Merge pull request #272 from rescript-association/playground-type-hover

Playground type hover

Author: ryyppy

src/Playground.js

@@ -1526,10 +1526,33 @@ let default = () => {
   | _ => []
   }
 
+  let cmHoverHints = switch compilerState {
+  | Ready({result: FinalResult.Comp(Success({type_hints}))}) =>
+    Js.Array2.map(type_hints, hint => {
+      switch hint {
+      | TypeDeclaration({start, end, hint})
+      | Binding({start, end, hint})
+      | CoreType({start, end, hint})
+      | Expression({start, end, hint}) => {
+          CodeMirror.HoverHint.start: {
+            line: start.line,
+            col: start.col,
+          },
+          end: {
+            line: end.line,
+            col: end.col,
+          },
+          hint: hint,
+        }
+      }
+    })
+  | _ => []
+  }
+
   let mode = switch compilerState {
-    | Ready({ targetLang: Reason }) => "reason"
-    | Ready({ targetLang: Res }) => "rescript"
-    | _ => "rescript"
+  | Ready({targetLang: Reason}) => "reason"
+  | Ready({targetLang: Res}) => "rescript"
+  | _ => "rescript"
   }
 
   <>
@@ -1559,6 +1582,7 @@ let default = () => {
                   minHeight="calc(100vh - 10rem)"
                   maxHeight="calc(100vh - 10rem)"
                   mode
+                  hoverHints=cmHoverHints
                   errors=cmErrors
                   value={editorCode.current}
                   onChange={value => {

src/Playground.res

@@ -178,10 +178,55 @@ module WarningFlag = {
   }
 }
 
+module TypeHint = {
+  type position = {
+    line: int,
+    col: int,
+  }
+
+  type data = {
+    start: position,
+    end: position,
+    hint: string,
+  }
+
+  type t =
+    | TypeDeclaration(data)
+    | Expression(data)
+    | Binding(data)
+    | CoreType(data)
+
+  let decodePosition = json => {
+    open Json.Decode
+    {
+      line: field("line", int, json),
+      col: field("col", int, json),
+    }
+  }
+
+  let decode = (json): t => {
+    open Json.Decode
+    let data = {
+      start: field("start", decodePosition, json),
+      end: field("end", decodePosition, json),
+      hint: field("hint", string, json),
+    }
+
+    switch field("kind", string, json) {
+    | "expression" => Expression(data)
+    | "type_declaration" => TypeDeclaration(data)
+    | "binding" => Binding(data)
+    | "core_type" => CoreType(data)
+    | other => raise(DecodeError(`Unknown kind "${other}" type hint`))
+    }
+  }
+}
+
 module CompileSuccess = {
   type t = {
     js_code: string,
     warnings: array<Warning.t>,
+    type_hints: array<TypeHint.t>,
     time: float, // total compilation time
   }
 
@@ -190,6 +235,7 @@ module CompileSuccess = {
     {
       js_code: field("js_code", string, json),
       warnings: field("warnings", array(Warning.decode), json),
+      type_hints: withDefault([], field("type_hints", array(TypeHint.decode)), json),
       time: time,
     }
   }