Dynamically source version in toml from git

Instead of hard-coding the version into the pyproject.toml, we can
dynamically source it at build time.  Ideally, we want to use git
describe as a single authority source on the version.  The version is
stored in sploit.__version__ and can be consumed during sploit runtime
or during a build/package to populate the project's core metadata
version in the toml file.

hatchling provides a tool.hatch.version plugin that can read out the
variable during a build/package.  Because this variable is populated
from a git command, if the source tree isn't in a git repo, it will
fail.  In this case, sploit will report a PEP 440 compliant fake version
"0+unknown.version" to let the user know.

Because a packaged distribution doesn't exist in a git repo, we want to
bake in the version at build time into the package.  hatchling provides
a plugin to help with this, but it had some technical limitations that
didn't quite work for our use case.  Instead, I added a custom build
hook which will take the version sourced from the package (and by proxy
the git command), and overwrite the __init__.py with a hard-coded
version in the __version__ variable. This means that built/packaged
distributions of this project will have a fixed version hard-coded in
rather than dynamically sourcing from git.

The build hook operates just before the build executes.  It seems that
most build/packager front-ends (e.g. build, pip) will just run it in the
current source tree rather than making a temp copy.  This means that
when we modify the __init__.py, it is modifying our git tree.  Ideally,
we want this to be restored at the end of the build.  The build hook
interface allows us to write a hook that happens after the build, but it
won't run in the case of a crash or failed build.  Instead, I added a
custom solution to this using a member variable deconstructor.  If the
build ends in any way, the original contents of __init__.py are written
back out.

Signed-off-by: dusoleil <howcansocksbereal@gmail.com>
Reviewed-by: Malfurious <m@lfurio.us>

1 files changed, 26 insertions, 0 deletions

diff --git a/hooks/bake_version.py b/hooks/bake_version.py
new file mode 100644
index 0000000..4d43228
--- /dev/null
+++ b/hooks/bake_version.py
@@ -0,0 +1,26 @@
+from hatchling.builders.hooks.plugin.interface import BuildHookInterface
+
+import os
+import re
+
+filename = os.path.normpath(os.path.join("sploit","__init__.py"))
+
+#put the file back when the build ends
+class RestoreVersionFile:
+    def __init__(self,contents):
+        self.contents = contents
+    def __del__(self):
+        with open(filename,"w") as f:
+            f.write(self.contents)
+
+class BakeVersionBuildHook(BuildHookInterface):
+    def initialize(self,version,build_data):
+        with open(filename,"r") as f:
+            self.restore = RestoreVersionFile(f.read())
+        pattern = r'(?i)^__version__ *= *(?P<version>.+?)$'
+        match = re.search(pattern, self.restore.contents, flags=re.MULTILINE)
+        if not match:
+            raise ValueError("regex of version file failed")
+        span = match.span('version')
+        with open(filename,"w") as f:
+            f.write(f'{self.restore.contents[:span[0]]}"v{self.metadata.version}"{self.restore.contents[span[1]:]}')