Implement Mercurial support (#699)

Author: adiroiban

pyproject.toml

@@ -164,6 +164,9 @@ skip_covered = true
 exclude_lines = [
     "pragma: no cover",
     "if TYPE_CHECKING:",
+    # Empty functions of a Protocol definition (used in _vcs.py) can never be
+    # executed. Ignoring them.
+    ": \\.\\.\\.$",
 ]
 omit = [
     "src/towncrier/__main__.py",

src/towncrier/_git.py

@@ -5,21 +5,33 @@
 
 import os
 
-from subprocess import STDOUT, CalledProcessError, call, check_output
+from subprocess import STDOUT, call, check_output
+from typing import Container
+from warnings import warn
+
+
+def get_default_compare_branch(branches: Container[str]) -> str | None:
+    if "origin/main" in branches:
+        return "origin/main"
+    if "origin/master" in branches:
+        warn(
+            'Using "origin/master" as default compare branch is deprecated '
+            "and will be removed in a future version.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return "origin/master"
+    return None
 
 
 def remove_files(fragment_filenames: list[str]) -> None:
     if not fragment_filenames:
         return
 
     # Filter out files that are unknown to git
-    try:
-        git_fragments = check_output(
-            ["git", "ls-files"] + fragment_filenames, encoding="utf-8"
-        ).split("\n")
-    except CalledProcessError:
-        # we may not be in a git repository
-        git_fragments = []
+    git_fragments = check_output(
+        ["git", "ls-files"] + fragment_filenames, encoding="utf-8"
+    ).split("\n")
 
     git_fragments = [os.path.abspath(f) for f in git_fragments if os.path.isfile(f)]
     call(["git", "rm", "--quiet", "--force"] + git_fragments)

src/towncrier/_hg.py

@@ -0,0 +1,63 @@
+# Copyright (c) towncrier contributors, 2025
+# See LICENSE for details.
+
+from __future__ import annotations
+
+import os
+
+from subprocess import STDOUT, call, check_output
+from typing import Container
+
+
+def get_default_compare_branch(branches: Container[str]) -> str | None:
+    if "default" in branches:
+        return "default"
+    return None
+
+
+def remove_files(fragment_filenames: list[str]) -> None:
+    if not fragment_filenames:
+        return
+
+    # Filter out files that are unknown to mercurial
+    hg_fragments = (
+        check_output(["hg", "files"] + fragment_filenames, encoding="utf-8")
+        .strip()
+        .split("\n")
+    )
+
+    hg_fragments = [os.path.abspath(f) for f in hg_fragments if os.path.isfile(f)]
+    fragment_filenames = [
+        os.path.abspath(f) for f in fragment_filenames if os.path.isfile(f)
+    ]
+    call(["hg", "rm", "--force"] + hg_fragments, encoding="utf-8")
+    unknown_fragments = set(fragment_filenames) - set(hg_fragments)
+    for unknown_fragment in unknown_fragments:
+        os.remove(unknown_fragment)
+
+
+def stage_newsfile(directory: str, filename: str) -> None:
+    call(["hg", "add", os.path.join(directory, filename)])
+
+
+def get_remote_branches(base_directory: str) -> list[str]:
+    branches = check_output(
+        ["hg", "branches", "--template", "{branch}\n"],
+        cwd=base_directory,
+        encoding="utf-8",
+    ).splitlines()
+
+    return branches
+
+
+def list_changed_files_compared_to_branch(
+    base_directory: str, compare_with: str, include_staged: bool
+) -> list[str]:
+    output = check_output(
+        ["hg", "diff", "--stat", "-r", compare_with],
+        cwd=base_directory,
+        encoding="utf-8",
+        stderr=STDOUT,
+    ).splitlines()
+
+    return [line.split("|")[0].strip() for line in output if "|" in line]

