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Code Issues Releases Wiki Activity

Improve checkIfPRContentChanged (#22611)

Browse source 
The code for checking if a commit has caused a change in a PR is
extremely inefficient and affects the head repository instead of using a
temporary repository.

This PR therefore makes several significant improvements:

* A temporary repo like that used in merging.
* The diff code is then significant improved to use a three-way diff
instead of comparing diffs (possibly binary) line-by-line - in memory...

Ref #22578

Signed-off-by: Andrew Thornton <art27@cantab.net>
This commit is contained in:
zeripath 2023-01-28 15:54:40 +00:00 committed by GitHub
parent e9cd18b557
commit 78e6b21c1a
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
2 changed files with 59 additions and 51 deletions
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22
modules/util/io.go
View file

@ -4,6 +4,7 @@
package util
import (
"errors"
"io"
)
@ -17,3 +18,24 @@ func ReadAtMost(r io.Reader, buf []byte) (n int, err error) {
}
return n, err
}
// ErrNotEmpty is an error reported when there is a non-empty reader
var ErrNotEmpty = errors.New("not-empty")
// IsEmptyReader reads a reader and ensures it is empty
func IsEmptyReader(r io.Reader) (err error) {
var buf [1]byte
for {
n, err := r.Read(buf[:])
if err != nil {
if err == io.EOF {
return nil
}
return err
}
if n > 0 {
return ErrNotEmpty
}
}
}

88
services/pull/pull.go
View file

@ -4,14 +4,12 @@
package pull
import (
"bufio"
"bytes"
"context"
"fmt"
"io"
"os"
"regexp"
"strings"
"time"
"code.gitea.io/gitea/models"
"code.gitea.io/gitea/models/db"
@ -29,6 +27,7 @@ import (
repo_module "code.gitea.io/gitea/modules/repository"
"code.gitea.io/gitea/modules/setting"
"code.gitea.io/gitea/modules/sync"
"code.gitea.io/gitea/modules/util"
issue_service "code.gitea.io/gitea/services/issue"
)
@ -351,69 +350,56 @@ func AddTestPullRequestTask(doer *user_model.User, repoID int64, branch string,
// checkIfPRContentChanged checks if diff to target branch has changed by push
// A commit can be considered to leave the PR untouched if the patch/diff with its merge base is unchanged
func checkIfPRContentChanged(ctx context.Context, pr *issues_model.PullRequest, oldCommitID, newCommitID string) (hasChanged bool, err error) {
if err = pr.LoadHeadRepo(ctx); err != nil {
return false, fmt.Errorf("LoadHeadRepo: %w", err)
} else if pr.HeadRepo == nil {
// corrupt data assumed changed
return true, nil
tmpBasePath, err := createTemporaryRepo(ctx, pr)
if err != nil {
log.Error("CreateTemporaryRepo: %v", err)
return false, err
}
defer func() {
if err := repo_module.RemoveTemporaryPath(tmpBasePath); err != nil {
log.Error("checkIfPRContentChanged: RemoveTemporaryPath: %s", err)
}
}()
if err = pr.LoadBaseRepo(ctx); err != nil {
return false, fmt.Errorf("LoadBaseRepo: %w", err)
}
headGitRepo, err := git.OpenRepository(ctx, pr.HeadRepo.RepoPath())
tmpRepo, err := git.OpenRepository(ctx, tmpBasePath)
if err != nil {
return false, fmt.Errorf("OpenRepository: %w", err)
}
defer headGitRepo.Close()
defer tmpRepo.Close()
// Add a temporary remote.
tmpRemote := "checkIfPRContentChanged-" + fmt.Sprint(time.Now().UnixNano())
if err = headGitRepo.AddRemote(tmpRemote, pr.BaseRepo.RepoPath(), true); err != nil {
return false, fmt.Errorf("AddRemote: %s/%s-%s: %w", pr.HeadRepo.OwnerName, pr.HeadRepo.Name, tmpRemote, err)
}
defer func() {
if err := headGitRepo.RemoveRemote(tmpRemote); err != nil {
log.Error("checkIfPRContentChanged: RemoveRemote: %s/%s-%s: %v", pr.HeadRepo.OwnerName, pr.HeadRepo.Name, tmpRemote, err)
}
}()
// To synchronize repo and get a base ref
_, base, err := headGitRepo.GetMergeBase(tmpRemote, pr.BaseBranch, pr.HeadBranch)
// Find the merge-base
_, base, err := tmpRepo.GetMergeBase("", "base", "tracking")
if err != nil {
return false, fmt.Errorf("GetMergeBase: %w", err)
}
diffBefore := &bytes.Buffer{}
diffAfter := &bytes.Buffer{}
if err := headGitRepo.GetDiffFromMergeBase(base, oldCommitID, diffBefore); err != nil {
// If old commit not found, assume changed.
log.Debug("GetDiffFromMergeBase: %v", err)
return true, nil
}
if err := headGitRepo.GetDiffFromMergeBase(base, newCommitID, diffAfter); err != nil {
// New commit should be found
return false, fmt.Errorf("GetDiffFromMergeBase: %w", err)
cmd := git.NewCommand(ctx, "diff", "--name-only", "-z").AddDynamicArguments(newCommitID, oldCommitID, base)
stdoutReader, stdoutWriter, err := os.Pipe()
if err != nil {
return false, fmt.Errorf("unable to open pipe for to run diff: %w", err)
}
diffBeforeLines := bufio.NewScanner(diffBefore)
diffAfterLines := bufio.NewScanner(diffAfter)
for diffBeforeLines.Scan() && diffAfterLines.Scan() {
if strings.HasPrefix(diffBeforeLines.Text(), "index") && strings.HasPrefix(diffAfterLines.Text(), "index") {
// file hashes can change without the diff changing
continue
} else if strings.HasPrefix(diffBeforeLines.Text(), "@@") && strings.HasPrefix(diffAfterLines.Text(), "@@") {
// the location of the difference may change
continue
} else if !bytes.Equal(diffBeforeLines.Bytes(), diffAfterLines.Bytes()) {
if err := cmd.Run(&git.RunOpts{
Dir: tmpBasePath,
Stdout: stdoutWriter,
PipelineFunc: func(ctx context.Context, cancel context.CancelFunc) error {
_ = stdoutWriter.Close()
defer func() {
_ = stdoutReader.Close()
}()
return util.IsEmptyReader(stdoutReader)
},
}); err != nil {
if err == util.ErrNotEmpty {
return true, nil
}
}
if diffBeforeLines.Scan() || diffAfterLines.Scan() {
// Diffs not of equal length
return true, nil
log.Error("Unable to run diff on %s %s %s in tempRepo for PR[%d]%s/%s...%s/%s: Error: %v",
newCommitID, oldCommitID, base,
pr.ID, pr.BaseRepo.FullName(), pr.BaseBranch, pr.HeadRepo.FullName(), pr.HeadBranch,
err)
return false, fmt.Errorf("Unable to run git diff --name-only -z %s %s %s: %w", newCommitID, oldCommitID, base, err)
}
return false, nil