Pypi: Restore regex support

We recently updated the `Pypi` strategy to use the PyPI JSON API and
the default strategy behavior no longer relies on a regex, so the initial implementation didn't include regex handling. This restores
support for a `livecheck` block regex by updating the `DEFAULT_BLOCK`
logic to handle an optional regex. This allows us to use a regex to
omit parts of the `info.version` value without having to duplicate
the default block logic in a `strategy` block only to use a regex.

This isn't currently necessary for any existing formulae using the
`Pypi` strategy but we have a few that needed a custom regex with
the previous strategy approach, so they may need this functionality
in the future. Besides that, restoring regex support to `Pypi`
ensures that `livecheck`/`strategy` blocks work in a fairly
consistent manner across strategies.

Library/Homebrew/livecheck/strategy/pypi.rb

@@ -20,10 +20,14 @@ class Pypi
 
         # The default `strategy` block used to extract version information when
         # a `strategy` block isn't provided.
-        DEFAULT_BLOCK = T.let(proc do |json|
-          json.dig("info", "version").presence
+        DEFAULT_BLOCK = T.let(proc do |json, regex|
+          version = json.dig("info", "version")
+          next if version.blank?
+
+          regex ? version[regex, 1] : version
         end.freeze, T.proc.params(
-          arg0: T::Hash[String, T.untyped],
+          json:  T::Hash[String, T.untyped],
+          regex: T.nilable(Regexp),
         ).returns(T.nilable(String)))
 
         # The `Regexp` used to extract the package name and suffix (e.g. file

Library/Homebrew/test/livecheck/strategy/pypi_spec.rb

@@ -8,7 +8,7 @@
   let(:pypi_url) { "https://files.pythonhosted.org/packages/ab/cd/efg/example-package-1.2.3.tar.gz" }
   let(:non_pypi_url) { "https://brew.sh/test" }
 
-  let(:regex) { /^v?(\d+(?:\.\d+)+)$/i }
+  let(:regex) { /^v?(\d+(?:\.\d+)+)/i }
 
   let(:generated) do
     {
@@ -17,25 +17,26 @@
   end
 
   # This is a limited subset of a PyPI JSON API response object, for the sake
-  # of testing.
+  # of testing. Typical versions use a `1.2.3` format but this adds a suffix,
+  # so we can test regex matching.
   let(:content) do
     <<~JSON
       {
         "info": {
-          "version": "1.2.3"
+          "version": "1.2.3-456"
         }
       }
     JSON
   end
 
-  let(:matches) { ["1.2.3"] }
+  let(:matches) { ["1.2.3-456"] }
 
   let(:find_versions_return_hash) do
     {
       matches: {
-        "1.2.3" => Version.new("1.2.3"),
+        "1.2.3-456" => Version.new("1.2.3-456"),
       },
-      regex:   nil,
+      regex:,
       url:     generated[:url],
     }
   end
@@ -76,10 +77,17 @@
       {
         cached:,
         cached_default: cached.merge({ matches: {} }),
+        cached_regex:   cached.merge({
+          matches: { "1.2.3" => Version.new("1.2.3") },
+          regex:,
+        }),
       }
     end
 
     it "finds versions in provided content" do
+      expect(pypi.find_versions(url: pypi_url, regex:, provided_content: content))
+        .to eq(match_data[:cached_regex])
+
       expect(pypi.find_versions(url: pypi_url, provided_content: content))
         .to eq(match_data[:cached])
     end
@@ -92,18 +100,22 @@
         next if match.blank?
 
         match[1]
-      end).to eq(match_data[:cached].merge({ regex: }))
+      end).to eq(match_data[:cached_regex])
 
       expect(pypi.find_versions(url: pypi_url, provided_content: content) do |json|
         json.dig("info", "version").presence
       end).to eq(match_data[:cached])
     end
 
     it "returns default match_data when block doesn't return version information" do
+      no_match_regex = /will_not_match/i
+
       expect(pypi.find_versions(url: pypi_url, provided_content: '{"info":{"version":""}}'))
         .to eq(match_data[:cached_default])
       expect(pypi.find_versions(url: pypi_url, provided_content: '{"other":true}'))
         .to eq(match_data[:cached_default])
+      expect(pypi.find_versions(url: pypi_url, regex: no_match_regex, provided_content: content))
+        .to eq(match_data[:cached_default].merge({ regex: no_match_regex }))
     end
 
     it "returns default match_data when url is blank" do