src/towncrier/_novcs.py

@@ -0,0 +1,34 @@
+# Copyright (c) towncrier contributors, 2025
+# See LICENSE for details.
+
+from __future__ import annotations
+
+import os
+
+from typing import Container
+
+
+def get_default_compare_branch(branches: Container[str]) -> str | None:
+    return None
+
+
+def remove_files(fragment_filenames: list[str]) -> None:
+    if not fragment_filenames:
+        return
+
+    for fragment in fragment_filenames:
+        os.remove(fragment)
+
+
+def stage_newsfile(directory: str, filename: str) -> None:
+    return
+
+
+def get_remote_branches(base_directory: str) -> list[str]:
+    return []
+
+
+def list_changed_files_compared_to_branch(
+    base_directory: str, compare_with: str, include_staged: bool
+) -> list[str]:
+    return []

src/towncrier/_vcs.py

@@ -0,0 +1,72 @@
+# Copyright (c) towncrier contributors, 2025
+# See LICENSE for details.
+
+from __future__ import annotations
+
+import os
+
+from typing import Container, Protocol
+
+
+class VCSMod(Protocol):
+    def get_default_compare_branch(self, branches: Container[str]) -> str | None: ...
+    def remove_files(self, fragment_filenames: list[str]) -> None: ...
+    def stage_newsfile(self, directory: str, filename: str) -> None: ...
+    def get_remote_branches(self, base_directory: str) -> list[str]: ...
+
+    def list_changed_files_compared_to_branch(
+        self, base_directory: str, compare_with: str, include_staged: bool
+    ) -> list[str]: ...
+
+
+def _get_mod(base_directory: str) -> VCSMod:
+    base_directory = os.path.abspath(base_directory)
+    if os.path.exists(os.path.join(base_directory, ".git")):
+        from . import _git
+
+        return _git
+    elif os.path.exists(os.path.join(base_directory, ".hg")):
+        from . import _hg
+
+        hg: VCSMod = _hg
+
+        return hg
+    else:
+        # No VCS was found in the current directory
+        # We will try our luck in the parent directory.
+        parent = os.path.dirname(base_directory)
+        if parent == base_directory:
+            # We reached the fs root, abandoning
+            from . import _novcs
+
+            return _novcs
+
+        return _get_mod(parent)
+
+
+def get_default_compare_branch(
+    base_directory: str, branches: Container[str]
+) -> str | None:
+    return _get_mod(base_directory).get_default_compare_branch(branches)
+
+
+def remove_files(base_directory: str, fragment_filenames: list[str]) -> None:
+    return _get_mod(base_directory).remove_files(fragment_filenames)
+
+
+def stage_newsfile(directory: str, filename: str) -> None:
+    return _get_mod(directory).stage_newsfile(directory, filename)
+
+
+def get_remote_branches(base_directory: str) -> list[str]:
+    return _get_mod(base_directory).get_remote_branches(base_directory)
+
+
+def list_changed_files_compared_to_branch(
+    base_directory: str, compare_with: str, include_staged: bool
+) -> list[str]:
+    return _get_mod(base_directory).list_changed_files_compared_to_branch(
+        base_directory,
+        compare_with,
+        include_staged,
+    )

src/towncrier/build.py

@@ -17,7 +17,7 @@
 
 from click import Context, Option, UsageError
 
-from towncrier import _git
+from towncrier import _vcs
 
 from ._builder import find_fragments, render_fragments, split_fragments
 from ._project import get_project_name, get_version
@@ -270,15 +270,15 @@ def __main(
     )
 
     click.echo("Staging newsfile...", err=to_err)
-    _git.stage_newsfile(base_directory, news_file)
+    _vcs.stage_newsfile(base_directory, news_file)
 
     if should_remove_fragment_files(
         fragment_filenames,
         answer_yes,
         answer_keep,
     ):
         click.echo("Removing news fragments...", err=to_err)
-        _git.remove_files(fragment_filenames)
+        _vcs.remove_files(base_directory, fragment_filenames)
 
