Support a 'recommended' completion entry

Author: Andy Hanson

Diff for: src/compiler/checker.ts

@@ -254,6 +254,7 @@ namespace ts {
                 return resolveName(location, escapeLeadingUnderscores(name), meaning, /*nameNotFoundMessage*/ undefined, /*nameArg*/ undefined, /*isUse*/ false);
             },
             getJsxNamespace: () => unescapeLeadingUnderscores(getJsxNamespace()),
+            getAccessibleSymbolChain,
         };
 
         const tupleTypes: GenericType[] = [];
@@ -738,10 +739,6 @@ namespace ts {
             return nodeLinks[nodeId] || (nodeLinks[nodeId] = { flags: 0 });
         }
 
-        function getObjectFlags(type: Type): ObjectFlags {
-            return type.flags & TypeFlags.Object ? (<ObjectType>type).objectFlags : 0;
-        }
-
         function isGlobalSourceFile(node: Node) {
             return node.kind === SyntaxKind.SourceFile && !isExternalOrCommonJsModule(<SourceFile>node);
         }
@@ -10146,20 +10143,6 @@ namespace ts {
                 !hasBaseType(checkClass, getDeclaringClass(p)) : false) ? undefined : checkClass;
         }
 
-        // Return true if the given type is the constructor type for an abstract class
-        function isAbstractConstructorType(type: Type) {
-            if (getObjectFlags(type) & ObjectFlags.Anonymous) {
-                const symbol = type.symbol;
-                if (symbol && symbol.flags & SymbolFlags.Class) {
-                    const declaration = getClassLikeDeclarationOfSymbol(symbol);
-                    if (declaration && hasModifier(declaration, ModifierFlags.Abstract)) {
-                        return true;
-                    }
-                }
-            }
-            return false;
-        }
-
         // Return true if the given type is deeply nested. We consider this to be the case when structural type comparisons
         // for 5 or more occurrences or instantiations of the type have been recorded on the given stack. It is possible,
         // though highly unlikely, for this test to be true in a situation where a chain of instantiations is not infinitely
@@ -13409,7 +13392,7 @@ namespace ts {
         //   the contextual type of an initializer expression is the type annotation of the containing declaration, if present.
         function getContextualTypeForInitializerExpression(node: Expression): Type {
             const declaration = <VariableLikeDeclaration>node.parent;
-            if (node === declaration.initializer) {
+            if (node === declaration.initializer || node.kind === SyntaxKind.EqualsToken) {
                 const typeNode = getEffectiveTypeAnnotationNode(declaration);
                 if (typeNode) {
                     return getTypeFromTypeNode(typeNode);
@@ -13529,7 +13512,8 @@ namespace ts {
 
         function getContextualTypeForBinaryOperand(node: Expression): Type {
             const binaryExpression = <BinaryExpression>node.parent;
-            const operator = binaryExpression.operatorToken.kind;
+            const { operatorToken } = binaryExpression;
+            const operator = operatorToken.kind;
             if (isAssignmentOperator(operator)) {
                 if (node === binaryExpression.right) {
                     // Don't do this for special property assignments to avoid circularity
@@ -13567,10 +13551,26 @@ namespace ts {
                     return getContextualType(binaryExpression);
                 }
             }
+            else if (node === operatorToken && isEquationOperator(operator)) {
+                // For completions after `x === `
+                return getTypeOfExpression(binaryExpression.left);
+            }
 
