fix #1052: use consistent node hash length

Author: RonnyPfannschmidt

.cursor/rules/test-running.mdc

@@ -6,3 +6,7 @@ alwaysApply: true
 
 use `uv run pytest` to run tests
 use uv to manage dependencies
+
+follow preexisting conventions in the project
+
+- use the fixtures

src/setuptools_scm/_integration/dump_version.py

@@ -6,11 +6,29 @@
 
 from .. import _types as _t
 from .._log import log as parent_log
+from .._node_utils import _format_node_for_output
 from .._version_cls import _version_as_tuple
 from ..version import ScmVersion
 
 log = parent_log.getChild("dump_version")
 
+
+class _TemplateScmVersion:
+    """Wrapper for ScmVersion that formats node for template output."""
+
+    def __init__(self, scm_version: ScmVersion) -> None:
+        self._scm_version = scm_version
+
+    def __getattr__(self, name: str) -> object:
+        # Delegate all attribute access to the wrapped ScmVersion
+        return getattr(self._scm_version, name)
+
+    @property
+    def node(self) -> str | None:
+        """Return the node formatted for output."""
+        return _format_node_for_output(self._scm_version.node)
+
+
 TEMPLATES = {
     ".py": """\
 # file generated by setuptools-scm
@@ -101,10 +119,12 @@ def write_version_to_path(
     log.debug("dump %s into %s", version, target)
     version_tuple = _version_as_tuple(version)
     if scm_version is not None:
+        # Wrap ScmVersion to provide formatted node for templates
+        template_scm_version = _TemplateScmVersion(scm_version)
         content = final_template.format(
             version=version,
             version_tuple=version_tuple,
-            scm_version=scm_version,
+            scm_version=template_scm_version,
         )
     else:
         content = final_template.format(version=version, version_tuple=version_tuple)

src/setuptools_scm/_node_utils.py

@@ -0,0 +1,46 @@
+"""Private utilities for consistent node ID handling across SCM backends."""
+
+from __future__ import annotations
+
+# Standard node ID length used across all SCM backends
+_NODE_ID_LENGTH = 10
+
+
+def _slice_node_id(node_id: str) -> str:
+    """
+    Slice a node ID to a consistent length.
+
+    This ensures that all SCM backends (git, mercurial, archival)
+    return the same length node IDs for consistency.
+
+    Args:
+        node_id: The full node ID/hash from the SCM
+
+    Returns:
+        The node ID sliced to the standard length
+    """
+    return node_id[:_NODE_ID_LENGTH]
+
+
+def _format_node_for_output(node_id: str | None) -> str | None:
+    """
+    Format a node ID for output, applying consistent slicing.
+
+    Args:
+        node_id: The full node ID/hash from the SCM or None
+
+    Returns:
+        The node ID sliced to standard length for output, or None if input was None
+    """
+    if node_id is None:
+        return None
+
+    # Handle mercurial nodes with 'h' prefix
+    if node_id.startswith("h"):
+        # For mercurial nodes, slice the part after 'h' and reconstruct
+        hg_hash = node_id[1:]  # Remove 'h' prefix
+        sliced_hash = _slice_node_id(hg_hash)
+        return "h" + sliced_hash
+
+    # For git nodes (with or without 'g' prefix) and others
+    return _slice_node_id(node_id)

src/setuptools_scm/git.py

@@ -2,7 +2,6 @@
 
 import dataclasses
 import logging
-import operator
 import os
 import re
 import shlex
@@ -47,6 +46,7 @@
     "--dirty",
     "--tags",
     "--long",
+    "--abbrev=40",
     "--match",
     "*[0-9]*",
 ]
@@ -174,12 +174,10 @@ def fetch_shallow(self) -> None:
         run_git(["fetch", "--unshallow"], self.path, check=True, timeout=240)
 
     def node(self) -> str | None:
-        unsafe_short_node = operator.itemgetter(slice(7))
-
         return run_git(
             ["rev-parse", "--verify", "--quiet", "HEAD"], self.path
         ).parse_success(
-            parse=unsafe_short_node,
+            parse=str,
         )
 
     def count_all_nodes(self) -> int:

src/setuptools_scm/hg.py

@@ -66,7 +66,7 @@ def get_meta(self, config: Configuration) -> ScmVersion | None:
         if self._is_initial_node(node):
             return self._create_initial_meta(config, dirty, branch, node_date)
 
-        node = "h" + node[:7]
+        node = "h" + node
         tags = self._parse_tags(tags_str)
 
         # Try to get version from current tags
@@ -285,7 +285,7 @@ def parse(root: _t.PathT, config: Configuration) -> ScmVersion | None:
 
 def archival_to_version(data: dict[str, str], config: Configuration) -> ScmVersion:
     log.debug("data %s", data)
-    node = data.get("node", "")[:12]
+    node = data.get("node", "")
     if node:
         node = "h" + node
     if "tag" in data:

src/setuptools_scm/hg_git.py

@@ -119,7 +119,7 @@ def node(self) -> str | None:
 
                 return hg_node
 
-        return git_node[:7]
+        return git_node
 
     def count_all_nodes(self) -> int:
         res = run_hg(["log", "-r", "ancestors(.)", "-T", "."], cwd=self.path)

src/setuptools_scm/version.py

@@ -16,6 +16,7 @@
 
 from . import _entrypoints
 from . import _modify_version
+from ._node_utils import _format_node_for_output
 
 if TYPE_CHECKING:
     import sys
@@ -170,7 +171,7 @@ def format_with(self, fmt: str, **kw: object) -> str:
             time=self.time,
             tag=self.tag,
             distance=self.distance,
-            node=self.node,
+            node=_format_node_for_output(self.node),
             dirty=self.dirty,
             branch=self.branch,
             node_date=self.node_date,

testing/test_mercurial.py

@@ -31,12 +31,12 @@ def wd(wd: WorkDir) -> WorkDir:
 
 archival_mapping = {
     "1.0": {"tag": "1.0"},
-    "1.1.0.dev3+h000000000000": {
+    "1.1.0.dev3+h0000000000": {
         "latesttag": "1.0",
         "latesttagdistance": "3",
         "node": "0" * 20,
     },
-    "1.0.1.dev3+h000000000000": {
+    "1.0.1.dev3+h0000000000": {
         "latesttag": "1.0.0",
         "latesttagdistance": "3",
         "branch": "1.0",
@@ -163,7 +163,7 @@ def test_version_from_archival(wd: WorkDir) -> None:
 """,
     )
 
-    assert wd.get_version() == "0.2.dev3+h000000000000"
+    assert wd.get_version() == "0.2.dev3+h0000000000"
 
 
 @pytest.mark.issue("#72")