Fix completion on first character (#909)

src/FsAutoComplete.Core/Lexer.fs

@@ -22,9 +22,9 @@ type LexerSymbol =
 [<RequireQualifiedAccess>]
 type SymbolLookupKind =
     | Fuzzy
-    | ByRightColumn
     | ByLongIdent
     | Simple
+    | ForCompletion
 
 type private DraftToken =
     { Kind: SymbolKind
@@ -135,8 +135,8 @@ module Lexer =
             match lookupKind with
             | SymbolLookupKind.Simple | SymbolLookupKind.Fuzzy ->
                 tokens |> List.filter (fun x -> x.Token.LeftColumn <= col && x.RightColumn + 1 >= col)
-            | SymbolLookupKind.ByRightColumn ->
-                tokens |> List.filter (fun x -> x.RightColumn = col)
+            | SymbolLookupKind.ForCompletion ->
+                tokens |> List.filter (fun x -> x.Token.LeftColumn <= col && x.RightColumn >= col)
             | SymbolLookupKind.ByLongIdent ->
                 tokens |> List.filter (fun x -> x.Token.LeftColumn <= col)
 
@@ -172,8 +172,7 @@ module Lexer =
                       LeftColumn = leftCol
                       RightColumn = first.RightColumn + 1
                       Text = lineStr.[leftCol..first.RightColumn] })
-        | SymbolLookupKind.Fuzzy
-        | SymbolLookupKind.ByRightColumn ->
+        | SymbolLookupKind.Fuzzy ->
             // Select IDENT token. If failed, select OPERATOR token.
             tokensUnderCursor
             |> List.tryFind (fun { DraftToken.Kind = k } ->
@@ -189,6 +188,7 @@ module Lexer =
                   LeftColumn = token.Token.LeftColumn
                   RightColumn = token.RightColumn + 1
                   Text = lineStr.Substring(token.Token.LeftColumn, token.Token.FullMatchedLength) })
+        | SymbolLookupKind.ForCompletion
         | SymbolLookupKind.Simple ->
             tokensUnderCursor
             |> List.tryLast

src/FsAutoComplete.Core/ParseAndCheckResults.fs

@@ -576,7 +576,7 @@ type ParseAndCheckResults
               && entity.FullName.Contains "."
               && not (PrettyNaming.IsOperatorDisplayName entity.Symbol.DisplayName))
 
-          let token = Lexer.getSymbol pos.Line (pos.Column - 1) lineStr SymbolLookupKind.Simple [||]
+          let token = Lexer.getSymbol pos.Line (pos.Column - 1) lineStr SymbolLookupKind.ForCompletion [||]
 
           logger.info (
             Log.setMessage "TryGetCompletions - token: {token}"

test/FsAutoComplete.Tests.Lsp/CompletionTests.fs

@@ -34,7 +34,7 @@ let tests state =
 
           let completionParams: CompletionParams =
             { TextDocument = { Uri = Path.FilePathToUri path }
-              Position = { Line = 3; Character = 10 } // the '.' in 'Async.'
+              Position = { Line = 3; Character = 9 } // the '.' in 'Async.'
               Context =
                 Some
                   { triggerKind = CompletionTriggerKind.TriggerCharacter
@@ -146,7 +146,47 @@ let tests state =
               "completion should contain the list type"
           | Ok None -> failtest "Should have gotten some completion items"
           | Error e -> failtestf "Got an error while retrieving completions: %A" e
-        }) ]
+        })
+
+      testCaseAsync "completion before first character of expression" (async {
+        let! server, path = server
+        let completionParams : CompletionParams =
+          {
+            TextDocument = { Uri = Path.FilePathToUri path }
+            Position = { Line = 8; Character = 12 } // after the 'L' in 'List.'
+            Context = Some { triggerKind = CompletionTriggerKind.Invoked; triggerCharacter = None }
+          }
+        let! response = server.TextDocumentCompletion completionParams
+        match response with
+        | Ok (Some completions) ->
+          Expect.isGreaterThan completions.Items.Length 100 "should have a very long list of all symbols"
+          let firstItem = completions.Items.[0]
+          Expect.equal firstItem.Label "async" "first member should be async, alphabetically first in the full symbol list"
+        | Ok None ->
+          failtest "Should have gotten some completion items"
+        | Error e ->
+          failtestf "Got an error while retrieving completions: %A" e
+      })
+
+      testCaseAsync "completion after first character of expression" (async {
+        let! server, path = server
+        let completionParams : CompletionParams =
+          {
+            TextDocument = { Uri = Path.FilePathToUri path }
+            Position = { Line = 8; Character = 11 } // before the 'L' in 'List.'
+            Context = Some { triggerKind = CompletionTriggerKind.Invoked; triggerCharacter = None }
+          }
+        let! response = server.TextDocumentCompletion completionParams
+        match response with
+        | Ok (Some completions) ->
+          Expect.isGreaterThan completions.Items.Length 100 "should have a very long list of all symbols"
+          let firstItem = completions.Items.[0]
+          Expect.equal firstItem.Label "async" "first member should be async, alphabetically first in the full symbol list"
+        | Ok None ->
+          failtest "Should have gotten some completion items"
+        | Error e ->
+          failtestf "Got an error while retrieving completions: %A" e
+      }) ]
 
 ///Tests for getting autocomplete
 let autocompleteTest state =