Add better plumbing for adding more VCSStrategies

Signed-off-by: Carmen Bianca BAKKER <carmenbianca@fsfe.org>

src/reuse/project.py

@@ -34,9 +34,6 @@
 from ._util import (
     _HEADER_BYTES,
     _LICENSEREF_PATTERN,
-    GIT_EXE,
-    HG_EXE,
-    PIJUL_EXE,
     StrPath,
     _contains_snippet,
     _copyright_from_dep5,
@@ -45,14 +42,7 @@
     decoded_text_from_binary,
     extract_reuse_info,
 )
-from .vcs import (
-    VCSStrategy,
-    VCSStrategyGit,
-    VCSStrategyHg,
-    VCSStrategyNone,
-    VCSStrategyPijul,
-    find_root,
-)
+from .vcs import VCSStrategy, VCSStrategyNone, all_vcs_strategies, find_root
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -72,13 +62,10 @@ def __init__(
         if not self._root.is_dir():
             raise NotADirectoryError(f"{self._root} is no valid path")
 
-        if GIT_EXE and VCSStrategyGit.in_repo(self._root):
-            self.vcs_strategy: VCSStrategy = VCSStrategyGit(self)
-        elif HG_EXE and VCSStrategyHg.in_repo(self._root):
-            self.vcs_strategy = VCSStrategyHg(self)
-        elif PIJUL_EXE and VCSStrategyPijul.in_repo(self._root):
-            self.vcs_strategy = VCSStrategyPijul(self)
-
+        for strategy in all_vcs_strategies():
+            if strategy.EXE and strategy.in_repo(self._root):
+                self.vcs_strategy: VCSStrategy = strategy(self)
+                break
         else:
             _LOGGER.info(
                 _(

src/reuse/vcs.py

@@ -12,8 +12,9 @@
 import logging
 import os
 from abc import ABC, abstractmethod
+from inspect import isclass
 from pathlib import Path
-from typing import TYPE_CHECKING, Optional, Set
+from typing import TYPE_CHECKING, Generator, Optional, Set, Type
 
 from ._util import GIT_EXE, HG_EXE, PIJUL_EXE, StrPath, execute_command
 
@@ -26,6 +27,8 @@
 class VCSStrategy(ABC):
     """Strategy pattern for version control systems."""
 
+    EXE: str | None = None
+
     @abstractmethod
     def __init__(self, project: Project):
         self.project = project
@@ -83,9 +86,11 @@ def find_root(cls, cwd: Optional[StrPath] = None) -> Optional[Path]:
 class VCSStrategyGit(VCSStrategy):
     """Strategy that is used for Git."""
 
+    EXE = GIT_EXE
+
     def __init__(self, project: Project):
         super().__init__(project)
-        if not GIT_EXE:
+        if not self.EXE:
             raise FileNotFoundError("Could not find binary for Git")
         self._all_ignored_files = self._find_all_ignored_files()
         self._submodules = self._find_submodules()
@@ -95,7 +100,7 @@ def _find_all_ignored_files(self) -> Set[Path]:
         ignored, don't return all files inside of it.
         """
         command = [
-            str(GIT_EXE),
+            str(self.EXE),
             "ls-files",
             "--exclude-standard",
             "--ignored",
@@ -114,7 +119,7 @@ def _find_all_ignored_files(self) -> Set[Path]:
 
     def _find_submodules(self) -> Set[Path]:
         command = [
-            str(GIT_EXE),
+            str(self.EXE),
             "config",
             "-z",
             "--file",
@@ -151,7 +156,7 @@ def in_repo(cls, directory: StrPath) -> bool:
         if not Path(directory).is_dir():
             raise NotADirectoryError()
 
-        command = [str(GIT_EXE), "status"]
+        command = [str(cls.EXE), "status"]
         result = execute_command(command, _LOGGER, cwd=directory)
 
         return not result.returncode
@@ -164,7 +169,7 @@ def find_root(cls, cwd: Optional[StrPath] = None) -> Optional[Path]:
         if not Path(cwd).is_dir():
             raise NotADirectoryError()
 
-        command = [str(GIT_EXE), "rev-parse", "--show-toplevel"]
+        command = [str(cls.EXE), "rev-parse", "--show-toplevel"]
         result = execute_command(command, _LOGGER, cwd=cwd)
 
         if not result.returncode:
@@ -177,9 +182,11 @@ def find_root(cls, cwd: Optional[StrPath] = None) -> Optional[Path]:
 class VCSStrategyHg(VCSStrategy):
     """Strategy that is used for Mercurial."""
 
