Add optionalReplacementSpan to completions response (#40347)

* Add optionalReplacementRange to completions response

* Get the name right

* Fix unit tests

* Fix comment typo

* Fix comment typo

* Baseline

src/services/completions.ts

@@ -209,6 +209,11 @@ namespace ts.Completions {
         return { isGlobalCompletion: false, isMemberCompletion: false, isNewIdentifierLocation: false, entries };
     }
 
+    function getOptionalReplacementSpan(location: Node | undefined) {
+        // StringLiteralLike locations are handled separately in stringCompletions.ts
+        return location?.kind === SyntaxKind.Identifier ? createTextSpanFromNode(location) : undefined;
+    }
+
     function completionInfoFromData(sourceFile: SourceFile, typeChecker: TypeChecker, compilerOptions: CompilerOptions, log: Log, completionData: CompletionData, preferences: UserPreferences): CompletionInfo | undefined {
         const {
             symbols,
@@ -241,7 +246,7 @@ namespace ts.Completions {
                 kindModifiers: undefined,
                 sortText: SortText.LocationPriority,
             };
-            return { isGlobalCompletion: false, isMemberCompletion: true, isNewIdentifierLocation: false, entries: [entry] };
+            return { isGlobalCompletion: false, isMemberCompletion: true, isNewIdentifierLocation: false, optionalReplacementSpan: getOptionalReplacementSpan(location), entries: [entry] };
         }
 
         const entries: CompletionEntry[] = [];
@@ -305,7 +310,13 @@ namespace ts.Completions {
             entries.push(createCompletionEntryForLiteral(literal, preferences));
         }
 
-        return { isGlobalCompletion: isInSnippetScope, isMemberCompletion: isMemberCompletionKind(completionKind), isNewIdentifierLocation, entries };
+        return {
+            isGlobalCompletion: isInSnippetScope,
+            isMemberCompletion: isMemberCompletionKind(completionKind),
+            isNewIdentifierLocation,
+            optionalReplacementSpan: getOptionalReplacementSpan(location),
+            entries
+        };
     }
 
     function isUncheckedFile(sourceFile: SourceFile, compilerOptions: CompilerOptions): boolean {

src/services/stringCompletions.ts

@@ -12,10 +12,12 @@ namespace ts.Completions.StringCompletions {
         }
     }
 
-    function convertStringLiteralCompletions(completion: StringLiteralCompletion | undefined, contextToken: Node, sourceFile: SourceFile, checker: TypeChecker, log: Log, preferences: UserPreferences): CompletionInfo | undefined {
+    function convertStringLiteralCompletions(completion: StringLiteralCompletion | undefined, contextToken: StringLiteralLike, sourceFile: SourceFile, checker: TypeChecker, log: Log, preferences: UserPreferences): CompletionInfo | undefined {
         if (completion === undefined) {
             return undefined;
         }
+
+        const optionalReplacementSpan = createTextSpanFromStringLiteralLikeContent(contextToken);
         switch (completion.kind) {
             case StringLiteralCompletionKind.Paths:
                 return convertPathCompletions(completion.paths);
@@ -33,7 +35,7 @@ namespace ts.Completions.StringCompletions {
                     CompletionKind.String,
                     preferences
                 ); // Target will not be used, so arbitrary
-                return { isGlobalCompletion: false, isMemberCompletion: true, isNewIdentifierLocation: completion.hasIndexSignature, entries };
+                return { isGlobalCompletion: false, isMemberCompletion: true, isNewIdentifierLocation: completion.hasIndexSignature, optionalReplacementSpan, entries };
             }
             case StringLiteralCompletionKind.Types: {
                 const entries = completion.types.map(type => ({
@@ -43,7 +45,7 @@ namespace ts.Completions.StringCompletions {
                     sortText: "0",
                     replacementSpan: getReplacementSpanForContextToken(contextToken)
                 }));
-                return { isGlobalCompletion: false, isMemberCompletion: false, isNewIdentifierLocation: completion.isNewIdentifier, entries };
+                return { isGlobalCompletion: false, isMemberCompletion: false, isNewIdentifierLocation: completion.isNewIdentifier, optionalReplacementSpan, entries };
             }
             default:
                 return Debug.assertNever(completion);

src/services/types.ts

@@ -1087,6 +1087,12 @@ namespace ts {
         /** Not true for all global completions. This will be true if the enclosing scope matches a few syntax kinds. See `isSnippetScope`. */
         isGlobalCompletion: boolean;
         isMemberCompletion: boolean;
+        /**
+         * In the absence of `CompletionEntry["replacementSpan"], the editor may choose whether to use
+         * this span or its default one. If `CompletionEntry["replacementSpan"]` is defined, that span
+         * must be used to commit that completion entry.
+         */
+        optionalReplacementSpan?: TextSpan;
 
         /**
          * true when the current location also allows for a new identifier