Add 'else' keyword

Author: mikeygough

lib/ruby_lsp/listeners/hover.rb

@@ -16,6 +16,7 @@ class Hover
         Prism::ConstantPathNode,
         Prism::DefNode,
         Prism::DefinedNode,
+        Prism::ElseNode,
         Prism::GlobalVariableAndWriteNode,
         Prism::GlobalVariableOperatorWriteNode,
         Prism::GlobalVariableOrWriteNode,
@@ -68,6 +69,7 @@ def initialize(response_builder, global_state, uri, node_context, dispatcher, so
           :on_call_node_enter,
           :on_def_node_enter,
           :on_defined_node_enter,
+          :on_else_node_enter,
           :on_global_variable_and_write_node_enter,
           :on_global_variable_operator_write_node_enter,
           :on_global_variable_or_write_node_enter,
@@ -132,6 +134,11 @@ def on_defined_node_enter(node)
         handle_keyword_documentation(node.keyword)
       end
 
+      #: (Prism::ElseNode node) -> void
+      def on_else_node_enter(node)
+        handle_keyword_documentation(node.else_keyword)
+      end
+
       #: (Prism::InterpolatedStringNode node) -> void
       def on_interpolated_string_node_enter(node)
         generate_heredoc_hover(node)

lib/ruby_lsp/static_docs.rb

@@ -19,6 +19,7 @@ module RubyLsp
     "class" => "Defines a class and its methods",
     "def" => "Defines a method",
     "defined?" => "Checks if a constant or method is defined",
+    "else" => "Executes the code in the else block if the condition is false",
     "yield" => "Invokes the passed block with the given arguments",
   }.freeze #: Hash[String, String]
 end

static_docs/else.md

@@ -0,0 +1,106 @@
+# Else
+
+In Ruby, the `else` keyword is used to define an alternative execution path in conditional statements. It works with `if`, `unless`, `case`, and `begin/rescue` blocks to handle cases when the primary conditions are not met.
+
+```ruby
+# Basic else usage with if
+status = "error"
+
+if status == "success"
+  puts "Operation completed"
+else
+  puts "Operation failed"
+end
+# Output:
+# Operation failed
+```
+
+The `else` clause can be used with various conditional structures in Ruby.
+
+```ruby
+# With unless
+temperature = 25
+
+unless temperature < 20
+  puts "It's warm"
+else
+  puts "It's cool"
+end
+# Output:
+# It's warm
+
+# With case statement
+grade = "B"
+
+case grade
+when "A"
+  puts "Excellent!"
+when "B"
+  puts "Good job!"
+else
+  puts "Keep working hard!"
+end
+# Output:
+# Good job!
+```
+
+## Error Handling
+
+The `else` keyword is commonly used with `begin/rescue` blocks for error handling.
+
+```ruby
+begin
+  result = 10 / 0
+rescue ZeroDivisionError
+  puts "Cannot divide by zero"
+else
+  # Executes only if no error was raised
+  puts "Result: #{result}"
+ensure
+  puts "Calculation attempted"
+end
+# Output:
+# Cannot divide by zero
+# Calculation attempted
+```
+
+## Ternary Operator Alternative
+
+For simple conditions, Ruby provides a ternary operator as a concise alternative to `if/else`.
+
+```ruby
+def check_temperature(temp)
+  temp >= 25 ? "It's hot" : "It's cool"
+end
+
+puts check_temperature(30) # Output: It's hot
+puts check_temperature(20) # Output: It's cool
+
+# Compared to if/else
+def check_temperature_verbose(temp)
+  if temp >= 25
+    "It's hot"
+  else
+    "It's cool"
+  end
+end
+```
+
+## Method Return Values
+
+The `else` clause affects the return value in conditional expressions.
+
+```ruby
+def process_number(num)
+  if num.even?
+    "Even number: #{num}"
+  else
+    "Odd number: #{num}"
+  end
+end
+
+puts process_number(42)  # Output: Even number: 42
+puts process_number(37)  # Output: Odd number: 37
+```
+
+The `else` keyword is fundamental to control flow in Ruby, providing clear paths for alternate execution when conditions are not met.