add support for extract as interface

src/compiler/diagnosticMessages.json

@@ -5120,6 +5120,10 @@
         "category": "Message",
         "code": 95089
     },
+    "Extract to interface": {
+        "category": "Message",
+        "code": 95090
+    },
 
     "No value exists in scope for the shorthand property '{0}'. Either declare one or provide an initializer.": {
         "category": "Error",

src/services/refactors/extractType.ts

@@ -2,6 +2,7 @@
 namespace ts.refactor {
     const refactorName = "Extract type";
     const extractToTypeAlias = "Extract to type alias";
+    const extractToInterface = "Extract to interface";
     const extractToTypeDef = "Extract to typedef";
     registerRefactor(refactorName, {
         getAvailableActions(context): ReadonlyArray<ApplicableRefactorInfo> {
@@ -11,31 +12,51 @@ namespace ts.refactor {
             return [{
                 name: refactorName,
                 description: getLocaleSpecificMessage(Diagnostics.Extract_type),
-                actions: [info.isJS ? {
+                actions: info.isJS ? [{
                     name: extractToTypeDef, description: getLocaleSpecificMessage(Diagnostics.Extract_to_typedef)
-                } : {
-                        name: extractToTypeAlias, description: getLocaleSpecificMessage(Diagnostics.Extract_to_type_alias)
-                    }]
+                }] : append([{
+                    name: extractToTypeAlias, description: getLocaleSpecificMessage(Diagnostics.Extract_to_type_alias)
+                }], info.typeElements && {
+                    name: extractToInterface, description: getLocaleSpecificMessage(Diagnostics.Extract_to_interface)
+                })
             }];
         },
         getEditsForAction(context, actionName): RefactorEditInfo {
-            Debug.assert(actionName === extractToTypeAlias || actionName === extractToTypeDef, "Unexpected action name");
             const { file } = context;
             const info = Debug.assertDefined(getRangeToExtract(context), "Expected to find a range to extract");
-            Debug.assert(actionName === extractToTypeAlias && !info.isJS || actionName === extractToTypeDef && info.isJS, "Invalid actionName/JS combo");
 
             const name = getUniqueName("NewType", file);
-            const edits = textChanges.ChangeTracker.with(context, changes => info.isJS ?
-                doTypedefChange(changes, file, name, info.firstStatement, info.selection, info.typeParameters) :
-                doTypeAliasChange(changes, file, name, info.firstStatement, info.selection, info.typeParameters));
+            const edits = textChanges.ChangeTracker.with(context, changes => {
+                switch (actionName) {
+                    case extractToTypeAlias:
+                        Debug.assert(!info.isJS, "Invalid actionName/JS combo");
+                        return doTypeAliasChange(changes, file, name, info);
+                    case extractToTypeDef:
+                        Debug.assert(info.isJS, "Invalid actionName/JS combo");
+                        return doTypedefChange(changes, file, name, info);
+                    case extractToInterface:
+                        Debug.assert(!info.isJS && !!info.typeElements, "Invalid actionName/JS combo");
+                        return doInterfaceChange(changes, file, name, info as InterfaceInfo);
+                    default:
+                        Debug.fail("Unexpected action name");
+                }
+            });
 
             const renameFilename = file.fileName;
             const renameLocation = getRenameLocation(edits, renameFilename, name, /*preferLastLocation*/ false);
             return { edits, renameFilename, renameLocation };
         }
     });
 
-    interface Info { isJS: boolean; selection: TypeNode; firstStatement: Statement; typeParameters: ReadonlyArray<TypeParameterDeclaration>; }
+    interface TypeAliasInfo {
+        isJS: boolean; selection: TypeNode; firstStatement: Statement; typeParameters: ReadonlyArray<TypeParameterDeclaration>; typeElements?: ReadonlyArray<TypeElement>;
+    }
+
+    interface InterfaceInfo {
+        isJS: boolean; selection: TypeNode; firstStatement: Statement; typeParameters: ReadonlyArray<TypeParameterDeclaration>; typeElements: ReadonlyArray<TypeElement>;
+    }
+
+    type Info = TypeAliasInfo | InterfaceInfo;
 
     function getRangeToExtract(context: RefactorContext): Info | undefined {
         const { file, startPosition } = context;
@@ -51,7 +72,32 @@ namespace ts.refactor {
         const typeParameters = collectTypeParameters(checker, selection, firstStatement, file);
         if (!typeParameters) return undefined;
 
