Milestone to graduate stringio from core.

lib/rbs/environment_loader.rb

@@ -113,6 +113,11 @@ def load(env:)
       # @type var loaded: Array[[AST::Declarations::t, Pathname, source]]
       loaded = []
 
+      # For migrating stringio to stdlib
+      if @core_root && libs.none? { |lib| lib.name == 'stringio' }
+        add(library: 'stringio', version: nil)
+      end
+
       each_signature do |source, path, buffer, decls, dirs|
         decls.each do |decl|
           loaded << [decl, path, source]

stdlib/cgi/0/manifest.yaml

@@ -1,2 +1,3 @@
 dependencies:
   - name: tempfile
+  - name: stringio

stdlib/csv/0/manifest.yaml

@@ -1,2 +1,3 @@
 dependencies:
   - name: forwardable
+  - name: stringio

stdlib/open-uri/0/manifest.yaml

@@ -1,3 +1,4 @@
 dependencies:
   - name: tempfile
   - name: uri
+  - name: stringio

test/rbs/collection/config_test.rb

@@ -340,6 +340,10 @@ def test_generate_lock_from_stdlib
             version: "0"
             source:
               type: stdlib
+          - name: stringio
+            version: "0"
+            source:
+              type: stdlib
       YAML
     end
   end

test/rbs/environment_loader_test.rb

@@ -40,7 +40,8 @@ def test_loading_empty
 
     env = Environment.new
     loaded = loader.load(env: env)
-
+    _, _, lib = loaded.delete_if { |_, _, lib| lib.name == "stringio" }
+    assert lib
     assert loaded.all? {|_, _, path_type| path_type == :core }
   end
 
@@ -242,7 +243,7 @@ def test_loading_from_rbs_collection
 
   def test_loading_from_rbs_collection__gem_version_mismatch
     omit "Test gem `rbs-amber` is unavailable" unless has_gem?("rbs-amber")
-    
+
     mktmpdir do |path|
       lockfile_path = path.join('rbs_collection.lock.yaml')
       lockfile_path.write(<<~YAML)