             return undefined;
         }
 
+        function isEquationOperator(operator: SyntaxKind) {
+            switch (operator) {
+                case SyntaxKind.EqualsEqualsEqualsToken:
+                case SyntaxKind.EqualsEqualsToken:
+                case SyntaxKind.ExclamationEqualsEqualsToken:
+                case SyntaxKind.ExclamationEqualsToken:
+                    return true;
+                default:
+                    return false;
+            }
+        }
+
         function getTypeOfPropertyOfContextualType(type: Type, name: __String) {
             return mapType(type, t => {
                 const prop = t.flags & TypeFlags.StructuredType ? getPropertyOfType(t, name) : undefined;
@@ -13761,9 +13761,13 @@ namespace ts {
                     return getContextualTypeForReturnExpression(node);
                 case SyntaxKind.YieldExpression:
                     return getContextualTypeForYieldOperand(<YieldExpression>parent);
-                case SyntaxKind.CallExpression:
                 case SyntaxKind.NewExpression:
-                    return getContextualTypeForArgument(<CallExpression>parent, node);
+                    if (node.kind === SyntaxKind.NewKeyword) { // for completions after `new `
+                        return getContextualType(parent as NewExpression);
+                    }
+                    // falls through
+                case SyntaxKind.CallExpression:
+                    return getContextualTypeForArgument(<CallExpression | NewExpression>parent, node);
                 case SyntaxKind.TypeAssertionExpression:
                 case SyntaxKind.AsExpression:
                     return getTypeFromTypeNode((<AssertionExpression>parent).type);
@@ -13797,6 +13801,12 @@ namespace ts {
                 case SyntaxKind.JsxOpeningElement:
                 case SyntaxKind.JsxSelfClosingElement:
                     return getAttributesTypeFromJsxOpeningLikeElement(<JsxOpeningLikeElement>parent);
+                case SyntaxKind.CaseClause: {
+                    if (node.kind === SyntaxKind.CaseKeyword) { // for completions after `case `
+                        const switchStatement = (parent as CaseClause).parent.parent;
+                        return getTypeOfExpression(switchStatement.expression);
+                    }
+                }
             }
             return undefined;
         }
@@ -22117,10 +22127,6 @@ namespace ts {
             return getCheckFlags(s) & CheckFlags.Instantiated ? (<TransientSymbol>s).target : s;
         }
 
-        function getClassLikeDeclarationOfSymbol(symbol: Symbol): Declaration {
-            return forEach(symbol.declarations, d => isClassLike(d) ? d : undefined);
-        }
-
         function getClassOrInterfaceDeclarationsOfSymbol(symbol: Symbol) {
             return filter(symbol.declarations, (d: Declaration): d is ClassDeclaration | InterfaceDeclaration =>
                 d.kind === SyntaxKind.ClassDeclaration || d.kind === SyntaxKind.InterfaceDeclaration);

Diff for: src/compiler/types.ts

@@ -2781,6 +2781,17 @@ namespace ts {
         /* @internal */ getAllPossiblePropertiesOfTypes(type: ReadonlyArray<Type>): Symbol[];
         /* @internal */ resolveName(name: string, location: Node, meaning: SymbolFlags): Symbol | undefined;
         /* @internal */ getJsxNamespace(): string;
+
+        /**
+         * Note that this will return undefined in the following case:
+         *     // a.ts
+         *     export namespace N { export class C { } }
+         *     // b.ts
+         *     <<enclosingDeclaration>>
+         * Where `C` is the symbol we're looking for.
+         * This should be called in a loop climbing parents of the symbol, so we'll get `N`.
+         */
+        /* @internal */ getAccessibleSymbolChain(symbol: Symbol, enclosingDeclaration: Node | undefined, meaning: SymbolFlags, useOnlyExternalAliasing: boolean): Symbol[] | undefined;
     }
 
     export enum NodeBuilderFlags {

Diff for: src/compiler/utilities.ts

@@ -464,7 +464,6 @@ namespace ts {
         return isExternalModule(node) || compilerOptions.isolatedModules || ((getEmitModuleKind(compilerOptions) === ModuleKind.CommonJS) && !!node.commonJsModuleIndicator);
     }
 
-    /* @internal */
     export function isBlockScope(node: Node, parentNode: Node) {
         switch (node.kind) {
             case SyntaxKind.SourceFile:
@@ -492,7 +491,6 @@ namespace ts {
         return false;
     }
 
-    /* @internal */
     export function isDeclarationWithTypeParameters(node: Node): node is DeclarationWithTypeParameters;
     export function isDeclarationWithTypeParameters(node: DeclarationWithTypeParameters): node is DeclarationWithTypeParameters {
         switch (node.kind) {
@@ -522,7 +520,6 @@ namespace ts {
         }
     }
 
-    /* @internal */
     export function isAnyImportSyntax(node: Node): node is AnyImportSyntax {
         switch (node.kind) {
             case SyntaxKind.ImportDeclaration:
@@ -1742,7 +1739,6 @@ namespace ts {
         }
     }
 
