fix: prevent double-close in partsReader by advancing index after Close#60
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In partsReader.Read, when Close() returns an error after EOF, r.index was not incremented — causing the same already-closed reader to be closed again by the outer Close() method. In partsReader.WriteTo, none of the three error-return paths incremented r.index after closing the reader, leading to the same double-close bug. Fix: increment r.index before returning in both error paths, so that a closed reader is always marked as consumed regardless of Close/io.Copy outcome. Closes #57 Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Pull request overview
This PR addresses a resource-lifecycle bug in pkg/iobuf’s composite partsReader where failures during per-part Close() could leave r.index unchanged, causing later Close() calls to double-close the same underlying reader (issue #57). It also adds unit tests covering the regression scenarios.
Changes:
- Advance
r.indexwhenRead()encountersClose()errors afterio.EOF, preventing subsequent double-close. - Advance
r.indexonWriteTo()error paths for the same double-close prevention. - Add 3 unit tests to cover the fixed scenarios.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
pkg/iobuf/part_reader.go |
Advances internal index on specific error paths in Read/WriteTo to avoid double-closing parts. |
pkg/iobuf/part_reader_test.go |
Adds regression tests for index advancement on Close()/copy errors and successful WriteTo() behavior. |
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Comment on lines
+68
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| @@ -68,6 +69,7 @@ func (r *partsReader) WriteTo(w io.Writer) (n int64, err error) { | |||
| nn, err = io.Copy(w, reader) | |||
| n += nn | |||
| if err != nil { | |||
| r.index++ | |||
Comment on lines
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| // eofCloseErrReader returns data + io.EOF in a single Read, and returns the given error on Close. | ||
| type eofCloseErrReader struct { | ||
| data string | ||
| readOnce bool | ||
| closeErr error | ||
| closeCount *int | ||
| } | ||
|
|
||
| func (r *eofCloseErrReader) Read(p []byte) (int, error) { | ||
| if r.readOnce { | ||
| return 0, io.EOF | ||
| } | ||
| r.readOnce = true | ||
| n := copy(p, r.data) | ||
| if n == 0 { | ||
| return 0, io.EOF | ||
| } | ||
| return n, io.EOF | ||
| } |
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Summary
partsReader.Read中Close()返回错误时r.index未递增，导致后续Close()重复关闭已关闭的 readerpartsReader.WriteTo中所有错误退出路径均未递增r.index的同源问题根因
见 #57
Test plan
TestPartsReader_Read_CloseErrorAdvancesIndex— 验证 Read 中 Close 失败后索引前进TestPartsReader_WriteTo_ErrorAdvancesIndex— 验证 WriteTo 中 io.Copy 错误后索引前进TestPartsReader_WriteTo_AllSuccess— 验证正常 WriteTo 全路径pkg/iobuf测试通过Closes #57
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