+    EXE = HG_EXE
+
     def __init__(self, project: Project):
         super().__init__(project)
-        if not HG_EXE:
+        if not self.EXE:
             raise FileNotFoundError("Could not find binary for Mercurial")
         self._all_ignored_files = self._find_all_ignored_files()
 
@@ -188,7 +195,7 @@ def _find_all_ignored_files(self) -> Set[Path]:
         is ignored, don't return all files inside of it.
         """
         command = [
-            str(HG_EXE),
+            str(self.EXE),
             "status",
             "--ignored",
             # terse is marked 'experimental' in the hg help but is documented
@@ -219,7 +226,7 @@ def in_repo(cls, directory: StrPath) -> bool:
         if not Path(directory).is_dir():
             raise NotADirectoryError()
 
-        command = [str(HG_EXE), "root"]
+        command = [str(cls.EXE), "root"]
         result = execute_command(command, _LOGGER, cwd=directory)
 
         return not result.returncode
@@ -232,7 +239,7 @@ def find_root(cls, cwd: Optional[StrPath] = None) -> Optional[Path]:
         if not Path(cwd).is_dir():
             raise NotADirectoryError()
 
-        command = [str(HG_EXE), "root"]
+        command = [str(cls.EXE), "root"]
         result = execute_command(command, _LOGGER, cwd=cwd)
 
         if not result.returncode:
@@ -245,15 +252,17 @@ def find_root(cls, cwd: Optional[StrPath] = None) -> Optional[Path]:
 class VCSStrategyPijul(VCSStrategy):
     """Strategy that is used for Pijul."""
 
+    EXE = PIJUL_EXE
+
     def __init__(self, project: Project):
         super().__init__(project)
-        if not PIJUL_EXE:
-            raise FileNotFoundError("Could not find binary for Mercurial")
+        if not self.EXE:
+            raise FileNotFoundError("Could not find binary for Pijul")
         self._all_tracked_files = self._find_all_tracked_files()
 
     def _find_all_tracked_files(self) -> Set[Path]:
         """Return a set of all files tracked by pijul."""
-        command = [str(PIJUL_EXE), "list"]
+        command = [str(self.EXE), "list"]
         result = execute_command(command, _LOGGER, cwd=self.project.root)
         all_files = result.stdout.decode("utf-8").splitlines()
         return {Path(file_) for file_ in all_files}
@@ -274,7 +283,7 @@ def in_repo(cls, directory: StrPath) -> bool:
         if not Path(directory).is_dir():
             raise NotADirectoryError()
 
-        command = [str(PIJUL_EXE), "diff", "--short"]
+        command = [str(cls.EXE), "diff", "--short"]
         result = execute_command(command, _LOGGER, cwd=directory)
 
         return not result.returncode
@@ -304,23 +313,27 @@ def find_root(cls, cwd: Optional[StrPath] = None) -> Optional[Path]:
             path = parent
 
 
+def all_vcs_strategies() -> Generator[Type[VCSStrategy], None, None]:
+    """Yield all VCSStrategy classes that aren't the abstract base class."""
+    for value in globals().values():
+        if (
+            isclass(value)
+            and issubclass(value, VCSStrategy)
+            and value is not VCSStrategy
+        ):
+            yield value
+
+
 def find_root(cwd: Optional[StrPath] = None) -> Optional[Path]:
     """Try to find the root of the project from *cwd*. If none is found,
     return None.
 
     Raises:
         NotADirectoryError: if directory is not a directory.
     """
-    if GIT_EXE:
-        root = VCSStrategyGit.find_root(cwd=cwd)
-        if root:
-            return root
-    if HG_EXE:
-        root = VCSStrategyHg.find_root(cwd=cwd)
-        if root:
-            return root
-    if PIJUL_EXE:
-        root = VCSStrategyPijul.find_root(cwd=cwd)
-        if root:
-            return root
+    for strategy in all_vcs_strategies():
+        if strategy.EXE:
+            root = strategy.find_root(cwd=cwd)
+            if root:
+                return root
     return None

tests/conftest.py

@@ -37,7 +37,7 @@
 except ImportError:
     sys.path.append(os.path.join(Path(__file__).parent.parent, "src"))
 finally:
-    from reuse._util import GIT_EXE, HG_EXE, setup_logging
+    from reuse._util import GIT_EXE, HG_EXE, PIJUL_EXE, setup_logging
 
 CWD = Path.cwd()
 
@@ -84,6 +84,14 @@ def hg_exe() -> str:
     return str(HG_EXE)
 
 
+@pytest.fixture()
+def pijul_exe() -> str:
+    """Run the test with Pijul."""
+    if not PIJUL_EXE:
+        pytest.skip("cannot run this test without pijul")
+    return str(PIJUL_EXE)
+
+
 @pytest.fixture(params=[True, False])
 def multiprocessing(request, monkeypatch) -> Generator[bool, None, None]:
     """Run the test with or without multiprocessing."""