Make state type more precise

Summary:
# Context
The DAP protocol goes through several faces: first one waits for an initialization request; then for a launch/attach request; etc. On each state, we have more information than on the previous one.

The state isrepresented by the `edb_dap_server:state()` type

# Problem
The current representation loses information: we don't know which fields are mandatory in which state, etc. This makes eqwalizer less helpful and can lead to typing issues. It is also arguably harder to understand from looking at the state how it is supposed to work

# This diff
We improve the representation of the state type so that it looks closer like a state-machine, and each state has exectaly the information that is known at that point.

Doing this actually simplifies some of the handlers,

Reviewed By: TheGeorge

Differential Revision: D70342434

fbshipit-source-id: ee4899307979d4a154351c970cf29b8d7ec744d2

Author: jcpetruzza

edb/include/edb_dap.hrl

@@ -38,5 +38,5 @@
 %%%---------------------------------------------------------------------------------
 %%% Reserved for implementation-defined server-errors.
 %%%---------------------------------------------------------------------------------
--define(ERROR_SERVER_NOT_INITIALIZED, -32002).
+-define(ERROR_PRECONDITION_VIOLATION, -32002).
 -define(ERROR_NOT_SUPPORTED, -32003).

edb/src/edb_dap_internal_events.erl

@@ -65,6 +65,7 @@ nodedown_impl(State, Node, Reason) ->
                     _ -> 1
                 end,
             #{
+                state => #{state => terminating},
                 actions => [
                     {event, edb_dap_event:exited(ExitCode)},
                     {event, edb_dap_event:terminated()}

edb/src/edb_dap_request.erl

@@ -29,6 +29,11 @@
 %% Public API
 -export([dispatch/2]).
 
+%% Helpers for behaviour implementations
+-export([unexpected_request/0]).
+
+-include("edb_dap.hrl").
+
 %% ------------------------------------------------------------------
 %% Types
 %% ------------------------------------------------------------------
@@ -104,3 +109,10 @@ known_handlers() ->
         ~"threads" => edb_dap_request_threads,
         ~"variables" => edb_dap_request_variables
     }.
+
+%% ------------------------------------------------------------------
+%% Helpers for behaviour implementations
+%% ------------------------------------------------------------------
+-spec unexpected_request() -> reaction().
+unexpected_request() ->
+    #{error => {user_error, ?ERROR_PRECONDITION_VIOLATION, ~"Request sent when it was not expected"}}.

edb/src/edb_dap_request_continue.erl

@@ -58,7 +58,9 @@ parse_arguments(Args) ->
 -spec handle(State, Args) -> edb_dap_request:reaction(response_body()) when
     State :: edb_dap_server:state(),
     Args :: arguments().
-handle(_State, _Args) ->
+handle(#{state := attached}, _Args) ->
     edb_dap_id_mappings:reset(),
     {ok, _} = edb:continue(),
-    #{response => #{success => true, body => #{allThreadsContinued => true}}}.
+    #{response => #{success => true, body => #{allThreadsContinued => true}}};
+handle(_UnexpectedState, _) ->
+    edb_dap_request:unexpected_request().

edb/src/edb_dap_request_initialize.erl

@@ -24,8 +24,6 @@
 
 -export([parse_arguments/1, handle/2]).
 
--include("edb_dap.hrl").
-
 %% ------------------------------------------------------------------
 %% Types
 %% ------------------------------------------------------------------
@@ -155,14 +153,14 @@ parse_arguments(Args) ->
 -spec handle(State, Args) -> edb_dap_request:reaction(capabilities()) when
     State :: edb_dap_server:state(),
     Args :: arguments().
-handle(State = #{state := started}, _Args) ->
+handle(#{state := started}, ClientInfo) ->
     Capabilities = capabilities(),
     #{
         response => #{success => true, body => Capabilities},
-        state => State#{state => initialized}
+        state => #{state => initialized, client_info => ClientInfo}
     };
-handle(_InitializedState, _Args) ->
-    #{error => {user_error, ?JSON_RPC_ERROR_INVALID_REQUEST, ~"Already initialized"}}.
+handle(_InvalidState, _Args) ->
+    edb_dap_request:unexpected_request().
 
 %% ------------------------------------------------------------------
 %% Helpers

edb/src/edb_dap_request_launch.erl

@@ -79,7 +79,7 @@ parse_arguments(Args) ->
 -spec handle(State, Args) -> edb_dap_request:reaction() when
     State :: edb_dap_server:state(),
     Args :: arguments().
-handle(State0, Args) ->
+handle(State0 = #{state := initialized}, Args) ->
     #{launchCommand := LaunchCommand, targetNode := TargetNode} = Args,
     #{cwd := Cwd, command := Command} = LaunchCommand,
     AttachTimeoutInSecs = maps:get(timeout, Args, ?DEFAULT_ATTACH_TIMEOUT_IN_SECS),
@@ -94,6 +94,7 @@ handle(State0, Args) ->
         env => Env#{~"ERL_FLAGS" => ?ERL_FLAGS}
     }),
     State1 = State0#{
+        state => launching,
         context => #{
             target_node => TargetNode,
             attach_timeout => AttachTimeoutInSecs,
@@ -106,7 +107,9 @@ handle(State0, Args) ->
         response => #{success => true},
         actions => [{reverse_request, RunInTerminalRequest}],
         state => State1
-    }.
+    };
+handle(_InvalidState, _Args) ->
+    edb_dap_request:unexpected_request().
 
