feat: parameters is optional when every parameter is optional

Closes openapi-ts#1334

Author: duncanbeevers

packages/openapi-typescript/src/transform/components-object.ts

@@ -48,27 +48,36 @@ export default function transformComponentsObject(components: ComponentsObject,
 
   // parameters
   if (components.parameters) {
-    output.push(indent("parameters: {", indentLv));
+    const parameters: string[] = [];
     indentLv++;
+
+    let isEveryParameterOptional = true;
+
     for (const [name, parameterObject] of getEntries(components.parameters, ctx.alphabetize, ctx.excludeDeprecated)) {
       const c = getSchemaObjectComment(parameterObject, indentLv);
-      if (c) output.push(indent(c, indentLv));
+      if (c) parameters.push(indent(c, indentLv));
       let key = escObjKey(name);
       if (ctx.immutableTypes) key = tsReadonly(key);
       if ("$ref" in parameterObject) {
-        output.push(indent(`${key}: ${transformSchemaObject(parameterObject, { path: `#/components/parameters/${name}`, ctx })};`, indentLv));
+        parameters.push(indent(`${key}: ${transformSchemaObject(parameterObject, { path: `#/components/parameters/${name}`, ctx })};`, indentLv));
+        isEveryParameterOptional = false;
       } else {
         if (parameterObject.in !== "path" && !parameterObject.required) {
           key = tsOptionalProperty(key);
+        } else {
+          isEveryParameterOptional = false;
         }
         const parameterType = transformParameterObject(parameterObject, {
           path: `#/components/parameters/${name}`,
           ctx: { ...ctx, indentLv },
         });
-        output.push(indent(`${key}: ${parameterType};`, indentLv));
+        parameters.push(indent(`${key}: ${parameterType};`, indentLv));
       }
     }
     indentLv--;
+    const parametersKey = isEveryParameterOptional ? tsOptionalProperty("parameters") : "parameters";
+    output.push(indent(`${parametersKey}: {`, indentLv));
+    output.push(...parameters);
     output.push(indent("};", indentLv));
   } else {
     output.push(indent("parameters: never;", indentLv));

packages/openapi-typescript/test/components-object.test.ts

@@ -293,7 +293,7 @@ describe("Components Object", () => {
     expect(generated).toBe(`{
   schemas: never;
   responses: never;
-  parameters: {
+  parameters?: {
     myParam?: string;
     myParam2?: string;
   };