Fixing delay caused in vscode due to pasteEdits

src/services/pasteEdits.ts

@@ -3,12 +3,17 @@ import {
     codefix,
     Debug,
     fileShouldUseJavaScriptRequire,
+    findAncestor,
     findIndex,
     forEachChild,
     formatting,
+    getNewLineOrDefaultFromHost,
     getQuotePreference,
+    getTokenAtPosition,
     isIdentifier,
     Program,
+    rangeContainsPosition,
+    rangeContainsRange,
     SourceFile,
     Statement,
     SymbolFlags,
@@ -56,17 +61,16 @@ function pasteEdits(
     cancellationToken: CancellationToken,
     changes: textChanges.ChangeTracker,
 ) {
-    let actualPastedText: string[] | undefined;
+    let actualPastedText: string | undefined;
     if (pastedText.length !== pasteLocations.length) {
-        actualPastedText = pastedText.length === 1 ? pastedText : [pastedText.join("\n")];
+        actualPastedText = pastedText.length === 1 ? pastedText[0] : pastedText.join(getNewLineOrDefaultFromHost(formatContext.host, formatContext.options));
     }
 
     const statements: Statement[] = [];
-
     let newText = targetFile.text;
     for (let i = pasteLocations.length - 1; i >= 0; i--) {
         const { pos, end } = pasteLocations[i];
-        newText = actualPastedText ? newText.slice(0, pos) + actualPastedText[0] + newText.slice(end) : newText.slice(0, pos) + pastedText[i] + newText.slice(end);
+        newText = actualPastedText ? newText.slice(0, pos) + actualPastedText + newText.slice(end) : newText.slice(0, pos) + pastedText[i] + newText.slice(end);
     }
 
     let importAdder: codefix.ImportAdder;
@@ -104,12 +108,46 @@ function pasteEdits(
                 preferences,
                 formatContext,
             };
-            forEachChild(updatedFile, function cb(node) {
-                if (isIdentifier(node) && !originalProgram?.getTypeChecker().resolveName(node.text, node, SymbolFlags.All, /*excludeGlobals*/ false)) {
-                    // generate imports
-                    importAdder.addImportForUnresolvedIdentifier(context, node, /*useAutoImportProvider*/ true);
-                }
-                node.forEachChild(cb);
+
+            // `updatedRanges` represent the new ranges that account for the offset changes caused by pasting new text and
+            // `offset` represents by how much the starting position of `pasteLocations` needs to be changed.
+            //
+            // We iterate over each updated range to get the node that wholly encloses the updated range.
+            // For each child of that node, we checked for unresolved identifiers
+            // within the updated range and try importing it.
+            let offset = 0;
+            pasteLocations.forEach((location, i) => {
+                const oldTextLength = location.end - location.pos;
+                const textToBePasted = actualPastedText ?? pastedText[i];
+                const startPos = location.pos + offset;
+                const endPos = startPos + textToBePasted.length;
+                const range: TextRange = { pos: startPos, end: endPos };
+                offset += textToBePasted.length - oldTextLength;
+
+                const enclosingNode = findAncestor(
+                    getTokenAtPosition(context.sourceFile, range.pos),
+                    ancestorNode => rangeContainsRange(ancestorNode, range),
+                );
+                if (!enclosingNode) return;
+
+                forEachChild(enclosingNode, function importUnresolvedIdentifiers(node) {
+                    const isImportCandidate = isIdentifier(node) &&
+                        rangeContainsPosition(range, node.getStart(updatedFile)) &&
+                        !updatedProgram?.getTypeChecker().resolveName(
+                            node.text,
+                            node,
+                            SymbolFlags.All,
+                            /*excludeGlobals*/ false,
+                        );
+                    if (isImportCandidate) {
+                        return importAdder.addImportForUnresolvedIdentifier(
+                            context,
+                            node,
+                            /*useAutoImportProvider*/ true,
+                        );
+                    }
+                    node.forEachChild(importUnresolvedIdentifiers);
+                });
             });
         }
         importAdder.writeFixes(changes, getQuotePreference(copiedFrom ? copiedFrom.file : targetFile, preferences));
@@ -125,8 +163,7 @@ function pasteEdits(
         changes.replaceRangeWithText(
             targetFile,
             { pos: paste.pos, end: paste.end },
-            actualPastedText ?
-                actualPastedText[0] : pastedText[i],
+            actualPastedText ?? pastedText[i],
         );
     });
 }