U622-021: Compute some completion items properties lazily

Use the newly added completionItem/resolve request to compute
the 'documentation' and 'detail' fieds of completion items lazily
when the client supports it (i.e: when a given item gets selected
in the completion window).

This makes the ALS way faster to return completion items for packages
that contain a huge number of declarations (e.g: Libadalang.Common).

VS Code already supports this lazy computation method but not other
clients.

Author: AnthonyLeonardoGracio

scripts/generate.py

@@ -257,6 +257,8 @@
      'CodeAction_Response'),
     ('textDocument/completion', 'Completion', 'TextDocumentPositionParams',
      'Completion_Response'),
+    ('completionItem/resolve', 'CompletionItemResolve', 'CompletionItem',
+     'CompletionItemResolve_Response'),
     ('textDocument/definition', 'Definition', 'DefinitionParams',
      'Location_Link_Response'),
     ('textDocument/declaration', 'Declaration', 'DeclarationParams',

source/ada/lsp-ada_completions.adb

@@ -43,6 +43,7 @@ package body LSP.Ada_Completions is
      (Context                  : LSP.Ada_Contexts.Context;
       Names                    : Completion_Maps.Map;
       Named_Notation_Threshold : Natural;
+      Compute_Doc_And_Details  : Boolean;
       Result                   : in out LSP.Messages.CompletionItem_Vector)
    is
       function Hash (Value : VSS.Strings.Virtual_String)
@@ -91,6 +92,7 @@ package body LSP.Ada_Completions is
                         BD                       => Name.P_Basic_Decl,
                         Label                    => Label,
                         Use_Snippets             => Info.Use_Snippets,
+                        Compute_Doc_And_Details  => Compute_Doc_And_Details,
                         Named_Notation_Threshold => Named_Notation_Threshold,
                         Is_Dot_Call              => Info.Is_Dot_Call,
                         Is_Visible               => Info.Is_Visible,

source/ada/lsp-ada_completions.ads

@@ -88,7 +88,15 @@ package LSP.Ada_Completions is
      (Context                  : LSP.Ada_Contexts.Context;
       Names                    : Completion_Maps.Map;
       Named_Notation_Threshold : Natural;
+      Compute_Doc_And_Details  : Boolean;
       Result                   : in out LSP.Messages.CompletionItem_Vector);
+   --  Convert all the completion Names into LSP completion items' results.
+   --  Named_Notation_Threshold defines the number of parameters/components at
+   --  which point named notation is used for subprogram/aggregate completion
+   --  snippets.
+   --  If Compute_Doc_And_Details is True, the 'detail' and 'documentation'
+   --  fields for all the resulting completion items will be computed
+   --  immediately, which might take time.
 
    generic
       with function Has_Been_Canceled return Boolean;

source/ada/lsp-ada_documents.adb

@@ -30,7 +30,6 @@ with Langkit_Support.Symbols;
 with Langkit_Support.Text;
 with Libadalang.Analysis; use Libadalang.Analysis;
 with Libadalang.Sources;
-with Libadalang.Doc_Utils;
 with Libadalang.Iterators;
 
 with VSS.String_Vectors;
@@ -1764,6 +1763,7 @@ package body LSP.Ada_Documents is
       BD                       : Libadalang.Analysis.Basic_Decl;
       Label                    : VSS.Strings.Virtual_String;
       Use_Snippets             : Boolean;
+      Compute_Doc_And_Details  : Boolean;
       Named_Notation_Threshold : Natural;
       Is_Dot_Call              : Boolean;
       Is_Visible               : Boolean;
@@ -1776,8 +1776,6 @@ package body LSP.Ada_Documents is
 
