Fix js declaration emit for exporting default which looks like namespace merge (#36482)

Fixes #35074

Author: sheetalkamat

src/compiler/checker.ts

@@ -3378,7 +3378,7 @@ namespace ts {
                         // `sym` may not have exports if this module declaration is backed by the symbol for a `const` that's being rewritten
                         // into a namespace - in such cases, it's best to just let the namespace appear empty (the const members couldn't have referred
                         // to one another anyway)
-                        if (result = callback(sym.exports || emptySymbols)) {
+                        if (result = callback(sym?.exports || emptySymbols)) {
                             return result;
                         }
                         break;
@@ -6134,7 +6134,7 @@ namespace ts {
                 }
 
                 function getDeclarationWithTypeAnnotation(symbol: Symbol) {
-                    return find(symbol.declarations, s => !!getEffectiveTypeAnnotationNode(s) && !!findAncestor(s, n => n === enclosingDeclaration));
+                    return symbol.declarations && find(symbol.declarations, s => !!getEffectiveTypeAnnotationNode(s) && !!findAncestor(s, n => n === enclosingDeclaration));
                 }
 
                 /**

tests/baselines/reference/jsDeclarationsWithDefaultAsNamespaceLikeMerge.js

@@ -0,0 +1,31 @@
+//// [tests/cases/compiler/jsDeclarationsWithDefaultAsNamespaceLikeMerge.ts] ////
+
+//// [helper.d.ts]
+type Computed = () => any;
+interface Mapper<R> {
+    <Key extends string>(map: Key[]): { [K in Key]: R };
+    <Map extends Record<string, string>>(map: Map): { [K in keyof Map]: R };
+}
+interface NamespacedMappers {
+    mapState: Mapper<Computed>;
+}
+export declare function createNamespacedHelpers(): NamespacedMappers;
+
+//// [index.js]
+import { createNamespacedHelpers } from './helper'
+const { mapState } = createNamespacedHelpers()
+export default {
+    computed: {
+        ...mapState(['panels'])
+    }
+}
+
+
+
+//// [index.d.ts]
+declare namespace _default {
+    export namespace computed {
+        export const panels: import("./helper").Computed;
+    }
+}
+export default _default;

tests/baselines/reference/jsDeclarationsWithDefaultAsNamespaceLikeMerge.symbols

@@ -0,0 +1,53 @@
+=== /helper.d.ts ===
+type Computed = () => any;
+>Computed : Symbol(Computed, Decl(helper.d.ts, 0, 0))
+
+interface Mapper<R> {
+>Mapper : Symbol(Mapper, Decl(helper.d.ts, 0, 26))
+>R : Symbol(R, Decl(helper.d.ts, 1, 17))
+
+    <Key extends string>(map: Key[]): { [K in Key]: R };
+>Key : Symbol(Key, Decl(helper.d.ts, 2, 5))
+>map : Symbol(map, Decl(helper.d.ts, 2, 25))
+>Key : Symbol(Key, Decl(helper.d.ts, 2, 5))
+>K : Symbol(K, Decl(helper.d.ts, 2, 41))
+>Key : Symbol(Key, Decl(helper.d.ts, 2, 5))
+>R : Symbol(R, Decl(helper.d.ts, 1, 17))
+
+    <Map extends Record<string, string>>(map: Map): { [K in keyof Map]: R };
+>Map : Symbol(Map, Decl(helper.d.ts, 3, 5))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+>map : Symbol(map, Decl(helper.d.ts, 3, 41))
+>Map : Symbol(Map, Decl(helper.d.ts, 3, 5))
+>K : Symbol(K, Decl(helper.d.ts, 3, 55))
+>Map : Symbol(Map, Decl(helper.d.ts, 3, 5))
+>R : Symbol(R, Decl(helper.d.ts, 1, 17))
+}
+interface NamespacedMappers {
+>NamespacedMappers : Symbol(NamespacedMappers, Decl(helper.d.ts, 4, 1))
+
+    mapState: Mapper<Computed>;
+>mapState : Symbol(NamespacedMappers.mapState, Decl(helper.d.ts, 5, 29))
+>Mapper : Symbol(Mapper, Decl(helper.d.ts, 0, 26))
+>Computed : Symbol(Computed, Decl(helper.d.ts, 0, 0))
+}
+export declare function createNamespacedHelpers(): NamespacedMappers;
+>createNamespacedHelpers : Symbol(createNamespacedHelpers, Decl(helper.d.ts, 7, 1))
+>NamespacedMappers : Symbol(NamespacedMappers, Decl(helper.d.ts, 4, 1))
+
+=== /index.js ===
+import { createNamespacedHelpers } from './helper'
+>createNamespacedHelpers : Symbol(createNamespacedHelpers, Decl(index.js, 0, 8))
+
+const { mapState } = createNamespacedHelpers()
+>mapState : Symbol(mapState, Decl(index.js, 1, 7))
+>createNamespacedHelpers : Symbol(createNamespacedHelpers, Decl(index.js, 0, 8))
+
+export default {
+    computed: {
+>computed : Symbol(computed, Decl(index.js, 2, 16))
+
+        ...mapState(['panels'])
+>mapState : Symbol(mapState, Decl(index.js, 1, 7))
+    }
+}

