Refactor Go proxy models

- Reduce coupling between GoModule and VersionFinder
- Do not fetch go.mod when blobs have already been fetched

ee/app/finders/packages/go/version_finder.rb

@@ -14,7 +14,7 @@ module Packages
       def execute
         @mod.project.repository.tags
           .filter { |tag| semver? tag }
-          .map    { |tag| find_ref tag }
+          .map    { |tag| @mod.version_by(ref: tag) }
           .filter { |ver| ver.valid? }
       end
 
@@ -22,55 +22,23 @@ module Packages
         case target
         when String
           if pseudo_version? target
-            find_pseudo_version target
+            semver = parse_semver(target)
+            commit = pseudo_version_commit(@mod.project, semver)
+            Packages::GoModuleVersion.new(@mod, :pseudo, commit, name: target, semver: semver)
           else
-            mod.versions.find { |v| v.name == target }
+            @mod.version_by(ref: target)
           end
 
         when Gitlab::Git::Ref
-          find_ref target
+          @mod.version_by(ref: target)
 
         when ::Commit, Gitlab::Git::Commit
-          find_commit target
+          @mod.version_by(commit: target)
 
         else
           raise ArgumentError.new 'not a valid target'
         end
       end
-
-      private
-
-      def find_ref(ref)
-        commit = ref.dereferenced_target
-        Packages::GoModuleVersion.new(@mod, :ref, commit, ref: ref, semver: parse_semver(ref.name))
-      end
-
-      def find_commit(commit)
-        Packages::GoModuleVersion.new(@mod, :commit, commit)
-      end
-
-      def find_pseudo_version(str)
-        semver = parse_semver(str)
-        raise ArgumentError.new 'target is not a pseudo-version' unless pseudo_version?(semver)
-
-        # valid pseudo-versions are
-        #   vX.0.0-yyyymmddhhmmss-sha1337beef0, when no earlier tagged commit exists for X
-        #   vX.Y.Z-pre.0.yyyymmddhhmmss-sha1337beef0, when most recent prior tag is vX.Y.Z-pre
-        #   vX.Y.(Z+1)-0.yyyymmddhhmmss-sha1337beef0, when most recent prior tag is vX.Y.Z
-
-        # go discards the timestamp when resolving pseudo-versions, so we will do the same
-
-        timestamp, sha = semver.prerelease.split('-').last 2
-        timestamp = timestamp.split('.').last
-        commit = @mod.project.repository.commit_by(oid: sha)
-
-        # these errors are copied from proxy.golang.org's responses
-        raise ArgumentError.new 'invalid pseudo-version: unknown commit' unless commit
-        raise ArgumentError.new 'invalid pseudo-version: revision is shorter than canonical' unless sha.length == 12
-        raise ArgumentError.new 'invalid pseudo-version: does not match version-control timestamp' unless commit.committed_date.strftime('%Y%m%d%H%M%S') == timestamp
-
-        Packages::GoModuleVersion.new(@mod, :pseudo, commit, name: str, semver: semver)
-      end
     end
   end
 end

ee/app/models/packages/go_module.rb

@@ -13,8 +13,19 @@ class Packages::GoModule
     @versions ||= Packages::Go::VersionFinder.new(self).execute
   end
 
-  def find_version(name)
-    Packages::Go::VersionFinder.new(self).find(name)
+  def version_by(ref: nil, commit: nil)
+    raise ArgumentError.new 'no filter specified' unless ref || commit
+    raise ArgumentError.new 'ref and commit are mutually exclusive' if ref && commit
+
+    if commit
+      return version_by_sha(commit) if commit.is_a? String
+
+      return version_by_commit(commit)
+    end
+
+    return version_by_name(ref) if ref.is_a? String
+
+    version_by_ref(ref)
   end
 