       Item           : CompletionItem;
       Subp_Spec_Node : Base_Subp_Spec;
-      Doc_Text       : VSS.Strings.Virtual_String;
-      Loc_Text       : VSS.Strings.Virtual_String;
       Min_Width      : constant Natural := Completions_Count'Img'Length - 1;
 
       function Get_Sort_text (Base_Label : LSP_String) return LSP_String;
@@ -1815,9 +1813,6 @@ package body LSP.Ada_Documents is
       Item.label := Label;
       Item.kind := (True, To_Completion_Kind
                             (LSP.Lal_Utils.Get_Decl_Kind (BD)));
-      Item.detail := (True,
-                      LSP.Types.To_LSP_String
-                        (LSP.Lal_Utils.Compute_Completion_Detail (BD)));
 
       declare
          Base_Label : constant LSP_String := LSP.Types.To_LSP_String
@@ -1836,41 +1831,39 @@ package body LSP.Ada_Documents is
          end if;
       end;
 
-      --  Property_Errors can occur when calling
-      --  Get_Documentation on unsupported docstrings, so
-      --  add an exception handler to catch them and recover.
-
-      begin
-         Doc_Text :=
-           VSS.Strings.To_Virtual_String
-             (Libadalang.Doc_Utils.Get_Documentation
-                (BD).Doc.To_String);
-
-         --  Append the declaration's location.
-         --  In addition, append the project's name if we are dealing with an
-         --  aggregate project.
-
-         Loc_Text.Append (LSP.Lal_Utils.Node_Location_Image (BD));
-
-         if not Doc_Text.Is_Empty then
-            Loc_Text.Append
-              (VSS.Strings.To_Virtual_String
-                 ((1 .. 2 => Ada.Characters.Wide_Wide_Latin_1.LF)));
-
-            Loc_Text.Append (Doc_Text);
-         end if;
-
-         Item.documentation :=
-           (Is_Set => True,
-            Value  => String_Or_MarkupContent'
-              (Is_String => True,
-               String    => Loc_Text));
-
-      exception
-         when E : Libadalang.Common.Property_Error =>
-            LSP.Common.Log (Context.Trace, E);
-            Item.documentation := (others => <>);
-      end;
+      --  Compute the 'documentation' and 'detail' fields immediately if
+      --  requested (i.e: when the client does not support lazy computation
+      --  for these fields).
+      if Compute_Doc_And_Details then
+         Item.detail :=
+           (True,
+            LSP.Types.To_LSP_String
+              (LSP.Lal_Utils.Compute_Completion_Detail (BD)));
+
+         --  Property_Errors can occur when calling
+         --  Get_Documentation on unsupported docstrings, so
+         --  add an exception handler to catch them and recover.
+         begin
+            Item.documentation :=
+              (Is_Set => True,
+               Value  => String_Or_MarkupContent'
+                 (Is_String => True,
+                  String    => LSP.Lal_Utils.Compute_Completion_Doc (BD)));
+
+         exception
+            when E : Libadalang.Common.Property_Error =>
+               LSP.Common.Log (Context.Trace, E);
+               Item.documentation := (others => <>);
+         end;
+      else
+         --  Set node's location to the 'data' field of the completion item, so
+         --  that we can retrieve it in the completionItem/resolve handler.
+         Item.data :=
+           (True,
+            (uri    => File_To_URI (BD.Unit.Get_Filename),
+             span   => LSP.Lal_Utils.To_Span (BD.Sloc_Range),
+             others => <>));
+      end if;
 
       --  Return immediately if we should not use snippets (e.g: completion for
       --  invisible symbols).

source/ada/lsp-ada_documents.ads

@@ -235,6 +235,7 @@ package LSP.Ada_Documents is
       BD                       : Libadalang.Analysis.Basic_Decl;
       Label                    : VSS.Strings.Virtual_String;
       Use_Snippets             : Boolean;
+      Compute_Doc_And_Details  : Boolean;
       Named_Notation_Threshold : Natural;
       Is_Dot_Call              : Boolean;
       Is_Visible               : Boolean;

source/ada/lsp-ada_handlers.adb

@@ -28,7 +28,6 @@ with GNAT.Strings;
 with GNATCOLL.JSON;
 with GNATCOLL.Utils;             use GNATCOLL.Utils;
 
