Disable signature help on unresolved bare identifiers; add more declaration info on other unresolved calls

src/services/signatureHelp.ts

@@ -120,14 +120,22 @@ namespace ts.SignatureHelp {
         if (argumentInfo.invocation.kind === InvocationKind.Contextual) return undefined;
         // See if we can find some symbol with the call expression name that has call signatures.
         const expression = getExpressionFromInvocation(argumentInfo.invocation);
-        const name = isIdentifier(expression) ? expression.text : isPropertyAccessExpression(expression) ? expression.name.text : undefined;
+        const name = isPropertyAccessExpression(expression) ? expression.name.text : undefined;
         const typeChecker = program.getTypeChecker();
         return name === undefined ? undefined : firstDefined(program.getSourceFiles(), sourceFile =>
             firstDefined(sourceFile.getNamedDeclarations().get(name), declaration => {
                 const type = declaration.symbol && typeChecker.getTypeOfSymbolAtLocation(declaration.symbol, declaration);
                 const callSignatures = type && type.getCallSignatures();
                 if (callSignatures && callSignatures.length) {
-                    return typeChecker.runWithCancellationToken(cancellationToken, typeChecker => createSignatureHelpItems(callSignatures, callSignatures[0], argumentInfo, sourceFile, typeChecker));
+                    return typeChecker.runWithCancellationToken(
+                        cancellationToken,
+                        typeChecker => createSignatureHelpItems(
+                            callSignatures,
+                            callSignatures[0],
+                            argumentInfo,
+                            sourceFile,
+                            typeChecker,
+                            /*useFullPrefix*/ true));
                 }
             }));
     }
@@ -496,10 +504,11 @@ namespace ts.SignatureHelp {
         { isTypeParameterList, argumentCount, argumentsSpan: applicableSpan, invocation, argumentIndex }: ArgumentListInfo,
         sourceFile: SourceFile,
         typeChecker: TypeChecker,
+        useFullPrefix?: boolean,
     ): SignatureHelpItems {
         const enclosingDeclaration = getEnclosingDeclarationFromInvocation(invocation);
-        const callTargetSymbol = invocation.kind === InvocationKind.Contextual ? invocation.symbol : typeChecker.getSymbolAtLocation(getExpressionFromInvocation(invocation));
-        const callTargetDisplayParts = callTargetSymbol ? symbolToDisplayParts(typeChecker, callTargetSymbol, /*enclosingDeclaration*/ undefined, /*meaning*/ undefined) : emptyArray;
+        const callTargetSymbol = invocation.kind === InvocationKind.Contextual ? invocation.symbol : (typeChecker.getSymbolAtLocation(getExpressionFromInvocation(invocation)) || useFullPrefix && resolvedSignature.declaration?.symbol);
+        const callTargetDisplayParts = callTargetSymbol ? symbolToDisplayParts(typeChecker, callTargetSymbol, useFullPrefix ? sourceFile : undefined, /*meaning*/ undefined) : emptyArray;
         const items = map(candidates, candidateSignature => getSignatureHelpItem(candidateSignature, callTargetDisplayParts, isTypeParameterList, typeChecker, enclosingDeclaration, sourceFile));
 
         if (argumentIndex !== 0) {

tests/cases/fourslash/signatureHelpJSMissingIdentifier.ts

@@ -0,0 +1,9 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @checkJs: true
+
+// @Filename: test.js
+////log(/**/)
+
+verify.noSignatureHelp("");

tests/cases/fourslash/signatureHelpJSMissingPropertyAccess.ts

@@ -0,0 +1,19 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @checkJs: true
+
+// @Filename: test.js
+////foo.filter(/**/)
+
+goTo.marker("");
+verify.signatureHelp({
+  text: "ReadonlyArray.filter<S extends T>(predicate: (value: T, index: number, array: readonly T[]) => value is S, thisArg?: any): S[]",
+  overloadsCount: 2,
+  docComment: "Returns the elements of an array that meet the condition specified in a callback function.",
+  parameterDocComment: "A function that accepts up to three arguments. The filter method calls the predicate function one time for each element in the array.",
+  tags: [
+    { name: "param", text: "predicate A function that accepts up to three arguments. The filter method calls the predicate function one time for each element in the array." },
+    { name: "param", text: "thisArg An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value." }
+  ]
+});