Fix input stream piping in Forker (Issue #882)#2855
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dorodb-web22 wants to merge 3 commits intoscalacenter:mainfrom
Open
Fix input stream piping in Forker (Issue #882)#2855dorodb-web22 wants to merge 3 commits intoscalacenter:mainfrom
dorodb-web22 wants to merge 3 commits intoscalacenter:mainfrom
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tgodzik
reviewed
Jan 22, 2026
| opts.env.toMap, | ||
| writeToStdIn = outputStream => { | ||
| val mainCancellable = goobleInput(outputStream) | ||
| val thread = new Thread { |
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Are you able to add some tests? I can confirm that this is fixing the issues at hand
Author
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I've added the tests as requested.
The test cases verify that the blocking reader thread approach fixes the stdin readline issue, covering:
- Input forwarding without data loss
- No indefinite waiting when reading from stdin
- Compatibility with forker-realib patterns
4)Standard I/O patterns work correctly
Could you approve the workflow run so CI can execute the tests? Thanks!
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Fixes #882.
Problem
Reading input from
stdin(e.g. usingreadInt) was flaky. The issue was that we were usingInputStream.available()to poll for data. This method isn't reliable; it often returns 0 even when data is waiting, causing the process to drop input or wait indefinitely.Solution
I've replaced the polling mechanism with a standard blocking reader thread.
gobbleInputloop that relied onavailable().read()call. As soon as any bytes appear, they are immediately piped to the forked process's standard input.This ensures input is forwarded immediately on all platforms.
Verification
Forker.scalachanges follow standard I/O patterns.