run() fails when the venv path is too long

[wosc]

Currently, run() directly exec's the setuptools-generated entrypoint script, which in turn finds the correct python by including the full path to the {env_dir}/bin/python executable as a shebang line.

Shebang lines are limited to 127 characters, which is very easy to exceed with appenv, since the venv hash already takes up 64.

I propose to specify the python executable in appenv itself, instead of relying on the shebang line, like this:

diff --git a/batou b/batou
index 8f03df7..455def7 100755
--- a/batou
+++ b/batou
@@ -200,7 +200,10 @@ def run(argv, meta_args):
     env_dir = _prepare(meta_args)
     # Allow called programs to find out where the wrapper lives
     os.environ['APPENV_BASEDIR'] = meta_args.base
-    os.execv(os.path.join(env_dir, 'bin', meta_args.appname), argv)
+    interpreter = os.path.join(env_dir, 'bin', 'python')
+    entrypoint = os.path.join(env_dir, 'bin', meta_args.appname)
+    argv[0] = interpreter
+    argv.insert(1, entrypoint)
+    os.execv(interpreter, argv)
 

This works fine with batou, but argv[0] is not preserved (since at least under Debian we must set argv[0] to the venv/bin/python, otherwise the venv is not recognized and the spawned python runs with the system site-packages), so programs that are interested in that will have trouble. Not sure if that's something we have to worry about, though.

[ctheune]

Ok, so one thing I'm up for is to to actually reduce the venv hash to 8 characters, similar to git's short hash. This should still be reliable enough according to 'the internet' and 'stackoverflow'. I'm with that. It's not cryptographically secure but I don't think that matters here as we're basically using it for content addressing.

Did you try the most current version of appenv? I'm running batou on debian machines and think I have fixed the site-packages issue already through a pth hack... or does that fail for you?

[wosc]

This occurs with dc208ac, which is the current master, I'm afraid. Here's a reproduction recipe:

mkdir -p /tmp/appenv/work/workspace/somewhat-long-jenkins-job
cd /tmp/appenv/work/workspace/somewhat-long-jenkins-job
curl -o batou https://raw.githubusercontent.com/flyingcircusio/appenv/dc208ac9df334962b013001c60cd93fb88949c98/src/appenv.py
chmod +x batou
echo 'batou==2.0b11' > requirements.txt
./batou appenv-update-lockfile
./batou --help

which then yields

Creating venv ...
Ensuring pip ...
Installing batou ...
Traceback (most recent call last):
  File "./batou", line 312, in <module>
    main()
  File "./batou", line 308, in main
    meta_args.func(argv, meta_args)
  File "./batou", line 203, in run
    os.execv(os.path.join(env_dir, 'bin', meta_args.appname), argv)
OSError: [Errno 8] Exec format error