Fix path parameter serialization with flat params structure

[Copilot]

Path parameters were incorrectly serialized when using paramsStructure: 'flat' in the SDK plugin. A call like getServer({ id: '123' }) would generate URL /servers/id,123 instead of /servers/123.

Root Cause

The code generator was passing field configs directly to buildClientParams:

const params = buildClientParams([parameters], [
  { in: 'path', key: 'id' }
]);

This caused buildClientParams to treat the entire parameters object as a positional argument instead of iterating over its properties.

Changes

Modified packages/openapi-ts/src/plugins/@hey-api/sdk/shared/operation.ts:

• Added conditional check for plugin.config.paramsStructure === 'flat'
• When flat, wrap field configs in an args array to signal object iteration mode
• Preserve existing behavior for grouped params

Generated code now correctly wraps fields:

const params = buildClientParams([parameters], [
  {
    args: [
      { in: 'path', key: 'id' }
    ]
  }
]);

This tells buildClientParams to iterate over parameters properties and extract individual values, producing correct path parameter serialization.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Path parameter incorrectly serialized as /servers/id, instead of /servers/ on paramsStructure flat</issue_title>
<issue_description>### Description

Hi, I encountered an issue when calling (with paramsStructure flat) a generated GET method.
The request path is incorrectly serialized as:
/servers/id,1335279038599663729

But it should be:
/servers/1335279038599663729

This looks like the {id} placeholder is not replaced properly and the value is appended with a comma.

Let me know if you need any further details or if I can provide additional logs or config.

Reproducible example or configuration

import { defineConfig } from '@hey-api/openapi-ts';

export default defineConfig({
	input: './scripts/openapi-spec.json',
	output: { path: './src/api/client', importFileExtension: '.js' },
	plugins: [
		'@hey-api/schemas',
		{
			name: '@hey-api/typescript',
			topType: "any",
			enums: {
				case: 'preserve',
				enabled: true,
				mode: 'typescript'
			}
		},
		{
			name: '@hey-api/sdk',
			asClass: true,
			responseStyle: 'data',
			paramsStructure: 'flat',
			classNameBuilder: (name) => `${name}Service`
		}
	]
});

OpenAPI specification (optional)

    "/servers/{id}": {
      "get": {
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "schema": {
              "type": "string"
            },
            "required": true
          }
        ],
        "responses": {
          "200": {
            "description": "Ok",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/IServer"
                }
              }
            }
          }
        },
        "tags": [
          "Servers"
        ],
        "security": [],
        "operationId": "GetServer"
      },

System information (optional)

@hey-api/openapi-ts: 0.87.5</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Path parameter incorrectly serialized as /servers/id,<id> instead of /servers/<id> on paramsStructure flat #2984

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Project	Deployment	Preview	Comments	Updated (UTC)
hey-api-docs	Ready	Preview	Comment	Nov 15, 2025 2:58am

[fiftyy]

Generated code now correctly wraps fields:

const params = buildClientParams([parameters], [
  {
    args: [
      { in: 'path', key: 'id' }
    ]
  }
]);

This tells buildClientParams to iterate over parameters properties and extract individual values, producing correct path parameter serialization.

Tested it by replacing my function with this. Works good.

[fiftyy]

Can we trigger a test build with pkg-pr-new bot? @mrlubos