Clean-up get_version_string

changelog.d/11468.misc

@@ -0,0 +1 @@
+Refactor `get_version_string` to fix-up types and duplicated code.

synapse/util/versionstring.py

@@ -1,4 +1,5 @@
 # Copyright 2016 OpenMarket Ltd
+# Copyright 2021 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -29,10 +30,11 @@ def get_version_string(module: ModuleType) -> str:
     If called on a module not in a git checkout will return `__version__`.
 
     Args:
-        module (module)
+        module: The module to check the version of. Must declare a __version__
+            attribute.
 
     Returns:
-        str
+        The module version (as a string).
     """
 
     cached_version = version_cache.get(module)
@@ -44,71 +46,36 @@ def get_version_string(module: ModuleType) -> str:
     version_string = module.__version__  # type: ignore[attr-defined]
 
     try:
-        null = open(os.devnull, "w")
-        cwd = os.path.dirname(os.path.abspath(module.__file__))
+        with open(os.devnull, "w") as null:
+            cwd = os.path.dirname(os.path.abspath(module.__file__))
+
+            def _run_git_command(prefix: str, *params: str) -> str:
+                try:
+                    result = (
+                        subprocess.check_output(["git", *params], stderr=null, cwd=cwd)
+                        .strip()
+                        .decode("ascii")
+                    )
+                    return prefix + result
+                except (subprocess.CalledProcessError, FileNotFoundError):
+                    return ""
+
+            git_branch = _run_git_command("b=", "rev-parse", "--abbrev-ref", "HEAD")
+            git_tag = _run_git_command("t=", "describe", "--exact-match")
+            git_commit = _run_git_command("", "rev-parse", "--short", "HEAD")
 
-        try:
-            git_branch = (
-                subprocess.check_output(
-                    ["git", "rev-parse", "--abbrev-ref", "HEAD"], stderr=null, cwd=cwd
-                )
-                .strip()
-                .decode("ascii")
-            )
-            git_branch = "b=" + git_branch
-        except (subprocess.CalledProcessError, FileNotFoundError):
-            # FileNotFoundError can arise when git is not installed
-            git_branch = ""
-
-        try:
-            git_tag = (
-                subprocess.check_output(
-                    ["git", "describe", "--exact-match"], stderr=null, cwd=cwd
-                )
-                .strip()
-                .decode("ascii")
-            )
-            git_tag = "t=" + git_tag
-        except (subprocess.CalledProcessError, FileNotFoundError):
-            git_tag = ""
-
-        try:
-            git_commit = (
-                subprocess.check_output(
-                    ["git", "rev-parse", "--short", "HEAD"], stderr=null, cwd=cwd
-                )
-                .strip()
-                .decode("ascii")
-            )
-        except (subprocess.CalledProcessError, FileNotFoundError):
-            git_commit = ""
-
-        try:
             dirty_string = "-this_is_a_dirty_checkout"
-            is_dirty = (
-                subprocess.check_output(
-                    ["git", "describe", "--dirty=" + dirty_string], stderr=null, cwd=cwd
+            is_dirty = _run_git_command(
+                "", "describe", "--dirty=" + dirty_string
+            ).endswith(dirty_string)
+            git_dirty = "dirty" if is_dirty else ""
+
+            if git_branch or git_tag or git_commit or git_dirty:
+                git_version = ",".join(
+                    s for s in (git_branch, git_tag, git_commit, git_dirty) if s
                 )
-                .strip()
-                .decode("ascii")
-                .endswith(dirty_string)
-            )
 
-            git_dirty = "dirty" if is_dirty else ""
-        except (subprocess.CalledProcessError, FileNotFoundError):
-            git_dirty = ""
-
-        if git_branch or git_tag or git_commit or git_dirty:
-            git_version = ",".join(
-                s for s in (git_branch, git_tag, git_commit, git_dirty) if s
-            )
-
-            version_string = "%s (%s)" % (
-                # If the __version__ attribute doesn't exist, we'll have failed
-                # loudly above.
-                module.__version__,  # type: ignore[attr-defined]
-                git_version,
-            )
+                version_string = f"{version_string} ({git_version})"
     except Exception as e:
         logger.info("Failed to check for git repository: %s", e)