Closing pull request result in code 422- "Cannot change the base branch of a closed pull request"

[MarcinGinszt]

Steps to reproduce:

prs, _, _ := client.PullRequests.List(ctx, owner, repo, nil)
pull := prs[0]
pull.State = github.String("closed")
// pull.Base = nil  <- if this line is added, error does not appear
_, _, err := client.PullRequests.Edit(ctx, owner, repo, *pull.Number, pull)
require.NoError(t, err)

This code successfully closes the PR, but results in error:

received unexpected error:
PATCH https://api.github.com/repos/owner/repo/pulls/1: 422 Validation Failed [{Resource:PullRequest Field:base Code:invalid Message:Cannot change the base branch of a closed pull request.}]

Is that expected behaviour? Do I use the library correctly?

[gmlewis]

Actually, your code worked fine for me without modification, so I would check the settings in your repo if you have permissions to modify the PR in question.

Here's my working example (use of httpdebug is highly recommended):

package main

import (
	"context"
	"log"
	"os"

	dbg "github.com/gmlewis/go-httpdebug/httpdebug"
	"github.com/google/go-github/v68/github"
	"golang.org/x/oauth2"
)

const (
	owner = "gmlewis"
	repo  = "my-test-repo"
)

func main() {
	log.SetFlags(0)
	ts := oauth2.StaticTokenSource(
		&oauth2.Token{AccessToken: os.Getenv("GITHUB_SECRET")},
	)
	tc := oauth2.NewClient(oauth2.NoContext, ts)
	tp := dbg.New(dbg.WithTransport(tc.Transport))
	client := github.NewClient(tp.Client())
	ctx := context.Background()

	prs, _, err := client.PullRequests.List(ctx, owner, repo, nil)
	if err != nil {
		log.Fatal(err)
	}
	log.Printf("GML: Got %v PRs.", len(prs))

	pull := prs[0]
	pull.State = github.String("closed")
	// pull.Base = nil // <- if this line is added, error does not appear
	if _, _, err := client.PullRequests.Edit(ctx, owner, repo, *pull.Number, pull); err != nil {
		log.Fatal(err)
	}

	log.Printf("Done.")
}

Here's the run:

go run main.go
curl -X GET \
  https://api.github.com/repos/gmlewis/my-test-repo/pulls \
  -H 'Accept: application/vnd.github.v3+json' \
  -H 'User-Agent: go-github/v68.0.0' \
  -H 'X-Github-Api-Version: 2022-11-28'
GML: Got 1 PRs.
curl -X PATCH \
  https://api.github.com/repos/gmlewis/my-test-repo/pulls/10 \
  -H 'Accept: application/vnd.github.v3+json' \
  -H 'Content-Type: application/json' \
  -H 'User-Agent: go-github/v68.0.0' \
  -H 'X-Github-Api-Version: 2022-11-28' \
  -d '{"title":"test PR","body":"Description","state":"closed"}
'
Done.

The PR in question was successfully closed: gmlewis/my-test-repo#10

[gmlewis]

Your error message sounds funny though:

Cannot change the base branch of a closed pull request.

sounds like you were trying to close an already-closed pull request... I'm not sure how that happened.
But the code above looks fine to me.

[gmlewis]

Closing due to inactivity.