improve version()

CHANGES

@@ -5,7 +5,7 @@ Changelog
 Version 0.7.2 (in development)
 ------------------------------
 
-Add backend.version() function.
+Add grapviz.version() function.
 
 
 Version 0.7.1

docs/api.rst

@@ -50,7 +50,6 @@ documented above.
 
 .. autofunction:: graphviz.render
 .. autofunction:: graphviz.pipe
-.. autofunction:: graphviz.version
 .. autofunction:: graphviz.view
 
 
@@ -65,3 +64,5 @@ Other
 
 .. autodata:: graphviz.ExecutableNotFound
    :annotation:
+
+.. autofunction:: graphviz.version

graphviz/backend.py

@@ -172,10 +172,11 @@ def version():
     """Return the version number tuple from the stderr output of ``dot -V``.
 
     Returns:
-        Two/three int version tuple or None (if the output cannot be parsed).
+        Two or three int version tuple.
     Raises:
         graphviz.ExecutableNotFound: If the Graphviz executable is not found.
         subprocess.CalledProcessError: If the exit status is non-zero.
+        RuntimmeError: If the output cannot be parsed into a version number.
     """
     args = ['dot', '-V']
     try:
@@ -189,7 +190,9 @@ def version():
 
     info = outs.decode('ascii')
     ma = re.search(r'graphviz version (\d+\.\d+(?:\.\d+)?) ', info)
-    return tuple(int(d) for d in ma.group(1).split('.')) if ma is not None else None
+    if ma is None:
+        raise RuntimeError
+    return tuple(int(d) for d in ma.group(1).split('.'))
 
 
 def view(filepath):

tests/test_backend.py

@@ -135,6 +135,14 @@ def test_version(capsys):
     assert capsys.readouterr() == ('', '')
 
 
+def test_version_parsefail_mocked(check_output):
+    check_output.return_value = b'nonversioninfo'
+    with pytest.raises(RuntimeError):
+        version()
+    check_output.assert_called_once_with(['dot', '-V'], startupinfo=STARTUPINFO,
+                                         stderr=subprocess.STDOUT)
+
+
 def test_version_mocked(check_output):
     check_output.return_value = b'dot - graphviz version 1.2.3 (mocked)'
     assert version() == (1, 2, 3)