-    /* @internal */
     // See GH#16030
     export function isAnyDeclarationName(name: Node): boolean {
         switch (name.kind) {
@@ -3039,7 +3035,6 @@ namespace ts {
         return flags;
     }
 
-    /* @internal */
     export function getModifierFlagsNoCache(node: Node): ModifierFlags {
 
         let flags = ModifierFlags.None;
@@ -3623,6 +3618,27 @@ namespace ts {
             directory = parentPath;
         }
     }
+
+    // Return true if the given type is the constructor type for an abstract class
+    export function isAbstractConstructorType(type: Type): boolean {
+        return !!(getObjectFlags(type) & ObjectFlags.Anonymous) && !!type.symbol && isAbstractConstructorSymbol(type.symbol);
+    }
+
+    export function isAbstractConstructorSymbol(symbol: Symbol): boolean {
+        if (symbol.flags & SymbolFlags.Class) {
+            const declaration = getClassLikeDeclarationOfSymbol(symbol);
+            return !!declaration && hasModifier(declaration, ModifierFlags.Abstract);
+        }
+        return false;
+    }
+
+    export function getClassLikeDeclarationOfSymbol(symbol: Symbol): Declaration | undefined {
+        return find(symbol.declarations, isClassLike);
+    }
+
+    export function getObjectFlags(type: Type): ObjectFlags {
+        return type.flags & TypeFlags.Object ? (<ObjectType>type).objectFlags : 0;
+    }
 }
 
 namespace ts {

Diff for: src/harness/fourslash.ts

@@ -888,7 +888,7 @@ namespace FourSlash {
          * @param expectedKind the kind of symbol (see ScriptElementKind)
          * @param spanIndex the index of the range that the completion item's replacement text span should match
          */
-        public verifyCompletionListDoesNotContain(entryId: ts.Completions.CompletionEntryIdentifier, expectedText?: string, expectedDocumentation?: string, expectedKind?: string, spanIndex?: number, options?: ts.GetCompletionsAtPositionOptions) {
+        public verifyCompletionListDoesNotContain(entryId: ts.Completions.CompletionEntryIdentifier, expectedText?: string, expectedDocumentation?: string, expectedKind?: string, spanIndex?: number, options?: FourSlashInterface.CompletionsAtOptions) {
             let replacementSpan: ts.TextSpan;
             if (spanIndex !== undefined) {
                 replacementSpan = this.getTextSpanForRangeAtIndex(spanIndex);
@@ -1207,7 +1207,7 @@ Actual: ${stringify(fullActual)}`);
             this.raiseError(`verifyReferencesAtPositionListContains failed - could not find the item: ${stringify(missingItem)} in the returned list: (${stringify(references)})`);
         }
 
-        private getCompletionListAtCaret(options?: ts.GetCompletionsAtPositionOptions): ts.CompletionInfo {
+        private getCompletionListAtCaret(options?: FourSlashInterface.CompletionsAtOptions): ts.CompletionInfo {
             return this.languageService.getCompletionsAtPosition(this.activeFile.fileName, this.currentCaretPosition, options);
         }
 
@@ -1721,7 +1721,7 @@ Actual: ${stringify(fullActual)}`);
             const longestNameLength = max(entries, m => m.name.length);
             const longestKindLength = max(entries, m => m.kind.length);
             entries.sort((m, n) => m.sortText > n.sortText ? 1 : m.sortText < n.sortText ? -1 : m.name > n.name ? 1 : m.name < n.name ? -1 : 0);
-            const membersString = entries.map(m => `${pad(m.name, longestNameLength)} ${pad(m.kind, longestKindLength)} ${m.kindModifiers} ${m.source === undefined ? "" : m.source}`).join("\n");
+            const membersString = entries.map(m => `${pad(m.name, longestNameLength)} ${pad(m.kind, longestKindLength)} ${m.kindModifiers} ${m.isRecommended ? "recommended " : ""}${m.source === undefined ? "" : m.source}`).join("\n");
             Harness.IO.log(membersString);
         }
 
@@ -3102,7 +3102,8 @@ Actual: ${stringify(fullActual)}`);
                         assert.isTrue(TestState.textSpansEqual(span, item.replacementSpan), this.assertionMessageAtLastKnownMarker(stringify(span) + " does not equal " + stringify(item.replacementSpan) + " replacement span for " + entryId));
                     }
 
