Fix accept suggestions, simplify suffix recovery

Author: intitni

Tool/Sources/SuggestionInjector/SuggestionInjector.swift

@@ -34,7 +34,7 @@ public struct SuggestionInjector {
         }
 
         let firstRemovedLine = content[safe: start.line]
-        let lastRemovedLine = content[safe: end.line]
+        let lastRemovedLine = completion.replacingLines[safe: max(0, end.line - start.line)]
         let startLine = max(0, start.line)
         let endLine = max(start.line, min(end.line, content.endIndex - 1))
         if startLine < content.endIndex {
@@ -72,7 +72,7 @@ public struct SuggestionInjector {
         let recoveredSuffixLength = recoverSuffixIfNeeded(
             endOfReplacedContent: end,
             toBeInserted: &toBeInserted,
-            lastRemovedLine: lastRemovedLine,
+            originalLastRemovedLine: lastRemovedLine,
             lineEnding: lineEnding
         )
 
@@ -90,52 +90,26 @@ public struct SuggestionInjector {
     func recoverSuffixIfNeeded(
         endOfReplacedContent end: CursorPosition,
         toBeInserted: inout [String],
-        lastRemovedLine: String?,
+        originalLastRemovedLine: String?,
         lineEnding: String
     ) -> Int {
         // If there is no line removed, there is no need to recover anything.
-        guard let lastRemovedLine, !lastRemovedLine.isEmptyOrNewLine else { return 0 }
+        guard let lastRemovedLine = originalLastRemovedLine,
+              !lastRemovedLine.isEmptyOrNewLine else { return 0 }
 
         let lastRemovedLineCleaned = lastRemovedLine.droppedLineBreak()
 
-        // If the replaced range covers the whole line, return immediately.
-        guard end.character >= 0, end.character - 1 < lastRemovedLineCleaned.utf16.count
-        else { return 0 }
-
-        // if we are not inserting anything, return immediately.
-        guard !toBeInserted.isEmpty,
-              let first = toBeInserted.first?.droppedLineBreak(), !first.isEmpty,
-              let last = toBeInserted.last?.droppedLineBreak(), !last.isEmpty
-        else { return 0 }
-
-        // case 1: user keeps typing as the suggestion suggests.
-
-        if first.hasPrefix(lastRemovedLineCleaned) {
-            return 0
-        }
-
-        // case 2: user also typed the suffix of the suggestion (or auto-completed by Xcode)
-
         // locate the split index, the prefix of which matches the suggestion prefix.
-        var splitIndex: String.Index?
-
-        for offset in end.character..<lastRemovedLineCleaned.utf16.count {
-            let proposedIndex = lastRemovedLineCleaned.utf16.index(
-                lastRemovedLineCleaned.utf16.startIndex,
-                offsetBy: offset,
-                limitedBy: lastRemovedLineCleaned.utf16.endIndex
-            ) ?? lastRemovedLineCleaned.utf16.endIndex
-            let prefix = String(lastRemovedLineCleaned[..<proposedIndex])
-            if first.hasPrefix(prefix) {
-                splitIndex = proposedIndex
-            }
-        }
+        let splitIndex = lastRemovedLineCleaned.utf16.index(
+            lastRemovedLineCleaned.utf16.startIndex,
+            offsetBy: end.character,
+            limitedBy: lastRemovedLineCleaned.utf16.endIndex
+        )
 
         // then check how many characters are not in the suffix of the suggestion.
-        guard let splitIndex else { return 0 }
+        guard let splitIndex, splitIndex != lastRemovedLineCleaned.utf16.endIndex else { return 0 }
 
         var suffix = String(lastRemovedLineCleaned[splitIndex...])
-        if last.hasSuffix(suffix) { return 0 }
 
         // remove the first adjacent placeholder in suffix which looks like `<#Hello#>`