fix #213: better error on nonzero dev versions

5 files changed, 28 insertions, 1 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index dbce446..c570357 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -12,6 +12,7 @@ v4.2.0
 * add a version_tuple to write_to templates
 * fix #321: add suppport for the ``SETUPTOOLS_SCM_PRETEND_VERSION_FOR_${DISTRIBUTION_NAME}`` env var to target the pretend key
 * fix #142: clearly list supported scm
+* fix #213: better error message for non-zero dev numbers in tags
 
 
 v4.1.2
diff --git a/README.rst b/README.rst
index a826b1f..f9193c1 100644
--- a/README.rst
+++ b/README.rst
@@ -277,6 +277,7 @@ distance and not clean:
 The next version is calculated by adding ``1`` to the last numeric component of
 the tag.
 
+
 For Git projects, the version relies on `git describe <https://git-scm.com/docs/git-describe>`_,
 so you will see an additional ``g`` prepended to the ``{revision hash}``.
 
@@ -507,6 +508,8 @@ Version number construction
     :guess-next-dev: Automatically guesses the next development version (default).
         Guesses the upcoming release by incrementing the pre-release segment if present,
         otherwise by incrementing the micro segment. Then appends :code:`.devN`.
+        In case the tag ends with ``.dev0`` the version is not bumped
+        and custom ``.devN`` versions will trigger a error.
     :post-release: generates post release versions (adds :code:`.postN`)
     :python-simplified-semver: Basic semantic versioning. Guesses the upcoming release
         by incrementing the minor segment and setting the micro segment to zero if the
diff --git a/src/setuptools_scm/version.py b/src/setuptools_scm/version.py
index 40eadc8..f97dca5 100644
--- a/src/setuptools_scm/version.py
+++ b/src/setuptools_scm/version.py
@@ -230,7 +230,13 @@ def _bump_dev(version):
         return
 
     prefix, tail = version.rsplit(".dev", 1)
-    assert tail == "0", "own dev numbers are unsupported"
+    if tail != "0":
+        raise ValueError(
+            "choosing custom numbers for the `.devX` distance "
+            "is not supported.\n "
+            "The {version} can't be bumped\n"
+            "Please drop the tag or create a new supported one".format(version=version)
+        )
     return prefix
 
 
diff --git a/testing/test_version.py b/testing/test_version.py
index 722b8e8..ee13801 100644
--- a/testing/test_version.py
+++ b/testing/test_version.py
@@ -120,6 +120,22 @@ def test_no_guess_version(version, expected_next):
     assert computed == expected_next
 
 
+def test_bump_dev_version_zero():
+    guess_next_version("1.0.dev0")
+
+
+def test_bump_dev_version_nonzero_raises():
+    with pytest.raises(ValueError) as excinfo:
+        guess_next_version("1.0.dev1")
+
+    assert str(excinfo.value) == (
+        "choosing custom numbers for the `.devX` distance "
+        "is not supported.\n "
+        "The 1.0.dev1 can't be bumped\n"
+        "Please drop the tag or create a new supported one"
+    )
+
+
 @pytest.mark.parametrize(
     "tag, expected",
     [
diff --git a/tox.ini b/tox.ini
index 5f1143e..030dbd4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -48,6 +48,7 @@ setenv = SETUPTOOLS_SCM_PRETEND_VERSION=2.0
 deps=
     check-manifest
     docutils
+    pygments
 commands=
     rst2html.py README.rst {envlogdir}/README.html --strict []
     check-manifest