-with VSS.String_Vectors;
 with VSS.Strings;
 with VSS.Strings.Conversions;
 with VSS.Unicode;
@@ -706,7 +705,7 @@ package body LSP.Ada_Handlers is
           workDoneProgress    => LSP.Types.None));
       Response.result.capabilities.completionProvider :=
         (True,
-         (resolveProvider     => LSP.Types.False,
+         (resolveProvider     => LSP.Types.True,
           triggerCharacters   => (True, Empty_Vector & (+".") & (+"(")),
           allCommitCharacters => (Is_Set => False),
           workDoneProgress    => LSP.Types.None));
@@ -776,6 +775,15 @@ package body LSP.Ada_Handlers is
          Self.Completion_Snippets_Enabled := True;
       end if;
 
+      if Value.capabilities.textDocument.completion.completionItem.Is_Set
+        and then Value.capabilities.textDocument.completion.
+          completionItem.Value.resolveSupport.Is_Set
+      then
+         Self.Completion_Resolve_Properties :=
+           Value.capabilities.textDocument.completion.
+             completionItem.Value.resolveSupport.Value.properties;
+      end if;
+
       if Value.capabilities.workspace.didChangeWatchedFiles
            .dynamicRegistration = True
       then
@@ -3875,8 +3883,23 @@ package body LSP.Ada_Handlers is
 
       Response : LSP.Messages.Server_Responses.Completion_Response
         (Is_Error => False);
+      Compute_Doc_And_Details : Boolean := True;
+
    begin
 
+      --  If lazy computation for the 'detail' and 'documentation' fields is
+      --  supported by the client, set the Compute_Doc_And_Details flag to
+      --  False.
+
+      if Self.Completion_Resolve_Properties.Contains
+         (VSS.Strings.Conversions.To_Virtual_String ("detail"))
+        and then
+          Self.Completion_Resolve_Properties.Contains
+            (VSS.Strings.Conversions.To_Virtual_String ("documentation"))
+      then
+         Compute_Doc_And_Details := False;
+      end if;
+
       Document.Get_Completions_At
         (Context                  => Context.all,
          Providers                => Providers,
@@ -3888,13 +3911,75 @@ package body LSP.Ada_Handlers is
         (Context                  => Context.all,
          Names                    => Names,
          Named_Notation_Threshold => Self.Named_Notation_Threshold,
+         Compute_Doc_And_Details  => Compute_Doc_And_Details,
          Result                   => Response.result.items);
 
       Response.result.isIncomplete := Names.Length >= Limit;
 
       return Response;
    end On_Completion_Request;
 
+   --------------------------------------
+   -- On_CompletionItemResolve_Request --
+   --------------------------------------
+
+   overriding function On_CompletionItemResolve_Request
+     (Self    : access Message_Handler;
+      Request : LSP.Messages.Server_Requests.CompletionItemResolve_Request)
+      return LSP.Messages.Server_Responses.CompletionItemResolve_Response
+   is
+      Item      : LSP.Messages.CompletionItem :=
+        Request.params;
+      Response  : LSP.Messages.Server_Responses.CompletionItemResolve_Response
+        (Is_Error => False);
+      C         : constant Context_Access :=
+        Self.Contexts.Get_Best_Context (Item.data.Value.uri);
+      Node      : Libadalang.Analysis.Ada_Node := Get_Node_At
+        (Self     => C.all,
+         Document => null,
+         Position => LSP.Messages.TextDocumentPositionParams'
+           (textDocument => (uri => Item.data.Value.uri),
+            position     => Item.data.Value.span.first));
+   begin
+      --  Retrieve the Basic_Decl from the completion item's SLOC
+      while not Node.Is_Null
+        and then Node.Kind not in Libadalang.Common.Ada_Basic_Decl
+      loop
+         Node := Node.Parent;
+      end loop;
+
+      --  Compute the completion item's details
+      if not Node.Is_Null then
+         declare
+            BD : constant Libadalang.Analysis.Basic_Decl :=
+              Node.As_Basic_Decl;
+         begin
+            Item.detail :=
+              (True,
+               To_LSP_String (Compute_Completion_Detail (BD)));
+
+            --  Property_Errors can occur when calling
+            --  Get_Documentation on unsupported docstrings, so
+            --  add an exception handler to catch them and recover.
+
+            Item.documentation :=
+              (Is_Set => True,
+               Value  => LSP.Messages.String_Or_MarkupContent'
+                 (Is_String => True,
+                  String    => LSP.Lal_Utils.Compute_Completion_Doc (BD)));
+
+         exception
+            when E : Libadalang.Common.Property_Error =>
+               LSP.Common.Log (C.Trace, E);
+               Item.documentation := (others => <>);
+         end;
+
+         Response.result := Item;
+      end if;
+
+      return Response;
+   end On_CompletionItemResolve_Request;
+
    ---------------------------
    -- On_Formatting_Request --
    ---------------------------

