Make pipe completion work reliably across submodules.

Before this, a type path of non-zero length was assumed to come from the compiler, otherwise the path of the completion environment was taken verbatim.

Neither case is correct.

Now there's a single case, where one takes into account 2 inputs:
- the current environment which gives context to the type path
-  the type path, which is interpreted as starting within that environment

Since submodules can refer to types into other submodules, the path needs to be resolved to determine the actual path starting from the root of the file. This requires keeping track of where a module is defined. It could be defined in the current env, or in a parent one. The current env is walked backwards toward the root until the required module is found, and the resulting paths combined.

Author: cristianoc

Diff for: CHANGELOG.md

@@ -20,6 +20,7 @@
 - Accept both `@ns.doc` and the new `@res.doc` for the internal representation of doc comments. And both `@ns.optional` and `@res.optional` for the optional fields. https://github.com/rescript-lang/rescript-vscode/pull/642
 - Make pipe completion work more reliably after function calls. https://github.com/rescript-lang/rescript-vscode/pull/656
 - Make pipe completion work in pipe chains, not just on the first pipe. https://github.com/rescript-lang/rescript-vscode/pull/656
+- Make pipe completion work reliably when the path resolution needs to traverse submodules
 
 #### :bug: Bug Fix
 

Diff for: analysis/src/CompletionBackEnd.ml

@@ -1348,21 +1348,21 @@ let rec getCompletionsForContextPath ~package ~opens ~rawOpens ~allFiles ~pos
           | Some path -> Some path
           | None -> (
             match expandPath typePath with
-            | _ :: rest when rest <> [] ->
-              (* Assume a non-empty type path is coming from the compiler and
-                 can be used as-is. *)
-              Some (List.rev rest)
-            | _ ->
-              (* Get the path from the comletion environment *)
-              let path = envFromCompletionItem.path in
-              if path = [] then None
+            | _ :: pathRev ->
+              (* type path is relative to the completion environment
+                 express it from the root of the file *)
+              let pathFromEnv_ =
+                QueryEnv.pathFromEnv envFromCompletionItem (List.rev pathRev)
+              in
+              if pathFromEnv_ = [] then None
               else
                 let pathFromEnv =
                   if env.file.moduleName = envFromCompletionItem.file.moduleName
-                  then path
-                  else envFromCompletionItem.file.moduleName :: path
+                  then pathFromEnv_
+                  else envFromCompletionItem.file.moduleName :: pathFromEnv_
                 in
-                Some pathFromEnv))
+                Some pathFromEnv
+            | _ -> None))
         | None -> None
       in
       match completionPath with

Diff for: analysis/src/SharedTypes.ml

@@ -238,15 +238,45 @@ module File = struct
 end
 
 module QueryEnv : sig
-  type t = private {file: File.t; exported: Exported.t; path: path}
+  type t = private {
+    file: File.t;
+    exported: Exported.t;
+    pathRev: path;
+    parent: t option;
+  }
   val fromFile : File.t -> t
   val enterStructure : t -> Module.structure -> t
+
+  (* Express a path starting from the module represented by the env.
+     E.g. the env is at A.B.C and the path is D.
+     The result is A.B.C.D if D is inside C.
+     Or A.B.D or A.D or D if it's in one of its parents. *)
+  val pathFromEnv : t -> path -> path
 end = struct
-  type t = {file: File.t; exported: Exported.t; path: path}
+  type t = {file: File.t; exported: Exported.t; pathRev: path; parent: t option}
+
+  let fromFile (file : File.t) =
+    {file; exported = file.structure.exported; pathRev = []; parent = None}
+
+  (* Prune a path and find a parent environment that contains the module name *)
+  let rec prunePath pathRev env name =
+    if Exported.find env.exported Module name <> None then pathRev
+    else
+      match (pathRev, env.parent) with
+      | _ :: rest, Some env -> prunePath rest env name
+      | _ -> []
+
+  let pathFromEnv env path =
+    match path with
+    | [] -> env.pathRev |> List.rev
+    | name :: _ ->
+      let prunedPathRev = prunePath env.pathRev env name in
+      List.rev_append prunedPathRev path
 
-  let fromFile file = {file; exported = file.structure.exported; path = []}
   let enterStructure env (structure : Module.structure) =
-    {env with exported = structure.exported; path = structure.name :: env.path}
+    let name = structure.name in
+    let pathRev = name :: prunePath env.pathRev env name in
+    {env with exported = structure.exported; pathRev; parent = Some env}
 end
 
 module Completion = struct

Diff for: analysis/tests/src/CompletionPipeSubmodules.res

@@ -0,0 +1,45 @@
+module A = {
+  module B1 = {
+    type b1 = B1
+    let xx = B1
+  }
+  module B2 = {
+    let yy = 20
+  }
+  type t = {v: B1.b1}
+  let x = {v: B1.B1}
+}
+
+// let _ = A.B1.xx->
+//                  ^com
+// b1 seen from B1 is A.B1.b1
+
+// let _ = A.x.v->
+//                ^com
+// B1.b1 seen from A  is A.B1.b1
+
+module C = {
+  type t = C
+}
+
+module D = {
+  module C2 = {
+    type t2 = C2
+  }
+
+  type d = {v: C.t, v2: C2.t2}
+  let d = {v: C.C, v2: C2.C2}
+}
+
+module E = {
+  type e = {v: D.d}
+  let e = {v: D.d}
+}
+
+// let _ = E.e.v.v->
+//                  ^com
+// C.t seen from D is C.t
+
+// let _ = E.e.v.v2->
+//                   ^com
+// C2.t2 seen from D is D.C2.t2

Diff for: analysis/tests/src/expected/CompletionPipeSubmodules.res.txt

@@ -0,0 +1,56 @@
+Complete src/CompletionPipeSubmodules.res 12:20
+posCursor:[12:20] posNoWhite:[12:19] Found expr:[12:11->20:8]
+Completable: Cpath Value[A, B1, xx]->
+[{
+    "label": "A.B1.xx",
+    "kind": 12,
+    "tags": [],
+    "detail": "b1",
+    "documentation": null
+  }, {
+    "label": "A.B1.B1",
+    "kind": 4,
+    "tags": [],
+    "detail": "B1\n\ntype b1 = B1",
+    "documentation": null
+  }]
+
+Complete src/CompletionPipeSubmodules.res 16:18
+posCursor:[16:18] posNoWhite:[16:17] Found expr:[16:11->20:8]
+Completable: Cpath Value[A, x].v->
+[{
+    "label": "A.B1.xx",
+    "kind": 12,
+    "tags": [],
+    "detail": "b1",
+    "documentation": null
+  }, {
+    "label": "A.B1.B1",
+    "kind": 4,
+    "tags": [],
+    "detail": "B1\n\ntype b1 = B1",
+    "documentation": null
+  }]
+
+Complete src/CompletionPipeSubmodules.res 38:20
+posCursor:[38:20] posNoWhite:[38:19] Found expr:[38:11->0:-1]
+Completable: Cpath Value[E, e].v.v->
+[{
+    "label": "C.C",
+    "kind": 4,
+    "tags": [],
+    "detail": "C\n\ntype t = C",
+    "documentation": null
+  }]
+
+Complete src/CompletionPipeSubmodules.res 42:21
+posCursor:[42:21] posNoWhite:[42:20] Found expr:[42:11->0:-1]
+Completable: Cpath Value[E, e].v.v2->
+[{
+    "label": "D.C2.C2",
+    "kind": 4,
+    "tags": [],
+    "detail": "C2\n\ntype t2 = C2",
+    "documentation": null
+  }]
+