Add UnannotatedEmptyCollection diagnostic

dak2 · Nov 19, 2024 · fd91c3f · fd91c3f
1 parent 271802b
commit fd91c3f
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Showing 5 changed files with 87 additions and 4 deletions.
diff --git a/lib/steep/diagnostic/ruby.rb b/lib/steep/diagnostic/ruby.rb
@@ -917,6 +917,13 @@ def header_line
         end
       end
 
+      class UnannotatedEmptyCollection < Base
+        def header_line
+          node or raise
+          "Empty #{node.type} doesn't have type annotation"
+        end
+      end
+
       ALL = ObjectSpace.each_object(Class).with_object([]) do |klass, array|
         if klass < Base
           array << klass
@@ -963,6 +970,7 @@ def self.default
             SetterReturnTypeMismatch => :information,
             SyntaxError => :hint,
             TypeArgumentMismatchError => :hint,
+            UnannotatedEmptyCollection => :warning,
             UnexpectedBlockGiven => :warning,
             UnexpectedDynamicMethod => :hint,
             UnexpectedError => :hint,
@@ -1019,6 +1027,7 @@ def self.strict
             SetterReturnTypeMismatch => :error,
             SyntaxError => :hint,
             TypeArgumentMismatchError => :error,
+            UnannotatedEmptyCollection => :error,
             UnexpectedBlockGiven => :error,
             UnexpectedDynamicMethod => :information,
             UnexpectedError => :information,
@@ -1075,6 +1084,7 @@ def self.lenient
             SetterReturnTypeMismatch => nil,
             SyntaxError => :hint,
             TypeArgumentMismatchError => nil,
+            UnannotatedEmptyCollection => :hint,
             UnexpectedBlockGiven => :hint,
             UnexpectedDynamicMethod => nil,
             UnexpectedError => :hint,

diff --git a/lib/steep/type_construction.rb b/lib/steep/type_construction.rb
@@ -1436,7 +1436,7 @@ def synthesize(node, hint: nil, condition: false)
                 # ok
               else
                 unless hint == pair.type
-                  pair.constr.typing.add_error Diagnostic::Ruby::FallbackAny.new(node: node)
+                  pair.constr.typing.add_error Diagnostic::Ruby::UnannotatedEmptyCollection.new(node: node)
                 end
               end
             end
@@ -1704,7 +1704,7 @@ def synthesize(node, hint: nil, condition: false)
                   add_typing node, type: array
                 end
               else
-                typing.add_error Diagnostic::Ruby::FallbackAny.new(node: node)
+                typing.add_error Diagnostic::Ruby::UnannotatedEmptyCollection.new(node: node)
                 add_typing node, type: AST::Builtin::Array.instance_type(AST::Builtin.any_type)
               end
             else

diff --git a/sig/steep/diagnostic/ruby.rbs b/sig/steep/diagnostic/ruby.rbs
@@ -626,6 +626,33 @@ module Steep
         def header_line: () -> String
       end
 
+      # An empty array/hash has no type assertion
+      #
+      # They are typed as `Array[untyped]` or `Hash[untyped, untyped]`,
+      # which allows any element to be added.
+      #
+      # ```rb
+      # a = []
+      # b = {}
+      #
+      # a << 1
+      # a << ""
+      # ```
+      #
+      # Add type annotation to make your assumption explicit.
+      #
+      # ```rb
+      # a = [] #: Array[Integer]
+      # b = {} #: untyped
+      #
+      # a << 1
+      # a << ""     # => Type error
+      # ```
+      #
+      class UnannotatedEmptyCollection < Base
+        def header_line: () -> String
+      end
+
       ALL: Array[singleton(Base)]
 
       type template = Hash[singleton(Base), LSPFormatter::severity?]

diff --git a/test/type_check_test.rb b/test/type_check_test.rb
@@ -2483,4 +2483,50 @@ def test_untyped_hash
       YAML
     )
   end
+
+  def test_empty_collection
+    run_type_check_test(
+      signatures: {
+        "a.rbs" => <<~RBS
+        RBS
+      },
+      code: {
+        "a.rb" => <<~RUBY
+          a = []
+          b = {}
+
+          x = [] #: Array[String]
+          y = {} #: Hash[String, untyped]
+
+          t = [] #: untyped
+          s = {} #: untyped
+        RUBY
+      },
+      expectations: <<~YAML
+      ---
+      - file: a.rb
+        diagnostics:
+        - range:
+            start:
+              line: 1
+              character: 4
+            end:
+              line: 1
+              character: 6
+          severity: ERROR
+          message: Empty array doesn't have type annotation
+          code: Ruby::UnannotatedEmptyCollection
+        - range:
+            start:
+              line: 2
+              character: 4
+            end:
+              line: 2
+              character: 6
+          severity: ERROR
+          message: Empty hash doesn't have type annotation
+          code: Ruby::UnannotatedEmptyCollection
+      YAML
+    )
+  end
 end
diff --git a/test/type_construction_test.rb b/test/type_construction_test.rb
@@ -877,7 +877,7 @@ def foo: (Integer) -> void
 
         assert_typing_error(typing, size: 2) do |errors|
           errors[0].tap do |error|
-            assert_instance_of Diagnostic::Ruby::FallbackAny, error
+            assert_instance_of Diagnostic::Ruby::UnannotatedEmptyCollection, error
           end
 
           errors[1].tap do |error|
@@ -4369,7 +4369,7 @@ def test_empty_array_is_error
 
         assert_equal 2, typing.errors.size
         assert_all typing.errors do |error|
-          error.is_a?(Diagnostic::Ruby::FallbackAny)
+          error.is_a?(Diagnostic::Ruby::UnannotatedEmptyCollection)
         end
       end
     end