source/ada/lsp-ada_handlers.ads

@@ -20,6 +20,7 @@
 
 with Ada.Containers.Hashed_Maps;
 with Ada.Containers.Hashed_Sets;
+with VSS.String_Vectors;
 
 with GNATCOLL.VFS;    use GNATCOLL.VFS;
 with GNATCOLL.Projects;
@@ -200,6 +201,11 @@ private
       Completion_Snippets_Enabled : Boolean := False;
       --  True if the client supports completion snippets
 
+      Completion_Resolve_Properties : VSS.String_Vectors.Virtual_String_Vector;
+      --  The list of CompletionItem properties that can be resolved
+      --  lazily (i.e: when the item is selected on client-side) via
+      --  the completionItem/resolve request.
+
       Range_Formatting_Enabled : Boolean := False;
       --  True if the handler has registered rangeFormatting provider
 
@@ -272,6 +278,11 @@ private
       Request : LSP.Messages.Server_Requests.Completion_Request)
       return LSP.Messages.Server_Responses.Completion_Response;
 
+   overriding function On_CompletionItemResolve_Request
+     (Self    : access Message_Handler;
+      Request : LSP.Messages.Server_Requests.CompletionItemResolve_Request)
+      return LSP.Messages.Server_Responses.CompletionItemResolve_Response;
+
    overriding function On_Definition_Request
      (Self    : access Message_Handler;
       Request : LSP.Messages.Server_Requests.Definition_Request)

source/ada/lsp-error_decorators.adb

@@ -136,7 +136,27 @@ package body LSP.Error_Decorators is
      (Self    : access Error_Decorator;
       Request : LSP.Messages.Server_Requests.Completion_Request)
       return LSP.Messages.Server_Responses.Completion_Response
-        renames Completion_Request;
+      renames Completion_Request;
+
+   -----------------------------------
+   -- CompletionItemResolve_Request --
+   -----------------------------------
+
+   function CompletionItemResolve_Request is new Generic_Request
+     (Request    =>
+         LSP.Messages.Server_Requests.CompletionItemResolve_Request,
+      Response   =>
+         LSP.Messages.Server_Responses.CompletionItemResolve_Response,
+      Handler    =>
+         LSP.Server_Request_Handlers.Server_Request_Handler,
+      On_Request =>
+         LSP.Server_Request_Handlers.On_CompletionItemResolve_Request);
+
+   overriding function On_CompletionItemResolve_Request
+     (Self    : access Error_Decorator;
+      Request : LSP.Messages.Server_Requests.CompletionItemResolve_Request)
+      return LSP.Messages.Server_Responses.CompletionItemResolve_Response
+        renames CompletionItemResolve_Request;
 
    ---------------------------
    -- On_Declaration_Request --

source/ada/lsp-error_decorators.ads

@@ -58,6 +58,11 @@ package LSP.Error_Decorators is
       Request : LSP.Messages.Server_Requests.Completion_Request)
       return LSP.Messages.Server_Responses.Completion_Response;
 
+   overriding function On_CompletionItemResolve_Request
+     (Self    : access Error_Decorator;
+      Request : LSP.Messages.Server_Requests.CompletionItemResolve_Request)
+      return LSP.Messages.Server_Responses.CompletionItemResolve_Response;
+
    overriding function On_Definition_Request
      (Self    : access Error_Decorator;
       Request : LSP.Messages.Server_Requests.Definition_Request)