   def path_valid?(major)
@@ -31,4 +42,42 @@ class Packages::GoModule
   def gomod_valid?(gomod)
     gomod&.split("\n", 2)&.first == "module #{@name}"
   end
+
+  private
+
+  def version_by_name(name)
+    # avoid a Gitaly call if possible
+    if defined?(@versions)
+      v = @versions.find { |v| v.name == ref }
+      return v if v
+    end
+
+    ref = @project.repository.find_tag(name) || @project.repository.find_branch(name)
+    return unless ref
+
+    version_by_ref(ref)
+  end
+
+  def version_by_ref(ref)
+    # reuse existing versions
+    if defined?(@versions)
+      v = @versions.find { |v| v.ref == ref }
+      return v if v
+    end
+
+    commit = ref.dereferenced_target
+    semver = Packages::SemVer.parse(ref.name, prefixed: true)
+    Packages::GoModuleVersion.new(self, :ref, commit, ref: ref, semver: semver)
+  end
+
+  def version_by_sha(sha)
+    commit = @project.commit_by(oid: sha)
+    return unless ref
+
+    version_by_commit(commit)
+  end
+
+  def version_by_commit(commit)
+    Packages::GoModuleVersion.new(self, :commit, commit)
+  end
 end

ee/app/models/packages/go_module_version.rb

@@ -42,7 +42,14 @@ class Packages::GoModuleVersion
   end
 
   def gomod
-    @gomod ||= blob_at(@mod.path + '/go.mod')
+    @gomod ||=
+      if defined?(@blobs)
+        blob_at(@mod.path + '/go.mod')
+      elsif @mod.path.empty?
+        @mod.project.repository.blob_at(@commit.sha, 'go.mod')&.data
+      else
+        @mod.project.repository.blob_at(@commit.sha, @mod.path + '/go.mod')&.data
+      end
   end
 
   def archive
@@ -56,15 +63,12 @@ class Packages::GoModuleVersion
     end
   end
 
-  def files
-    return @files if defined?(@files)
-
-    sha = @commit.sha
-    tree = @mod.project.repository.tree(sha, @mod.path, recursive: true).entries.filter { |e| e.file? }
-    nested = tree.filter { |e| e.name == 'go.mod' && !(@mod.path == '' && e.path == 'go.mod' || e.path == @mod.path + '/go.mod') }.map { |e| e.path[0..-7] }
-    @files = tree.filter { |e| !nested.any? { |n| e.path.start_with? n } }
+  def valid?
+    @mod.path_valid?(major) && @mod.gomod_valid?(gomod)
   end
 
+  private
+
   def blob_at(path)
     return if path.nil? || path.empty?
 
@@ -73,15 +77,16 @@ class Packages::GoModuleVersion
     blobs.find { |x| x.path == path }&.data
   end
 
-  def valid?
-    @mod.path_valid?(major) && @mod.gomod_valid?(gomod)
+  def blobs
+    @blobs ||= @mod.project.repository.batch_blobs(files.map { |x| [@commit.sha, x.path] })
   end
 
-  private
-
-  def blobs
-    return @blobs if defined?(@blobs)
+  def files
+    return @files if defined?(@files)
 
-    @blobs = @mod.project.repository.batch_blobs(files.map { |x| [@commit.sha, x.path] })
+    sha = @commit.sha
+    tree = @mod.project.repository.tree(sha, @mod.path, recursive: true).entries.filter { |e| e.file? }
+    nested = tree.filter { |e| e.name == 'go.mod' && !(@mod.path == '' && e.path == 'go.mod' || e.path == @mod.path + '/go.mod') }.map { |e| e.path[0..-7] }
+    @files = tree.filter { |e| !nested.any? { |n| e.path.start_with? n } }
   end
 end

ee/lib/api/go_proxy.rb

@@ -42,7 +42,7 @@ module API
 
       def find_version
         module_version = case_decode params[:module_version]
-        ver = find_module.find_version(module_version)
+        ver = ::Packages::Go::VersionFinder.new(find_module).find(module_version)
 
         not_found! unless ver&.valid?