Capture Ruby Version information directly from the Gemfile.lock #1603
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This class parses a Gemfile.lock for the purposes of extracting information about the Ruby version and Bundler version. Tests cases are pulled from `ruby_version_spec.rb` and from the Ruby CNB https://github.com/heroku/buildpacks-ruby/blob/e249a8bcbc75f7e5322f02bb4e32aaed50724355/commons/src/gemfile_lock.rs.
I didn't notice before, but vscode silently removed the extra space when I indented this code. There should be three spaces before the version i.e. ` 2.3.25`. Apparently `bundle platform --ruby` is not as strict and will accept two spaces. I'm unsure if there are customers relying on this behavior, running both approaches and recording metrics will answer that question.
The current code uses the output of `bundle platform --ruby` to produce a RubyVersion via `RubyVersion.bundle_platform_ruby` this adds `RubyVersion.from_gemfile_lock` that allows us to build the same value class from the raw `Gemfile.lock` file on disk (don't have to execute any Ruby code). This behavior is validated by running both modes in the `ruby_version_spec.rb` tests.
This move allows us to inject the information into language packs (not yet wired up).
Manipulating classes as variables is common, but they're usually annotated to indicate they're a class.
The dead_end gem is renamed into syntax_suggest and now comes with Ruby 3.2 (I maintain it!).
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edmorley
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May 26, 2025
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Add a custom class
GemfileLockthat parses a lockfile to return information that can build a RubyVersion. We then compare that information to the current method of usingbundle platform --rubyoutput to gauge correctness from production data before we make any behavior changes.Commits are are focused (if not entirely small) and ordered.
Context of this work
Today, the order of operations for running the buildpack looks like this:
bundle platform --rubyto detect the application Ruby version.Moving into the future, an eventual goal is to be able to avoid running
bundle platform --rubywith the bootstrap version of ruby (used by the buildpack). This execution exposes incompatibilities between the bootstrap ruby version and versions of bundler. Instead, the order will eventually be:gem install bundler -v <version>)To support this, I want to populate RubyVersion from different sources at the same time so I can compare them, instrument them, and ensure consistent platform behavior.
Worth noting that the proposed future goal is the same order of execution as the CNB (without the need to install a bootstrap ruby as the CNB is written in Rust).
GUS-W-18627780