Merge pull request #614 from jflan-dd/jflan/pipe-overfill

Drain stdout pipe while command is running

Author: f-meloni

CHANGELOG.md

@@ -13,6 +13,8 @@
 
 ## Master
 
+- Drain stdout while shell commands are running to prevent execution from locking up if there's too much output [@jflan-dd][] - [#614](https://github.com/danger/swift/pull/614)
+
 ## 3.20.0
 - Remove deprecated `lint` function with `lintAllFiles` flag [@417-72KI][] - [#622](https://github.com/danger/swift/pull/622)
 - Updated Swift 6 build process: Danger files moved to .build/debug/Modules, and SwiftFormat module map conflict resolved by adjusting the Swift import search path. [@abhi-m-simformsolutons][] -[#626](https://github.com/danger/swift/pull/626)

Sources/DangerShellExecutor/ShellExecutor.swift

@@ -61,9 +61,11 @@ public struct ShellExecutor: ShellExecuting {
         let pipe = Pipe()
         task.standardOutput = pipe
         task.launch()
-        task.waitUntilExit()
 
         let data = pipe.fileHandleForReading.readDataToEndOfFile()
+
+        task.waitUntilExit()
+
         return String(data: data, encoding: .utf8)!.trimmingCharacters(in: .whitespacesAndNewlines)
     }
 
@@ -83,19 +85,22 @@ public struct ShellExecutor: ShellExecuting {
         let stderr = Pipe()
         task.standardError = stderr
         task.launch()
-        task.waitUntilExit()
 
         // Pull out the STDOUT as a string because we'll need that regardless
         let stdoutData = stdout.fileHandleForReading.readDataToEndOfFile()
         let stdoutString = String(data: stdoutData, encoding: .utf8)!
 
+        // Read from STDERR to ensure the `Pipe` does not fill up
+        let stderrData = stderr.fileHandleForReading.readDataToEndOfFile()
+
+        task.waitUntilExit()
+
         // 0 is no problems in unix land
         if task.terminationStatus == 0 {
             return stdoutString.trimmingCharacters(in: .whitespacesAndNewlines)
         }
 
         // OK, so it failed, raise a new error with all the useful metadata
-        let stderrData = stderr.fileHandleForReading.readDataToEndOfFile()
         let stderrString = String(data: stderrData, encoding: .utf8)!
 
         throw SpawnError.commandFailed(command: command,