Serve RBS stdlib pins before the gem cache builds

lib/solargraph/doc_map.rb

@@ -231,7 +231,7 @@ def deserialize_yard_pin_cache gemspec
     end
 
     # @param gemspec [Gem::Specification]
-    # @return [void]
+    # @return [Array<Pin::Base>, nil]
     def deserialize_combined_pin_cache gemspec
       unless combined_pins_in_memory[[gemspec.name, gemspec.version]].nil?
         return combined_pins_in_memory[[gemspec.name, gemspec.version]]
@@ -270,7 +270,13 @@ def deserialize_combined_pin_cache gemspec
         combined_pins_in_memory[[gemspec.name, gemspec.version]]
       else
         logger.debug { "Pins not yet cached for #{gemspec.name}:#{gemspec.version}" }
-        nil
+        # Not stored in combined_pins_in_memory: that index is process-wide
+        # and keyed only by name and version, so a provisional set there would
+        # outlive the build that supersedes it. The gemspec stays on the
+        # uncached lists the two deserialize calls above pushed it onto.
+        fallback = rbs_map.fallback_pins
+        logger.debug { "Using fallback RBS pins for #{gemspec.name}:#{gemspec.version}" } if fallback
+        fallback
       end
     end
 

lib/solargraph/rbs_map.rb

@@ -153,6 +153,17 @@ def resolved?
       @resolved
     end
 
+    # A standalone substitute for the combined pins of this gem, for a
+    # caller that needs something before a combined cache entry exists.
+    # A base RbsMap has none to offer: a combined entry merges these pins
+    # with separately-cached YARD pins, and dropping the YARD half is not
+    # safe in general.
+    #
+    # @return [Array<Pin::Base>, nil]
+    def fallback_pins
+      nil
+    end
+
     # @return [RBS::Repository]
     def repository
       @repository ||= RBS::Repository.new(no_stdlib: false).tap do |repo|

lib/solargraph/rbs_map/stdlib_map.rb

@@ -61,6 +61,14 @@ def resolve_dependencies?
         true
       end
 
+      # Stdlib pins need no merge with YARD pins, so they stand alone
+      # as a substitute for a combined cache entry.
+      #
+      # @return [Array<Pin::Base>, nil]
+      def fallback_pins
+        pins if resolved?
+      end
+
       # @param library [String]
       # @return [StdlibMap]
       def self.load library

spec/doc_map_spec.rb

@@ -121,6 +121,33 @@
     end
   end
 
+  context 'without a combined pin cache entry for a gem' do
+    let(:pre_cache) { false }
+
+    # A version nothing will ever have cached on disk, so the read path
+    # takes the uncached branch however much of the suite ran first.
+    def uncached_gemspec name
+      Gem::Specification.new(name, '999.0.0')
+    end
+
+    it 'serves RBS stdlib pins as a fallback' do
+      pins = doc_map.send(:deserialize_combined_pin_cache, uncached_gemspec('logger'))
+      expect(pins.map(&:path)).to include('Logger#info')
+    end
+
+    it 'does not record the fallback as if it were a real build' do
+      gemspec = uncached_gemspec('logger')
+      doc_map.send(:deserialize_combined_pin_cache, gemspec)
+      expect(doc_map.combined_pins_in_memory).not_to have_key([gemspec.name, gemspec.version])
+      expect(doc_map.uncached_gemspecs).to include(gemspec)
+    end
+
+    it 'has no fallback for a gem outside the RBS stdlib' do
+      pins = doc_map.send(:deserialize_combined_pin_cache, uncached_gemspec('backport'))
+      expect(pins).to be_nil
+    end
+  end
+
   context 'with convention' do
     let(:pre_cache) { false }
 

spec/rbs_map/stdlib_map_spec.rb

@@ -62,6 +62,18 @@
     end
   end
 
+  it 'offers its pins as a fallback when resolved' do
+    map = described_class.load('yaml')
+    expect(map.fallback_pins).not_to be_empty
+    expect(map.fallback_pins).to eq(map.pins)
+  end
+
+  it 'offers no fallback pins when unresolved' do
+    map = described_class.new('not_a_stdlib_library')
+    expect(map).not_to be_resolved
+    expect(map.fallback_pins).to be_nil
+  end
+
   it 'pins are marked as coming from RBS parsing' do
     map = Solargraph::RbsMap::StdlibMap.load('yaml')
     store = Solargraph::ApiMap::Store.new(map.pins)

spec/rbs_map_spec.rb

@@ -14,6 +14,13 @@
     expect(rbs_map).not_to be_resolved
   end
 
+  it 'offers no fallback pins for a gem outside the RBS stdlib' do
+    spec = Gem::Specification.find_by_name('rbs')
+    rbs_map = described_class.from_gemspec(spec, nil, nil)
+    expect(rbs_map).to be_resolved
+    expect(rbs_map.fallback_pins).to be_nil
+  end
+
   it 'fails if it does not find data from name' do
     rbs_map = described_class.new('lskdflaksdfjl')
     expect(rbs_map.pins).to be_empty