From 81ea5049afefcf75d20a1304ef7674f3bd803add Mon Sep 17 00:00:00 2001
From: tydeu <tydeu@hatpress.net>
Date: Wed, 1 Jun 2022 18:09:39 -0400
Subject: [PATCH] feat: caption process stdout and stderr

closes leanprover/lake#54
---
 Lake/Build/Actions.lean | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/Lake/Build/Actions.lean b/Lake/Build/Actions.lean
index c029dd3ce6..4bcd2fdaa3 100644
--- a/Lake/Build/Actions.lean
+++ b/Lake/Build/Actions.lean
@@ -19,11 +19,15 @@ def proc (args : IO.Process.SpawnArgs) : BuildM PUnit := do
     | some cwd => s!"{cmdStr}    # in directory {cwd}"
     | none     => cmdStr
   let out ← IO.Process.output args
-  unless out.stdout.isEmpty do
-    logInfo out.stdout
-  unless out.stderr.isEmpty do
-    logError out.stderr
-  if out.exitCode != 0 then
+  let logOutputWith (log : String → BuildM PUnit) := do
+    unless out.stdout.isEmpty do
+      log s!"stdout:\n{out.stdout}"
+    unless out.stderr.isEmpty do
+      log s!"stderr:\n{out.stderr}"
+  if out.exitCode = 0 then
+    logOutputWith logInfo
+  else
+    logOutputWith logError
     logError s!"external command {args.cmd} exited with status {out.exitCode}"
     failure