Add hover documentation for 'case' keyword

Author: mikeygough

lib/ruby_lsp/listeners/hover.rb

@@ -8,6 +8,7 @@ class Hover
 
       ALLOWED_TARGETS = [
         Prism::CallNode,
+        Prism::CaseNode,
         Prism::ConstantReadNode,
         Prism::ConstantWriteNode,
         Prism::ConstantPathNode,
@@ -54,6 +55,7 @@ def initialize(response_builder, global_state, uri, node_context, dispatcher, so
 
         dispatcher.register(
           self,
+          :on_case_node_enter,
           :on_constant_read_node_enter,
           :on_constant_write_node_enter,
           :on_constant_path_node_enter,
@@ -97,6 +99,11 @@ def on_string_node_enter(node)
         generate_heredoc_hover(node)
       end
 
+      #: (Prism::CaseNode node) -> void
+      def on_case_node_enter(node)
+        handle_keyword_documentation(node.case_keyword)
+      end
+
       #: (Prism::InterpolatedStringNode node) -> void
       def on_interpolated_string_node_enter(node)
         generate_heredoc_hover(node)

lib/ruby_lsp/static_docs.rb

@@ -14,6 +14,7 @@ module RubyLsp
 
   # A map of keyword => short documentation to be displayed on hover or completion
   KEYWORD_DOCS = {
+    "case" => "Starts a case expression for pattern matching or multiple condition checking",
     "yield" => "Invokes the passed block with the given arguments",
   }.freeze #: Hash[String, String]
 end

static_docs/case.md

@@ -0,0 +1,99 @@
+# Case Statement
+
+In Ruby, the `case` statement provides a clean way to express conditional logic when you need to compare a value against multiple conditions. It's similar to if/else chains but often more readable and concise.
+
+```ruby
+# Basic case statement comparing a value against multiple conditions
+grade = "A"
+
+case grade
+when "A"
+  puts "Excellent!"
+when "B"
+  puts "Good job!"
+when "C"
+  puts "Fair"
+else
+  puts "Need improvement"
+end
+```
+
+The `case` statement can also work with ranges, multiple values, and even custom matching using the `===` operator.
+
+```ruby
+# Case statement with ranges and multiple conditions
+score = 85
+
+case score
+when 90..100
+  puts "A grade"
+when 80..89
+  puts "B grade"
+when 70..79
+  puts "C grade"
+else
+  puts "Need improvement"
+end
+
+# Case with multiple values in a single when clause
+day = "Saturday"
+
+case day
+when "Saturday", "Sunday"
+  puts "Weekend!"
+else
+  puts "Weekday"
+end
+```
+
+## Pattern Matching (Ruby 2.7+)
+
+Starting from Ruby 2.7, `case` statements support pattern matching, which provides powerful ways to match and destructure data.
+
+```ruby
+# Pattern matching with arrays
+data = [1, 2, 3]
+
+case data
+when [1, 2, 3]
+  puts "Exact match!"
+when [1, *rest]
+  puts "Starts with 1, followed by #{rest}"
+when Array
+  puts "Any array"
+else
+  puts "Not an array"
+end
+
+# Pattern matching with hashes (Ruby 3.0+)
+user = { name: "Alice", age: 30 }
+
+case user
+in { name: "Alice", age: }
+  puts "Alice is #{age} years old"
+in { name:, age: 20.. }
+  puts "#{name} is at least 20"
+else
+  puts "No match"
+end
+```
+
+## Case without an argument
+
+Ruby also allows `case` statements without an explicit argument, which acts like a series of if/elsif conditions.
+
+```ruby
+# Case statement without an argument
+# rubocop:disable Style/EmptyCaseCondition
+case
+when Time.now.saturday?
+  puts "It's Saturday!"
+when Time.now.sunday?
+  puts "It's Sunday!"
+else
+  puts "It's a weekday"
+end
+# rubocop:enable Style/EmptyCaseCondition
+```
+
+The case statement is particularly useful when you have multiple conditions to check against a single value, or when you want to use pattern matching to destructure complex data structures.