     click.echo("Done!", err=to_err)
 

src/towncrier/check.py

@@ -8,28 +8,16 @@
 import sys
 
 from subprocess import CalledProcessError
-from typing import Container
-from warnings import warn
 
 import click
 
 from ._builder import find_fragments
-from ._git import get_remote_branches, list_changed_files_compared_to_branch
 from ._settings import config_option_help, load_config_from_options
-
-
-def _get_default_compare_branch(branches: Container[str]) -> str | None:
-    if "origin/main" in branches:
-        return "origin/main"
-    if "origin/master" in branches:
-        warn(
-            'Using "origin/master" as default compare branch is deprecated '
-            "and will be removed in a future version.",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-        return "origin/master"
-    return None
+from ._vcs import (
+    get_default_compare_branch,
+    get_remote_branches,
+    list_changed_files_compared_to_branch,
+)
 
 
 @click.command(name="check")
@@ -82,8 +70,8 @@ def __main(
     base_directory, config = load_config_from_options(directory, config_path)
 
     if comparewith is None:
-        comparewith = _get_default_compare_branch(
-            get_remote_branches(base_directory=base_directory)
+        comparewith = get_default_compare_branch(
+            base_directory, get_remote_branches(base_directory=base_directory)
         )
 
     if comparewith is None:

src/towncrier/newsfragments/394.feature.rst

@@ -0,0 +1 @@
+Support was added for Mercurial SCM.

src/towncrier/test/test_check.py

@@ -3,15 +3,13 @@
 
 import os
 import os.path
-import warnings
 
 from pathlib import Path
 from subprocess import check_call
 
 from click.testing import CliRunner
 from twisted.trial.unittest import TestCase
 
-from towncrier import check
 from towncrier.build import _main as towncrier_build
 from towncrier.check import _main as towncrier_check
 
@@ -401,24 +399,6 @@ def test_get_default_compare_branch_missing(self):
         self.assertEqual(1, result.exit_code)
         self.assertEqual("Could not detect default branch. Aborting.\n", result.output)
 
-    def test_get_default_compare_branch_main(self):
-        """
-        If there's a remote branch origin/main, prefer it over everything else.
-        """
-        branch = check._get_default_compare_branch(["origin/master", "origin/main"])
-
-        self.assertEqual("origin/main", branch)
-
-    def test_get_default_compare_branch_fallback(self):
-        """
-        If there's origin/master and no main, use it and warn about it.
-        """
-        with warnings.catch_warnings(record=True) as w:
-            branch = check._get_default_compare_branch(["origin/master", "origin/foo"])
-
-        self.assertEqual("origin/master", branch)
-        self.assertTrue(w[0].message.args[0].startswith('Using "origin/master'))
-
     @with_isolated_runner
     def test_in_different_dir_with_nondefault_newsfragments_directory(self, runner):
         """

src/towncrier/test/test_git.py

@@ -2,6 +2,8 @@
 # See LICENSE for details.
 
 
+import warnings
+
 from twisted.trial.unittest import TestCase
 
 from towncrier import _git
@@ -13,3 +15,21 @@ def test_empty_remove(self):
         If remove_files gets an empty list, it returns gracefully.
         """
         _git.remove_files([])
+
+    def test_get_default_compare_branch_main(self):
+        """
+        If there's a remote branch origin/main, prefer it over everything else.
+        """
+        branch = _git.get_default_compare_branch(["origin/master", "origin/main"])
+
+        self.assertEqual("origin/main", branch)
+
+    def test_get_default_compare_branch_fallback(self):
+        """
+        If there's origin/master and no main, use it and warn about it.
+        """
+        with warnings.catch_warnings(record=True) as w:
+            branch = _git.get_default_compare_branch(["origin/master", "origin/foo"])
+
+        self.assertEqual("origin/master", branch)
+        self.assertTrue(w[0].message.args[0].startswith('Using "origin/master'))