fix: preserve empty array as request body in stripEmptySlots by Copilot · Pull Request #3451 · hey-api/openapi-ts

Copilot · 2026-02-25T21:11:58Z

Identify root cause: stripEmptySlots in params.ts treats empty arrays as empty objects and removes them
Fix stripEmptySlots to skip array values (add !Array.isArray(value) check)
Add test case for empty array body
Build and verify fix - all 12 unit tests pass
Update 242 test snapshots (pnpm test:update)
Regenerate all examples (pnpm examples:generate)

Original prompt

This section details on the original issue you should resolve

<issue_title>Body of a json empty array should send to server</issue_title>
<issue_description>### Description

We have an API endpoint where you can update the value with an empty array. However, in the params.gen.ts the function stripEmptySlots removes the array from the body params since it is empty. Here is the params at the start of the function. After the function, the only one remaining is the path.

I would think you could strip all parameters if empty for everything but the body?

Reproducible example or configuration

  await createClient({
    input: openApi,
    output: outpath,
    parser: {
      transforms: {
        propertiesRequiredByDefault: true
      }
    },
    plugins: [
      {
        name: '@hey-api/sdk',
        responseStyle: 'data',
        paramsStructure: 'flat'
      }
    ]
  })

The key call that is failing:

updateItemListForStateUpdates({ connectionId: "xxxxxx", body: [] })

As stated above, since the body is an empty array, the stripEmptySlots removes the body from the params group and then no body is include as part of the POST which causes the issue.

OpenAPI specification (optional)

{
    "openapi": "3.0.1",
    "info": {
        "title": "openHAB REST API",
        "contact": {
            "name": "openHAB",
            "url": "https://www.openhab.org/docs/"
        },
        "version": "8"
    },
    "servers": [
        {
            "url": "/rest"
        }
    ],
    "paths": {
        "/events/states/{connectionId}": {
            "post": {
                "tags": [
                    "events"
                ],
                "summary": "Changes the list of items a SSE connection will receive state updates to.",
                "operationId": "updateItemListForStateUpdates",
                "parameters": [
                    {
                        "name": "connectionId",
                        "in": "path",
                        "required": true,
                        "schema": {
                            "type": "string"
                        }
                    }
                ],
                "requestBody": {
                    "description": "items",
                    "content": {
                        "application/json": {
                            "schema": {
                                "uniqueItems": true,
                                "type": "array",
                                "items": {
                                    "type": "string"
                                }
                            }
                        }
                    }
                },
                "responses": {
                    "200": {
                        "description": "OK"
                    },
                    "404": {
                        "description": "Unknown connectionId"
                    }
                }
            }
        }
    }
}
```</issue_description>

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

<comments>
<comment_new><author>@mrlubos</author><body>
@jsjames Can you add spec and config to reproduce?</body></comment_new>
<comment_new><author>@mrlubos</author><body>
@jsjames Drop it in this issue. Minimal spec is enough, don't need the whole document</body></comment_new>
<comment_new><author>@mrlubos</author><body>
@jsjames which version are you using? this looks quite outdated. Can you confirm the problem persists with the latest release?</body></comment_new>
</comments>

Fixes Body of a json empty array should send to server #3340

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changeset-bot · 2026-02-25T21:12:05Z

🦋 Changeset detected

Latest commit: 1518fda

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Co-authored-by: mrlubos <12529395+mrlubos@users.noreply.github.com>

mrlubos · 2026-02-25T21:20:03Z

@copilot you're going to have to make sure you updated snapshots with pnpm test:update and examples with pnpm examples:generate

Co-authored-by: mrlubos <12529395+mrlubos@users.noreply.github.com>

Copilot · 2026-02-25T21:27:09Z

@copilot you're going to have to make sure you updated snapshots with pnpm test:update and examples with pnpm examples:generate

Done in b1f91cd — ran pnpm test:update (242 snapshots updated) and pnpm examples:generate (all 14 examples regenerated) to propagate the !Array.isArray(value) change to all generated params.gen.ts files.

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Updated the changeset to include '@hey-api/openapi-ts' and modified the fix description.

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codecov · 2026-02-25T21:34:03Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.13%. Comparing base (320c30a) to head (1518fda).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3451   +/-   ##
=======================================
  Coverage   40.13%   40.13%           
=======================================
  Files         478      478           
  Lines       17479    17479           
  Branches     5295     5295           
=======================================
  Hits         7016     7016           
  Misses       8418     8418           
  Partials     2045     2045

Flag	Coverage Δ
unittests	`40.13% <100.00%> (ø)`

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commit: 1518fda

Initial plan

f505c8c

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fix: preserve empty array body in stripEmptySlots

86ee54a

Co-authored-by: mrlubos <12529395+mrlubos@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix issue with sending empty array to server~~ fix: preserve empty array as request body in stripEmptySlots Feb 25, 2026

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chore: update snapshots and examples with Array.isArray fix

b1f91cd

Co-authored-by: mrlubos <12529395+mrlubos@users.noreply.github.com>

Copilot finished work on behalf of mrlubos February 25, 2026 21:27

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Update changeset and fix description

1518fda

Updated the changeset to include '@hey-api/openapi-ts' and modified the fix description.

mrlubos approved these changes Feb 25, 2026

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dosubot bot added size:M This PR changes 30-99 lines, ignoring generated files. bug 🔥 Broken or incorrect behavior. labels Feb 25, 2026

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mrlubos merged commit cf74327 into main Feb 25, 2026
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mrlubos deleted the copilot/fix-empty-array-sending branch February 25, 2026 21:37

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