-                    assert.equal(item.hasAction, hasAction);
+                    assert.equal(item.hasAction, hasAction, "hasAction");
+                    assert.equal(item.isRecommended, options && options.isRecommended, "isRecommended");
 
                     return;
                 }
@@ -4549,12 +4550,13 @@ namespace FourSlashInterface {
         newContent: string;
     }
 
-    export interface CompletionsAtOptions {
+    export interface CompletionsAtOptions extends ts.GetCompletionsAtPositionOptions {
         isNewIdentifierLocation?: boolean;
     }
 
     export interface VerifyCompletionListContainsOptions extends ts.GetCompletionsAtPositionOptions {
         sourceDisplay: string;
+        isRecommended?: true;
     }
 
     export interface NewContentOptions {

Diff for: src/server/client.ts

@@ -180,14 +180,15 @@ namespace ts.server {
                 isGlobalCompletion: false,
                 isMemberCompletion: false,
                 isNewIdentifierLocation: false,
-                entries: response.body.map(entry => {
-
+                entries: response.body.map<CompletionEntry>(entry => {
                     if (entry.replacementSpan !== undefined) {
-                        const { name, kind, kindModifiers, sortText, replacementSpan } = entry;
-                        return { name, kind, kindModifiers, sortText, replacementSpan: this.decodeSpan(replacementSpan, fileName) };
+                        const { name, kind, kindModifiers, sortText, replacementSpan, hasAction, source, isRecommended } = entry;
+                        // TODO: GH#241
+                        const res: CompletionEntry = { name, kind, kindModifiers, sortText, replacementSpan: this.decodeSpan(replacementSpan, fileName), hasAction, source, isRecommended };
+                        return res;
                     }
 
-                    return entry as { name: string, kind: ScriptElementKind, kindModifiers: string, sortText: string };
+                    return entry as { name: string, kind: ScriptElementKind, kindModifiers: string, sortText: string }; // TODO: GH#18217
                 })
             };
         }

Diff for: src/server/protocol.ts

@@ -1701,8 +1701,9 @@ namespace ts.server.protocol {
          */
         sortText: string;
         /**
-         * An optional span that indicates the text to be replaced by this completion item. If present,
-         * this span should be used instead of the default one.
+         * An optional span that indicates the text to be replaced by this completion item.
+         * If present, this span should be used instead of the default one.
+         * It will be set if the required span differs from the one generated by the default replacement behavior.
          */
         replacementSpan?: TextSpan;
         /**
@@ -1714,6 +1715,12 @@ namespace ts.server.protocol {
          * Identifier (not necessarily human-readable) identifying where this completion came from.
          */
         source?: string;
+        /**
+         * If true, this completion should be highlighted as recommended. There will only be one of these.
+         * This will be set when we know the user should write an expression with a certain type and that type is an enum or constructable class.
+         * Then either that enum/class or a namespace containing it will be the recommended symbol.
+         */
+        isRecommended?: true;
     }
 
     /**

Diff for: src/server/session.ts

@@ -1204,10 +1204,10 @@ namespace ts.server {
             if (simplifiedResult) {
                 return mapDefined<CompletionEntry, protocol.CompletionEntry>(completions && completions.entries, entry => {
                     if (completions.isMemberCompletion || startsWith(entry.name.toLowerCase(), prefix.toLowerCase())) {
-                        const { name, kind, kindModifiers, sortText, replacementSpan, hasAction, source } = entry;
+                        const { name, kind, kindModifiers, sortText, replacementSpan, hasAction, source, isRecommended } = entry;
                         const convertedSpan = replacementSpan ? this.toLocationTextSpan(replacementSpan, scriptInfo) : undefined;
                         // Use `hasAction || undefined` to avoid serializing `false`.
-                        return { name, kind, kindModifiers, sortText, replacementSpan: convertedSpan, hasAction: hasAction || undefined, source };
+                        return { name, kind, kindModifiers, sortText, replacementSpan: convertedSpan, hasAction: hasAction || undefined, source, isRecommended };
                     }
                 }).sort((a, b) => compareStringsCaseSensitiveUI(a.name, b.name));
             }