Improved detection of Clang versions (#10316)

Fixes #10191

* Add more regular expressions to detect clang versions that were
  not being picked up
* Add a test for parsing versions from the output of Clang (this
  does not run Clang, but rather uses example outputs from Clang)
* Separate Clang version parsing into its own method (to make it
  easier to test)

lib/spack/spack/compilers/clang.py

@@ -178,22 +178,33 @@ def default_version(cls, comp):
         if comp not in _version_cache:
             compiler = Executable(comp)
             output = compiler('--version', output=str, error=str)
-
-            ver = 'unknown'
-            match = re.search(r'^Apple LLVM version ([^ )]+)', output)
-            if match:
-                # Apple's LLVM compiler has its own versions, so suffix them.
-                ver = match.group(1) + '-apple'
-            else:
-                # Normal clang compiler versions are left as-is
-                match = re.search(r'clang version ([^ )]+)', output)
-                if match:
-                    ver = match.group(1)
-
-            _version_cache[comp] = ver
+            _version_cache[comp] = cls.detect_version_from_str(output)
 
         return _version_cache[comp]
 
+    @classmethod
+    def detect_version_from_str(cls, output):
+        """Returns the version that has been detected from the string
+        passed as input. If no detection is possible returns the
+        string 'unknown'.
+
+        Args:
+            output (str): string used to detect a compiler version
+        """
+        ver = 'unknown'
+        match = re.search(
+            # Apple's LLVM compiler has its own versions, so suffix them.
+            r'^Apple LLVM version ([^ )]+)|'
+            # Normal clang compiler versions are left as-is
+            r'clang version ([^ )]+)-svn[~.\w\d-]*|'
+            r'clang version ([^ )]+)',
+            output
+        )
+        if match:
+            suffix = '-apple' if match.lastindex == 1 else ''
+            ver = match.group(match.lastindex) + suffix
+        return ver
+
     @classmethod
     def fc_version(cls, fc):
         # We could map from gcc/gfortran version to clang version, but on macOS

lib/spack/spack/test/compilers.py

@@ -3,11 +3,15 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+import pytest
+
 from copy import copy
 from six import iteritems
 
 import spack.spec
+import spack.compiler
 import spack.compilers as compilers
+import spack.compilers.clang
 from spack.compiler import _get_versioned_tuple, Compiler
 
 
@@ -227,3 +231,23 @@ def test_xl_r_flags():
     unsupported_flag_test("cxx11_flag", "xl_r@13.0")
     supported_flag_test("cxx11_flag", "-qlanglvl=extended0x", "xl_r@13.1")
     supported_flag_test("pic_flag", "-qpic", "xl_r@1.0")
+
+
+@pytest.mark.regression('10191')
+@pytest.mark.parametrize('version_str,expected_version', [
+    # macOS clang
+    ('Apple LLVM version 7.0.2 (clang-700.1.81)\n'
+     'Target: x86_64-apple-darwin15.2.0\n'
+     'Thread model: posix\n', '7.0.2-apple'),
+    # Other platforms
+    ('clang version 6.0.1-svn334776-1~exp1~20181018152737.116 (branches/release_60)\n'  # noqa
+     'Target: x86_64-pc-linux-gnu\n'
+     'Thread model: posix\n'
+     'InstalledDir: /usr/bin\n', '6.0.1'),
+    ('clang version 3.1 (trunk 149096)\n'
+     'Target: x86_64-unknown-linux-gnu\n'
+     'Thread model: posix\n', '3.1'),
+])
+def test_clang_version_detection(version_str, expected_version):
+    version = spack.compilers.clang.Clang.detect_version_from_str(version_str)
+    assert version == expected_version