && !node.body) {
-          addOverload(node, node.id.name);
-        }
+        addOverload(node, node.id.name, getExportingNode(node));
       },
       TSCallSignatureDeclaration: addOverload,
       TSConstructSignatureDeclaration: addOverload,
@@ -540,6 +550,7 @@ export default util.createRule({
           addOverload(node);
         }
       },
+
       // validate scopes
       'Program:exit': checkScope,
       'TSModuleBlock:exit': checkScope,
@@ -550,7 +561,20 @@ export default util.createRule({
   },
 });
 
-function getOverloadKey(node: OverloadNode): string | undefined {
+function getExportingNode(
+  node: TSESTree.TSDeclareFunction,
+):
+  | TSESTree.ExportNamedDeclaration
+  | TSESTree.ExportDefaultDeclaration
+  | undefined {
+  return node.parent &&
+    (node.parent.type === AST_NODE_TYPES.ExportNamedDeclaration ||
+      node.parent.type === AST_NODE_TYPES.ExportDefaultDeclaration)
+    ? node.parent
+    : undefined;
+}
+
+function getOverloadKey(node: OverloadNode): string {
   const info = getOverloadInfo(node);
 
   return (

packages/eslint-plugin/tests/rules/unified-signatures.test.ts

@@ -105,6 +105,30 @@ interface I {
 function f<T extends number>(x: T[]): void;
 function f<T extends string>(x: T): void;
  `,
+    // Same name, different scopes
+    `
+declare function foo(n: number): number;
+
+declare module "hello" {
+  function foo(n: number, s: string): number;
+}
+`,
+    // children of block not checked to match TSLint
+    `
+{
+    function block(): number;
+    function block(n: number): number;
+    function block(n?: number): number {
+      return 3;
+    }
+}
+`,
+    `
+export interface Foo {
+  bar(baz: string): number[];
+  bar(): string[];
+}
+`,
   ],
   invalid: [
     {
@@ -591,5 +615,39 @@ class Foo {
         },
       ],
     },
+    {
+      code: `
+export function foo(line: number): number;
+export function foo(line: number, character?: number): number;
+`,
+      errors: [
+        {
+          messageId: 'omittingSingleParameter',
+          data: {
+            failureStringStart:
+              'These overloads can be combined into one signature',
+          },
+          line: 3,
+          column: 35,
+        },
+      ],
+    },
+    {
+      code: `
+declare function foo(line: number): number;
+export function foo(line: number, character?: number): number;
+`,
+      errors: [
+        {
+          messageId: 'omittingSingleParameter',
+          data: {
+            failureStringStart:
+              'These overloads can be combined into one signature',
+          },
+          line: 3,
+          column: 35,
+        },
+      ],
+    },
   ],
 });

packages/typescript-estree/src/ts-estree/ts-estree.ts

@@ -1040,6 +1040,7 @@ export interface TSConstructSignatureDeclaration extends FunctionSignatureBase {
 }
 
 export interface TSDeclareFunction extends FunctionDeclarationBase {
+  id: Identifier;
   type: AST_NODE_TYPES.TSDeclareFunction;
 }