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Fix halfCommitter and WithTx #22366

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Jan 9, 2023
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27 changes: 22 additions & 5 deletions models/db/context.go
Original file line number Diff line number Diff line change
Expand Up @@ -98,19 +98,31 @@ type Committer interface {
// halfCommitter is a wrapper of Committer.
// It can be closed early, but can't be committed early, it is useful for reusing a transaction.
type halfCommitter struct {
Committer
committer Committer
committed bool
}

func (*halfCommitter) Commit() error {
// do nothing
func (c *halfCommitter) Commit() error {
c.committed = true
// should do nothing, and the parent committer will commit later
return nil
}

func (c *halfCommitter) Close() error {
if c.committed {
// it's "commit and close", should do nothing, and the parent committer will commit later
return nil
}

// it's "rollback and close", let the parent committer rollback right now
return c.committer.Close()
}

// TxContext represents a transaction Context,
// it will reuse the existing transaction in the parent context or create a new one.
func TxContext(parentCtx context.Context) (*Context, Committer, error) {
if sess, ok := inTransaction(parentCtx); ok {
return newContext(parentCtx, sess, true), &halfCommitter{Committer: sess}, nil
return newContext(parentCtx, sess, true), &halfCommitter{committer: sess}, nil
}

sess := x.NewSession()
Expand All @@ -126,7 +138,12 @@ func TxContext(parentCtx context.Context) (*Context, Committer, error) {
// this function will reuse it otherwise will create a new one and close it when finished.
func WithTx(parentCtx context.Context, f func(ctx context.Context) error) error {
if sess, ok := inTransaction(parentCtx); ok {
return f(newContext(parentCtx, sess, true))
err := f(newContext(parentCtx, sess, true))
if err != nil {
// rollback immediately, in case the caller ignores returned error and tries to commit the transaction.
_ = sess.Close()
}
return err
}
return txWithNoCheck(parentCtx, f)
}
Expand Down
102 changes: 102 additions & 0 deletions models/db/context_committer_test.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,102 @@
// Copyright 2022 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package db // it's not db_test, because this file is for testing the private type halfCommitter

import (
"fmt"
"testing"

"github.com/stretchr/testify/assert"
)

type MockCommitter struct {
wants []string
gots []string
}

func NewMockCommitter(wants ...string) *MockCommitter {
return &MockCommitter{
wants: wants,
}
}

func (c *MockCommitter) Commit() error {
c.gots = append(c.gots, "commit")
return nil
}

func (c *MockCommitter) Close() error {
c.gots = append(c.gots, "close")
return nil
}

func (c *MockCommitter) Assert(t *testing.T) {
assert.Equal(t, c.wants, c.gots, "want operations %v, but got %v", c.wants, c.gots)
}

func Test_halfCommitter(t *testing.T) {
/*
Do something like:

ctx, committer, err := db.TxContext(db.DefaultContext)
if err != nil {
return nil
}
defer committer.Close()

// ...

if err != nil {
return nil
}

// ...

return committer.Commit()
*/

testWithCommiter := func(committer Committer, f func(committer Committer) error) {
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if err := f(&halfCommitter{committer: committer}); err == nil {
committer.Commit()
}
committer.Close()
}

t.Run("commit and close", func(t *testing.T) {
mockCommitter := NewMockCommitter("commit", "close")

testWithCommiter(mockCommitter, func(committer Committer) error {
defer committer.Close()
return committer.Commit()
})

mockCommitter.Assert(t)
})

t.Run("rollback and close", func(t *testing.T) {
mockCommitter := NewMockCommitter("close", "close")

testWithCommiter(mockCommitter, func(committer Committer) error {
defer committer.Close()
if true {
return fmt.Errorf("error")
}
return committer.Commit()
})

mockCommitter.Assert(t)
})

t.Run("close and commit", func(t *testing.T) {
mockCommitter := NewMockCommitter("close", "close")

testWithCommiter(mockCommitter, func(committer Committer) error {
committer.Close()
committer.Commit()
return fmt.Errorf("error")
})

mockCommitter.Assert(t)
})
}