Add 'rescue' keyword

Author: mikeygough

lib/ruby_lsp/listeners/hover.rb

@@ -33,6 +33,7 @@ class Hover
         Prism::InstanceVariableWriteNode,
         Prism::ModuleNode,
         Prism::NextNode,
+        Prism::RescueNode,
         Prism::SymbolNode,
         Prism::StringNode,
         Prism::InterpolatedStringNode,
@@ -90,6 +91,7 @@ def initialize(response_builder, global_state, uri, node_context, dispatcher, so
           :on_instance_variable_target_node_enter,
           :on_module_node_enter,
           :on_next_node_enter,
+          :on_rescue_node_enter,
           :on_super_node_enter,
           :on_forwarding_super_node_enter,
           :on_string_node_enter,
@@ -167,6 +169,11 @@ def on_next_node_enter(node)
         handle_keyword_documentation(node.keyword)
       end
 
+      #: (Prism::RescueNode node) -> void
+      def on_rescue_node_enter(node)
+        handle_keyword_documentation(node.keyword)
+      end
+
       #: (Prism::InterpolatedStringNode node) -> void
       def on_interpolated_string_node_enter(node)
         generate_heredoc_hover(node)

lib/ruby_lsp/static_docs.rb

@@ -24,6 +24,7 @@ module RubyLsp
     "for" => "Iterates over a collection of elements",
     "module" => "Defines a module",
     "next" => "Skips the rest of the current iteration and moves to the next iteration of a loop or block",
+    "rescue" => "Handles exceptions that occur in the code block",
     "yield" => "Invokes the passed block with the given arguments",
   }.freeze #: Hash[String, String]
 end

static_docs/rescue.md

@@ -0,0 +1,93 @@
+# Rescue
+
+In Ruby, `rescue` is used to handle exceptions that occur during program execution. It allows you to catch and handle errors gracefully, preventing your program from crashing.
+
+```ruby
+# Basic rescue usage
+begin
+  # Code that might raise an exception
+  result = 10 / 0
+rescue
+  puts "An error occurred!"
+end
+```
+
+You can specify which type of exception to rescue, and capture the exception object for inspection:
+
+```ruby
+begin
+  # Attempting to divide by zero raises a ZeroDivisionError
+  result = 10 / 0
+rescue ZeroDivisionError => e
+  puts "Cannot divide by zero: #{e.message}"
+end
+```
+
+Multiple rescue clauses can be used to handle different types of exceptions:
+
+```ruby
+begin
+  # Code that might raise different types of exceptions
+  JSON.parse(invalid_json)
+rescue JSON::ParserError => e
+  puts "Invalid JSON format: #{e.message}"
+rescue StandardError => e
+  puts "Some other error occurred: #{e.message}"
+end
+```
+
+## Inline rescue
+
+Ruby also supports inline rescue clauses for simple error handling:
+
+```ruby
+# If the division fails, return nil instead
+result = 10 / params[:divisor].to_i rescue nil
+
+# This is equivalent to:
+result = begin
+  10 / params[:divisor].to_i
+rescue
+  nil
+end
+```
+
+## Ensure and else clauses
+
+The `rescue` keyword can be used with `ensure` and `else` clauses:
+
+```ruby
+begin
+  # Attempt some operation
+  file = File.open("example.txt")
+  content = file.read
+rescue Errno::ENOENT => e
+  puts "Could not find the file: #{e.message}"
+else
+  # This block only executes if no exception was raised
+  puts "Successfully read #{content.length} bytes"
+ensure
+  # This block always executes, whether an exception occurred or not
+  file&.close
+end
+```
+
+## Method-level rescue
+
+You can also use `rescue` at the method level without an explicit `begin` block:
+
+```ruby
+def process_file(path)
+  File.read(path)
+rescue Errno::ENOENT
+  puts "File not found"
+rescue Errno::EACCES
+  puts "Permission denied"
+end
+```
+
+When rescuing exceptions, it's important to:
+- Only rescue specific exceptions you can handle
+- Avoid rescuing `Exception` as it captures all exceptions, including system ones
+- Use `ensure` for cleanup code that must always run
+- Keep the rescue block focused on error handling logic 

test/requests/hover_expectations_test.rb

@@ -994,6 +994,16 @@ module MyModule
         RUBY
         position: { line: 1, character: 2 },
       },
+      "rescue" => {
+        source: <<~RUBY,
+          begin
+            true
+          rescue
+            false
+          end
+        RUBY
+        position: { line: 2, character: 2 },
+      },
     }
 
     test_cases.each do |keyword, config|