From 938ef7bd4ff653602cee8e479b9b7bec22b08e59 Mon Sep 17 00:00:00 2001
From: Xavier Deguillard <xavierd@fb.com>
Date: Thu, 13 Aug 2020 01:22:48 -0700
Subject: [PATCH] flush stdout before starting a command while interactive

Summary:
Now that the subprocess output is no longer piped, we can see a weird situation
where the command being run is displayed after the compilation step:
  + cd /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/build/eden && \
  [1/13] rust_job_pool
      Finished release [optimized] target(s) in 0.75s
  [12/13] Install the project...
  -- Install configuration: "RelWithDebInfo"
  -- Installing: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/bin/edenfs
  -- Set runtime path of "/data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/bin/edenfs" to ""
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/bin/edenfsctl
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/lib/libbackingstore_rs.a
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/lib/libbackingstore.a
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/include/eden/scm/lib/backingstore/c_api/HgNativeBackingStore.h
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/include/eden/scm/lib/backingstore/c_api/RustBackingStore.h
  + /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/cmake-Ncng4tsJb6gdOu40ggy14-YtgNQD43 (https://github.com/facebook/proxygen/commit/f2db269ce032393667c272071dcbf6a70e60ff44)k5ev0n-FXq99I/bin/cmake \
  +      --build \
  +      /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/build/eden \
  +      --target \
  +      install \
  +      --config \
  +      Release \
  +      -j \
  +      24

This is a bit awkward. Flushing stdout's buffer allows for the ordering to be
correct.

Reviewed By: wez

Differential Revision: D23079405

fbshipit-source-id: e2bf25b098d6ab4a788a5ec07deb635a42cae18c
---
 build/fbcode_builder/getdeps/runcmd.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/build/fbcode_builder/getdeps/runcmd.py b/build/fbcode_builder/getdeps/runcmd.py
index b2cd56606..de306e369 100644
--- a/build/fbcode_builder/getdeps/runcmd.py
+++ b/build/fbcode_builder/getdeps/runcmd.py
@@ -98,6 +98,7 @@ def _run_cmd(cmd, env, cwd, allow_fail, log_fn):
     isinteractive = os.isatty(sys.stdout.fileno())
     if isinteractive:
         stdout = None
+        sys.stdout.buffer.flush()
     else:
         stdout = subprocess.PIPE