tests/baselines/reference/jsDeclarationsWithDefaultAsNamespaceLikeMerge.types

@@ -0,0 +1,41 @@
+=== /helper.d.ts ===
+type Computed = () => any;
+>Computed : Computed
+
+interface Mapper<R> {
+    <Key extends string>(map: Key[]): { [K in Key]: R };
+>map : Key[]
+
+    <Map extends Record<string, string>>(map: Map): { [K in keyof Map]: R };
+>map : Map
+}
+interface NamespacedMappers {
+    mapState: Mapper<Computed>;
+>mapState : Mapper<Computed>
+}
+export declare function createNamespacedHelpers(): NamespacedMappers;
+>createNamespacedHelpers : () => NamespacedMappers
+
+=== /index.js ===
+import { createNamespacedHelpers } from './helper'
+>createNamespacedHelpers : () => import("/helper").NamespacedMappers
+
+const { mapState } = createNamespacedHelpers()
+>mapState : import("/helper").Mapper<import("/helper").Computed>
+>createNamespacedHelpers() : import("/helper").NamespacedMappers
+>createNamespacedHelpers : () => import("/helper").NamespacedMappers
+
+export default {
+>{    computed: {        ...mapState(['panels'])    }} : { computed: { panels: import("/helper").Computed; }; }
+
+    computed: {
+>computed : { panels: import("/helper").Computed; }
+>{        ...mapState(['panels'])    } : { panels: import("/helper").Computed; }
+
+        ...mapState(['panels'])
+>mapState(['panels']) : { panels: import("/helper").Computed; }
+>mapState : import("/helper").Mapper<import("/helper").Computed>
+>['panels'] : "panels"[]
+>'panels' : "panels"
+    }
+}

tests/cases/compiler/jsDeclarationsWithDefaultAsNamespaceLikeMerge.ts

@@ -0,0 +1,23 @@
+// @declaration: true
+// @allowJs: true
+// @emitDeclarationOnly: true
+
+// @filename: /helper.d.ts
+type Computed = () => any;
+interface Mapper<R> {
+    <Key extends string>(map: Key[]): { [K in Key]: R };
+    <Map extends Record<string, string>>(map: Map): { [K in keyof Map]: R };
+}
+interface NamespacedMappers {
+    mapState: Mapper<Computed>;
+}
+export declare function createNamespacedHelpers(): NamespacedMappers;
+
+// @filename: /index.js
+import { createNamespacedHelpers } from './helper'
+const { mapState } = createNamespacedHelpers()
+export default {
+    computed: {
+        ...mapState(['panels'])
+    }
+}