 %% ------------------------------------------------------------------
 %% Helpers

edb/src/edb_dap_request_next.erl

@@ -24,7 +24,7 @@
 
 -export([parse_arguments/1, handle/2]).
 
--export([stepper/2]).
+-export([stepper/3]).
 
 -include_lib("kernel/include/logger.hrl").
 -include("edb_dap.hrl").
@@ -59,16 +59,17 @@ parse_arguments(Args) ->
 -spec handle(State, Args) -> edb_dap_request:reaction() when
     State :: edb_dap_server:state(),
     Args :: arguments().
-handle(_State, #{threadId := ThreadId}) ->
-    stepper(ThreadId, 'step-over').
+handle(State, #{threadId := ThreadId}) ->
+    stepper(State, ThreadId, 'step-over').
 
 %% ------------------------------------------------------------------
 %% Generic stepping implementation
 %% ------------------------------------------------------------------
--spec stepper(ThreadId, StepType) -> edb_dap_request:reaction() when
+-spec stepper(State, ThreadId, StepType) -> edb_dap_request:reaction() when
+    State :: edb_dap_server:state(),
     ThreadId :: edb_dap:thread_id(),
     StepType :: 'step-over' | 'step-out'.
-stepper(ThreadId, StepType) ->
+stepper(#{state := attached}, ThreadId, StepType) ->
     StepFun =
         case StepType of
             'step-over' -> fun edb:step_over/1;
@@ -90,4 +91,6 @@ stepper(ThreadId, StepType) ->
         {error, not_found} ->
             ?LOG_WARNING("Cannot find pid for thread id ~p", [ThreadId]),
             throw(~"Unknown threadId")
-    end.
+    end;
+stepper(_UnexpectedState, _, _) ->
+    edb_dap_request:unexpected_request().

edb/src/edb_dap_request_pause.erl

@@ -46,6 +46,8 @@ parse_arguments(Args) ->
 -spec handle(State, Args) -> edb_dap_request:reaction() when
     State :: edb_dap_server:state(),
     Args :: arguments().
-handle(_State, _Args) ->
+handle(#{state := attached}, _Args) ->
     ok = edb:pause(),
-    #{response => #{success => true}}.
+    #{response => #{success => true}};
+handle(_UnexpectedState, _) ->
+    edb_dap_request:unexpected_request().

edb/src/edb_dap_request_scopes.erl

@@ -100,7 +100,7 @@ parse_arguments(Args) ->
 -spec handle(State, Args) -> edb_dap_request:reaction(response_body()) when
     State :: edb_dap_server:state(),
     Args :: arguments().
-handle(State, #{frameId := FrameId}) ->
+handle(#{state := attached, context := Context}, #{frameId := FrameId}) ->
     {ok, #{pid := Pid, frame_no := FrameNo}} = edb_dap_id_mappings:frame_id_to_pid_frame(FrameId),
     VariablesScopes =
         case edb:stack_frame_vars(Pid, FrameNo, _MaxTermSize = 1) of
@@ -129,7 +129,7 @@ handle(State, #{frameId := FrameId}) ->
             _ ->
                 []
         end,
-    #{context := #{target_node := #{name := Node}}} = State,
+    #{target_node := #{name := Node}} = Context,
     MessagesScopes =
         % elp:ignore W0014 (cross_node_eval)
         case erpc:call(Node, erlang, process_info, [Pid, message_queue_len]) of
@@ -153,4 +153,6 @@ handle(State, #{frameId := FrameId}) ->
                 scopes => MessagesScopes ++ VariablesScopes
             }
         }
-    }.
+    };
+handle(_UnexpectedState, _) ->
+    edb_dap_request:unexpected_request().

edb/src/edb_dap_request_set_breakpoints.erl

@@ -149,11 +149,11 @@ parse_arguments(Args) ->
 -spec handle(State, Args) -> edb_dap_request:reaction(breakpoints()) when
     State :: edb_dap_server:state(),
     Args :: arguments().
-handle(State, Args = #{source := #{path := Path}}) ->
+handle(#{state := attached, context := Context}, Args = #{source := #{path := Path}}) ->
     Module = binary_to_atom(filename:basename(Path, ".erl")),
 
     % TODO(T202772655): Remove once edb:set_breakpoint/2 takes care of auto-loading modules
-    #{context := #{target_node := #{name := Node}}} = State,
+    #{target_node := #{name := Node}} = Context,
     % elp:ignore W0014 (cross_node_eval)
     erpc:call(Node, code, ensure_loaded, [Module]),
 
@@ -176,4 +176,6 @@ handle(State, Args = #{source := #{path := Path}}) ->
         LineResults
     ),
     Body = #{breakpoints => Breakpoints},
-    #{response => #{success => true, body => Body}}.
+    #{response => #{success => true, body => Body}};
+handle(_UnexpectedState, _) ->
+    edb_dap_request:unexpected_request().