Class: DebugMcp::Tools::GetContext

Inherits:
MCP::Tool
  • Object
show all
Defined in:
lib/debug_mcp/tools/get_context.rb

Constant Summary collapse

TRUNCATION_PATTERN =

Pattern for detecting truncated values in debug gem output. Matches lines where the value portion ends with “…” possibly followed by closing delimiters like ], }, “, or >.

/\.\.\.[\]}"'>)]*\s*\z/
FRAMEWORK_PATH_PATTERN =

Pattern for detecting framework/gem frames in call stack.

%r{/gems/|/\.rbenv/|/\.bundle/|/vendor/bundle/|\[C\]|/ruby/\d}

Class Method Summary collapse

Class Method Details

.call(session_id: nil, server_context:) ⇒ Object 



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# File 'lib/debug_mcp/tools/get_context.rb', line 44

def call(session_id: nil, server_context:)
  client = server_context[:session_manager].client(session_id)
  client.auto_repause!

  parts = []
  total_truncated = 0

  # Show trap context warning as the first section.
  # Use cached value if available to avoid an extra round-trip.
  in_trap = if client.respond_to?(:trap_context) && !client.trap_context.nil?
    client.trap_context
  elsif client.respond_to?(:in_trap_context?)
    client.in_trap_context?
  end
  if in_trap
    parts << "=== Context: Signal Trap ===\n" \
             "Restricted: DB queries, require, autoloading, method breakpoints\n" \
             "Available: evaluate_code (simple expressions), set_breakpoint (file:line), rails_routes\n" \
             "To escape: set_breakpoint(file, line) + trigger_request"
  end

  # Collect each section independently so partial results are still useful
  variable_commands = %w[info\ locals info\ ivars]
  sections = [
    ["Current Location", "list"],
    ["Local Variables", "info locals"],
    ["Instance Variables", "info ivars"],
    ["Call Stack", "bt"],
    ["Breakpoints", "info breakpoints"],
  ]

  bt_raw = nil
  sections.each do |title, command|
    output = client.send_command(command)

    # For variable sections, detect and annotate truncated values
    if variable_commands.include?(command)
      output, truncated_count = annotate_truncated_values(output)
      if truncated_count > 0
        total_truncated += truncated_count
        title += " (#{truncated_count} truncated)"
      end
    end

    # Summarize long call stacks by collapsing framework frames
    if command == "bt"
      bt_raw = output
      output = summarize_call_stack(output)
    end

    parts << "=== #{title} ===\n#{output}"
  rescue DebugMcp::TimeoutError
    parts << "=== #{title} ===\n(timed out)"
  end

  # Annotate return events: the return value is shown in bt output (#=>)
  # and in local variables (%return). Add a note so the agent understands
  # the current line has already executed.
  if bt_raw && return_event_frame?(bt_raw)
    return_note = "=== Stop Event: Return ===\n" \
                  "The current line (=>) has ALREADY been executed. " \
                  "You are seeing the state AFTER this line ran.\n" \
                  "Return value is shown in Call Stack (#=>) and Local Variables (%return)."

    # Check if the return is due to an exception
    begin
      if (exception_info = client.check_current_exception)
        return_note += "\n\nException in scope: #{exception_info}\n" \
                       "This method/block is returning due to an exception, not a normal return."
      end
    rescue DebugMcp::Error
      # Best-effort
    end

    parts << return_note
  end

  if total_truncated > 0
    parts << "---\n#{total_truncated} variable(s) have truncated values. " \
             "Use 'inspect_object' to see full contents (e.g., inspect_object(expression: 'variable_name'))."
  else
    parts << "---\nTip: Use 'evaluate_code' or 'inspect_object' for detailed variable inspection."
  end

  if (http_note = PendingHttpHelper.pending_http_note(client))
    parts << http_note
  end

  MCP::Tool::Response.new([{ type: "text", text: parts.join("\n\n") }])
rescue DebugMcp::Error => e
  MCP::Tool::Response.new([{ type: "text", text: "Error: #{e.message}" }])
end