rumba: Fix version compatibility check in IrmPythonHEADmaster

Fix check_version() to use tag-level comparison instead of a
patch-range check, making it robust for dev/pre-release versions on
both rumba and PyOuroboros.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>

1 files changed, 21 insertions, 12 deletions

diff --git a/rumba/irm_backend.py b/rumba/irm_backend.py
index e859e21..9e76158 100644
--- a/rumba/irm_backend.py
+++ b/rumba/irm_backend.py
@@ -235,23 +235,32 @@ class IrmPython(IrmBackend):
     def _check_version():
         """Verify PyOuroboros is on the same patch level as Rumba.
 
-        Uses PEP 440 ordering so that dev/pre-release versions sort
-        correctly: tag 0.23.0 accepts 0.23.1.dev0 (setuptools_scm's
-        representation of the first commit after 0.23.0) because
-        0.23.0 <= 0.23.1.dev0 < 0.23.1 in PEP 440.
+        Both versions may be at the tag (e.g. 0.23.0) or past it
+        (e.g. 0.23.1.dev0+g…, setuptools_scm's representation of
+        the first commit after 0.23.0).  We recover the tag by
+        subtracting one from the patch for dev releases, then check
+        that both resolve to the same tag.
         """
         import importlib.metadata
         from rumba._version import version as rumba_ver
 
-        pyouro_ver = Version(importlib.metadata.version("PyOuroboros"))
-        floor = Version(rumba_ver)
-        parts = [int(x) for x in rumba_ver.split(".")[:3]]
-        parts[2] += 1
-        ceiling = Version(".".join(str(x) for x in parts))
-        if pyouro_ver < floor or pyouro_ver >= ceiling:
+        def _tag(ver_str):
+            v = Version(ver_str)
+            major, minor = v.release[0], v.release[1] if len(v.release) > 1 else 0
+            patch = v.release[2] if len(v.release) > 2 else 0
+            if v.is_devrelease:
+                patch -= 1
+            return "%d.%d.%d" % (major, minor, patch)
+
+        rumba_tag = _tag(rumba_ver)
+        pyouro_ver = importlib.metadata.version("PyOuroboros")
+        pyouro_tag = _tag(pyouro_ver)
+        if pyouro_tag != rumba_tag:
             raise RuntimeError(
-                "PyOuroboros >= %s, < %s required (lockstep with Rumba), "
-                "got %s" % (floor, ceiling, pyouro_ver)
+                "PyOuroboros tag %s != Rumba tag %s "
+                "(lockstep required); raw versions: "
+                "pyouroboros=%s rumba=%s"
+                % (pyouro_tag, rumba_tag, pyouro_ver, rumba_ver)
             )
 
     def _get_ipcp_type(self, layer_type):