Add metrics for the existence of a uv lockfile

To help gauge how often a uv lockfile exists. (Either from
someone trying to use uv and the build failing, or when a
third-party buildpack is used to export the uv lockfile to a
requirements file etc).

Towards #1616.
GUS-W-17431743.

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## [Unreleased]
 
 - Fixed Dev Center links to reflect recent article URL changes. ([#1723](https://github.com/heroku/heroku-buildpack-python/pull/1723))
+- Added metrics for the existence of a uv lockfile. ([#1725](https://github.com/heroku/heroku-buildpack-python/pull/1725))
 
 ## [v271] - 2024-12-12
 

bin/report

@@ -94,6 +94,7 @@ ALL_OTHER_FIELDS=(
 	setup_py_only
 	sqlite_install_duration
 	total_duration
+	uv_lockfile
 )
 
 for field in "${STRING_FIELDS[@]}"; do

lib/package_manager.sh

@@ -59,6 +59,10 @@ function package_manager::determine_package_manager() {
 		meta_set "setup_py_only" "false"
 	fi
 
+	if [[ -f "${build_dir}/uv.lock" ]]; then
+		meta_set "uv_lockfile" "true"
+	fi
+
 	local num_package_managers_found=${#package_managers_found[@]}
 
 	case "${num_package_managers_found}" in
@@ -87,6 +91,11 @@ function package_manager::determine_package_manager() {
 				Otherwise, add a package manager file to your app. If your app has
 				no dependencies, then create an empty 'requirements.txt' file.
 
+				If you would like to see support for the package manager uv,
+				please vote and comment on these GitHub issues:
+				https://github.com/heroku/heroku-buildpack-python/issues/1616
+				https://github.com/heroku/roadmap/issues/323
+
 				For help with using Python on Heroku, see:
 				https://devcenter.heroku.com/articles/getting-started-with-python
 				https://devcenter.heroku.com/articles/python-support

spec/hatchet/package_manager_spec.rb

@@ -31,6 +31,53 @@
           remote:  !     Otherwise, add a package manager file to your app. If your app has
           remote:  !     no dependencies, then create an empty 'requirements.txt' file.
           remote:  !     
+          remote:  !     If you would like to see support for the package manager uv,
+          remote:  !     please vote and comment on these GitHub issues:
+          remote:  !     https://github.com/heroku/heroku-buildpack-python/issues/1616
+          remote:  !     https://github.com/heroku/roadmap/issues/323
+          remote:  !     
+          remote:  !     For help with using Python on Heroku, see:
+          remote:  !     https://devcenter.heroku.com/articles/getting-started-with-python
+          remote:  !     https://devcenter.heroku.com/articles/python-support
+          remote: 
+          remote:  !     Push rejected, failed to compile Python app.
+        OUTPUT
+      end
+    end
+  end
+
+  context 'when there is a uv.lock' do
+    let(:app) { Hatchet::Runner.new('spec/fixtures/uv_lockfile_only', allow_failure: true) }
+
+    it 'fails the build with an informative error message' do
+      app.deploy do |app|
+        expect(clean_output(app.output)).to include(<<~OUTPUT)
+          remote: -----> Python app detected
+          remote: 
+          remote:  !     Error: Couldn't find any supported Python package manager files.
+          remote:  !     
+          remote:  !     A Python app on Heroku must have either a 'requirements.txt',
+          remote:  !     'Pipfile' or 'poetry.lock' package manager file in the root
+          remote:  !     directory of its source code.
+          remote:  !     
+          remote:  !     Currently the root directory of your app contains:
+          remote:  !     
+          remote:  !     uv.lock
+          remote:  !     
+          remote:  !     If your app already has a package manager file, check that it:
+          remote:  !     
+          remote:  !     1. Is in the top level directory (not a subdirectory).
+          remote:  !     2. Has the correct spelling (the filenames are case-sensitive).
+          remote:  !     3. Isn't listed in '.gitignore' or '.slugignore'.
+          remote:  !     
+          remote:  !     Otherwise, add a package manager file to your app. If your app has
+          remote:  !     no dependencies, then create an empty 'requirements.txt' file.
+          remote:  !     
+          remote:  !     If you would like to see support for the package manager uv,
+          remote:  !     please vote and comment on these GitHub issues:
+          remote:  !     https://github.com/heroku/heroku-buildpack-python/issues/1616
+          remote:  !     https://github.com/heroku/roadmap/issues/323
+          remote:  !     
           remote:  !     For help with using Python on Heroku, see:
           remote:  !     https://devcenter.heroku.com/articles/getting-started-with-python
           remote:  !     https://devcenter.heroku.com/articles/python-support