sort out parse_version debugging, fixes #261

4 files changed, 22 insertions, 17 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 55810d0..41d16bf 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -4,6 +4,8 @@ v3.0.0
 * introduce pre-commit and use black
 * print the origin module to help testing
 * switch to src layout
+* no longer alias tag and parsed_version in order to support understanding a version parse failure
+* require parse results to be ScmVersion or None
 
 v2.1.0
 ======
diff --git a/src/setuptools_scm/__init__.py b/src/setuptools_scm/__init__.py
index 4beef3a..6b61b3f 100644
--- a/src/setuptools_scm/__init__.py
+++ b/src/setuptools_scm/__init__.py
@@ -7,7 +7,7 @@ import sys
 import warnings
 
 from .utils import trace
-from .version import format_version, meta, ScmVersion
+from .version import format_version, meta
 from .discover import iter_matching_entrypoints
 
 PRETEND_KEY = "SETUPTOOLS_SCM_PRETEND_VERSION"
@@ -46,15 +46,14 @@ def dump_version(root, version, write_to, template=None):
     ext = os.path.splitext(target)[1]
     template = template or TEMPLATES.get(ext)
 
-    if template is not None:
-        dump = template.format(version=version)
-    else:
+    if template is None:
         raise ValueError(
-            ("bad file format: '%s' (of %s) \n" "only *.txt and *.py are supported")
-            % (os.path.splitext(target)[1], target)
+            "bad file format: '{}' (of {}) \nonly *.txt and *.py are supported".format(
+                os.path.splitext(target)[1], target
+            )
         )
     with open(target, "w") as fp:
-        fp.write(dump)
+        fp.write(template.format(version=version))
 
 
 def _do_parse(root, parse):
@@ -68,12 +67,12 @@ def _do_parse(root, parse):
         parse_result = parse(root)
         if isinstance(parse_result, string_types):
             warnings.warn(
-                "version parse result was a string\n" "please return a parsed version",
+                "version parse result was a string\nplease return a parsed version",
                 category=DeprecationWarning,
             )
             # we use ScmVersion here in order to keep legacy code working
             # for 2.0 we should use meta
-            parse_result = ScmVersion(parse_result)
+            parse_result = meta(parse_result)
         version = parse_result or _version_from_entrypoint(
             root, "setuptools_scm.parse_scm_fallback"
         )
diff --git a/src/setuptools_scm/version.py b/src/setuptools_scm/version.py
index e49a688..2b9037f 100644
--- a/src/setuptools_scm/version.py
+++ b/src/setuptools_scm/version.py
@@ -8,7 +8,7 @@ from .utils import trace
 
 from pkg_resources import iter_entry_points
 
-from pkg_resources import parse_version
+from pkg_resources import parse_version as pkg_parse_version
 
 SEMVER_MINOR = 2
 SEMVER_PATCH = 3
@@ -21,7 +21,7 @@ def _pad(iterable, size, padding=None):
 
 
 def _get_version_class():
-    modern_version = parse_version("1.0")
+    modern_version = pkg_parse_version("1.0")
     if isinstance(modern_version, tuple):
         return None
     else:
@@ -66,7 +66,7 @@ def tag_to_version(tag):
     version = tag.rsplit("-", 1)[-1].lstrip("v")
     if VERSION_CLASS is None:
         return version
-    version = parse_version(version)
+    version = pkg_parse_version(version)
     trace("version", repr(version))
     if isinstance(version, VERSION_CLASS):
         return version
@@ -140,10 +140,10 @@ def _parse_tag(tag, preformatted):
 
 
 def meta(tag, distance=None, dirty=False, node=None, preformatted=False, **kw):
-    tag = _parse_tag(tag, preformatted)
-    trace("version", tag)
-    assert tag is not None, "cant parse version %s" % tag
-    return ScmVersion(tag, distance, node, dirty, preformatted, **kw)
+    parsed_version = _parse_tag(tag, preformatted)
+    trace("version", tag, "->", parsed_version)
+    assert parsed_version is not None, "cant parse version %s" % tag
+    return ScmVersion(parsed_version, distance, node, dirty, preformatted, **kw)
 
 
 def guess_next_version(tag_version):
diff --git a/tox.ini b/tox.ini
index 864b7b1..1281b87 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist=py{27,34,35,36,37}-test,flake8,check_readme
+envlist=py{27,34,35,36,37}-test,flake8,check_readme,py{27,36}-selftest
 
 [flake8]
 max-complexity = 10
@@ -15,10 +15,14 @@ exclude=
 
 [testenv]
 usedevelop=True
+skip_install=
+    selfcheck: True
+    test: False
 deps=
     pytest
 commands=
     test: py.test []
+    selfcheck: python setup.py --version
 
 [testenv:flake8]
 skip_install=True