Fix container logs -n truncating the oldest line past a read chunk#1968
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OrtegaMatias wants to merge 1 commit into
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Fix container logs -n truncating the oldest line past a read chunk#1968OrtegaMatias wants to merge 1 commit into
container logs -n truncating the oldest line past a read chunk#1968OrtegaMatias wants to merge 1 commit into
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`container logs -n N` read the log file backwards in 1024-byte chunks and stopped at `lines.count < n`. When the last N lines spanned more than one chunk, the oldest line in the buffer was a fragment truncated at the chunk boundary and was returned as-is — e.g. a single log line longer than 1024 bytes with `-n 1` returned only its last 1024 bytes. Extract the backward-read into a testable `lastLines(fh:n:)` and read one line past N (`<= n`) so the partial leading line is dropped by `suffix(n)`, or stop at the start of the file. The full-log path is unchanged.
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Type of Change
Motivation and Context
container logs -n Ntruncated the oldest returned line whenever the last N log lines spanned more than one 1024-byte backward-read chunk. The clearest case: a single log line longer than 1024 bytes with-n 1returns only its last 1024 bytes — the beginning of the line is cut off. The full-log path (container logswithout-n) is unaffected.Fixes #1967.
Description
ContainerLogs.tailreads the log file backwards in 1024-byte chunks and stopped atlines.count < n. When a read landed on exactly N non-empty segments whose first was a fragment (buffer starting mid-line,offset > 0), that fragment was returned as the oldest line.lastLines(fh:n:) -> [String].lines.count < ntolines.count <= n, so it always reads one line past N (or to the start of the file). The extra, possibly-partial leading line is then dropped bysuffix(n), guaranteeing the oldest returned line is complete.No behavior change for the common case (last N lines within one chunk); the full-log path is untouched.
Testing
Added
Tests/ContainerCommandsTests/ContainerLogsTailTests.swiftcovering:-n 1),-n 2),ngreater than the number of lines.Transparency note: I was unable to run the in-repo test suite locally — this machine only has an Xcode 27 beta toolchain (which fails building a transitive dependency under strict concurrency) and the Command Line Tools, which lack the test frameworks. I verified the fix logic in isolation (old logic truncates the oldest line; new logic returns it in full for all four cases above) and confirmed the change compiles as part of the
ContainerCommandstarget. CI runs the added tests.