From e8aa737b09c0e5116565c92363d1aab806905dc6 Mon Sep 17 00:00:00 2001
From: Greg Becker <becker33@llnl.gov>
Date: Thu, 23 Jul 2020 10:54:25 -0700
Subject: [PATCH] util.executable.which: handle path separators like /bin/which
 (#17668)

* util.executable.which: handle path separators like /bin/which

Co-authored-by: Massimiliano Culpo <massimiliano.culpo@gmail.com>
---
 lib/spack/spack/test/util/executable.py | 30 +++++++++++++++++++++++++
 lib/spack/spack/util/executable.py      |  9 ++++++--
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/lib/spack/spack/test/util/executable.py b/lib/spack/spack/test/util/executable.py
index 5e8795f4bf..ae2859ea4b 100644
--- a/lib/spack/spack/test/util/executable.py
+++ b/lib/spack/spack/test/util/executable.py
@@ -40,6 +40,36 @@ def test_read_unicode(tmpdir, working_env):
         assert u'\xc3' == script(output=str).strip()
 
 
+def test_which_relative_path_with_slash(tmpdir, working_env):
+    tmpdir.ensure('exe')
+    path = str(tmpdir.join('exe'))
+    os.environ['PATH'] = ''
+
+    with tmpdir.as_cwd():
+        no_exe = ex.which('./exe')
+        assert no_exe is None
+
+        fs.set_executable(path)
+        exe = ex.which('./exe')
+        assert exe.path == path
+
+
+def test_which_with_slash_ignores_path(tmpdir, working_env):
+    tmpdir.ensure('exe')
+    tmpdir.ensure('bin{0}exe'.format(os.path.sep))
+
+    path = str(tmpdir.join('exe'))
+    wrong_path = str(tmpdir.join('bin', 'exe'))
+    os.environ['PATH'] = os.path.dirname(wrong_path)
+
+    fs.set_executable(path)
+    fs.set_executable(wrong_path)
+
+    with tmpdir.as_cwd():
+        exe = ex.which('./exe')
+        assert exe.path == path
+
+
 def test_which(tmpdir):
     os.environ["PATH"] = str(tmpdir)
     assert ex.which("spack-test-exe") is None
diff --git a/lib/spack/spack/util/executable.py b/lib/spack/spack/util/executable.py
index 28656b0a32..097da3337e 100644
--- a/lib/spack/spack/util/executable.py
+++ b/lib/spack/spack/util/executable.py
@@ -233,10 +233,15 @@ def which_string(*args, **kwargs):
         path = path.split(os.pathsep)
 
     for name in args:
-        for directory in path:
-            exe = os.path.join(directory, name)
+        if os.path.sep in name:
+            exe = os.path.abspath(name)
             if os.path.isfile(exe) and os.access(exe, os.X_OK):
                 return exe
+        else:
+            for directory in path:
+                exe = os.path.join(directory, name)
+                if os.path.isfile(exe) and os.access(exe, os.X_OK):
+                    return exe
 
     if required:
         raise CommandNotFoundError(