Fix #2917

Author: Gerrit0

CHANGELOG.md

@@ -4,6 +4,10 @@ title: Changelog
 
 ## Unreleased
 
+### Bug Fixes
+
+- API: `toString` on types containing index signatures now behave correctly, #2917.
+
 ## v0.28.1 (2025-03-20)
 
 ### Features

src/lib/models/types.ts

@@ -1098,19 +1098,19 @@ export class ReflectionType extends Type {
 
     protected override getTypeString() {
         const parts: string[] = [];
-        const sigs = this.declaration.getAllSignatures();
+        const sigs = this.declaration.getNonIndexSignatures();
         for (const sig of sigs) {
             parts.push(sigStr(sig, ": "));
         }
 
-        if (this.declaration.children) {
-            for (const p of this.declaration.children) {
-                parts.push(`${p.name}${propertySep(p)} ${typeStr(p.type)}`);
-            }
-            return `{ ${parts.join("; ")} }`;
+        for (const p of this.declaration.children || []) {
+            parts.push(`${p.name}${propertySep(p)} ${typeStr(p.type)}`);
+        }
+        for (const s of this.declaration.indexSignatures || []) {
+            parts.push(sigStr(s, ": ", "[]"));
         }
 
-        if (sigs.length === 1) {
+        if (sigs.length === 1 && parts.length === 1) {
             return sigStr(sigs[0], " => ");
         }
 
@@ -1486,11 +1486,11 @@ function typeStr(type: Type | undefined) {
     return type?.toString() ?? "any";
 }
 
-function sigStr(sig: SignatureReflection, sep: string) {
+function sigStr(sig: SignatureReflection, sep: string, brackets = "()") {
     const params = joinArray(
         sig.parameters,
         ", ",
         (p) => `${p.name}${propertySep(p)} ${typeStr(p.type)}`,
     );
-    return `(${params})${sep}${typeStr(sig.type)}`;
+    return `${brackets[0]}${params}${brackets[1]}${sep}${typeStr(sig.type)}`;
 }

src/test/converter2/issues/gh2917.ts

@@ -0,0 +1,10 @@
+export interface Foo {
+    data: {
+        [key: string]: any;
+    };
+    mixed: {
+        (): string;
+        a: string;
+        [key: string]: any;
+    };
+}

src/test/issues.c2.test.ts

@@ -2042,4 +2042,12 @@ describe("Issue Tests", () => {
         const exp = query(project, "export=");
         equal(exp.type?.toString(), "never[]");
     });
+
+    it("#2917 stringifies index signatures", () => {
+        const project = convert();
+        const data = query(project, "Foo.data");
+        equal(data.type?.toString(), "{ [key: string]: any }");
+        const mixed = query(project, "Foo.mixed");
+        equal(mixed.type?.toString(), "{ (): string; a: string; [key: string]: any }");
+    });
 });