-        return { isJS, selection, firstStatement, typeParameters };
+        const typeElements = flattenTypeLiteralNodeReference(checker, selection);
+        return { isJS, selection, firstStatement, typeParameters, typeElements };
+    }
+
+    function flattenTypeLiteralNodeReference(checker: TypeChecker, node: TypeNode | undefined): ReadonlyArray<TypeElement> | undefined {
+        if (!node) return undefined;
+        if (isIntersectionTypeNode(node)) {
+            const result: TypeElement[] = [];
+            const seen = createMap<true>();
+            for (const type of node.types) {
+                const flattenedTypeMembers = flattenTypeLiteralNodeReference(checker, type);
+                if (!flattenedTypeMembers || !flattenedTypeMembers.every(type => type.name && addToSeen(seen, getNameFromPropertyName(type.name) as string))) {
+                    return undefined;
+                }
+
+                addRange(result, flattenedTypeMembers);
+            }
+            return result;
+        }
+        else if (isParenthesizedTypeNode(node)) {
+            return flattenTypeLiteralNodeReference(checker, node.type);
+        }
+        else if (isTypeLiteralNode(node)) {
+            return node.members;
+        }
+        return undefined;
     }
 
     function isStatementAndHasJSDoc(n: Node): n is (Statement & HasJSDoc) {
@@ -107,7 +153,9 @@ namespace ts.refactor {
         }
     }
 
-    function doTypeAliasChange(changes: textChanges.ChangeTracker, file: SourceFile, name: string, firstStatement: Statement, selection: TypeNode, typeParameters: ReadonlyArray<TypeParameterDeclaration>) {
+    function doTypeAliasChange(changes: textChanges.ChangeTracker, file: SourceFile, name: string, info: TypeAliasInfo) {
+        const { firstStatement, selection, typeParameters } = info;
+
         const newTypeNode = createTypeAliasDeclaration(
             /* decorators */ undefined,
             /* modifiers */ undefined,
@@ -119,7 +167,24 @@ namespace ts.refactor {
         changes.replaceNode(file, selection, createTypeReferenceNode(name, typeParameters.map(id => createTypeReferenceNode(id.name, /* typeArguments */ undefined))));
     }
 
-    function doTypedefChange(changes: textChanges.ChangeTracker, file: SourceFile, name: string, firstStatement: Statement, selection: TypeNode, typeParameters: ReadonlyArray<TypeParameterDeclaration>) {
+    function doInterfaceChange(changes: textChanges.ChangeTracker, file: SourceFile, name: string, info: InterfaceInfo) {
+        const { firstStatement, selection, typeParameters, typeElements } = info;
+
+        const newTypeNode = createInterfaceDeclaration(
+            /* decorators */ undefined,
+            /* modifiers */ undefined,
+            name,
+            typeParameters,
+            /* heritageClauses */ undefined,
+            typeElements
+        );
+        changes.insertNodeBefore(file, firstStatement, newTypeNode, /* blankLineBetween */ true);
+        changes.replaceNode(file, selection, createTypeReferenceNode(name, typeParameters.map(id => createTypeReferenceNode(id.name, /* typeArguments */ undefined))));
+    }
+
+    function doTypedefChange(changes: textChanges.ChangeTracker, file: SourceFile, name: string, info: Info) {
+        const { firstStatement, selection, typeParameters } = info;
+
         const node = <JSDocTypedefTag>createNode(SyntaxKind.JSDocTypedefTag);
         node.tagName = createIdentifier("typedef"); // TODO: jsdoc factory https://github.com/Microsoft/TypeScript/pull/29539
         node.fullName = createIdentifier(name);

tests/cases/fourslash/refactorExtractType60.ts

@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts' />
+
+//// function foo(a: /*a*/{ a: number | string, b: string }/*b*/) { }
+
+goTo.select("a", "b");
+edit.applyRefactor({
+    refactorName: "Extract type",
+    actionName: "Extract to interface",
+    actionDescription: "Extract to interface",
+    newContent: `interface /*RENAME*/NewType {
+    a: number | string;
+    b: string;
+}
+
+function foo(a: NewType) { }`,
+});

tests/cases/fourslash/refactorExtractType61.ts

@@ -0,0 +1,18 @@
+/// <reference path='fourslash.ts' />
+
+//// function foo(a: /*a*/{ a: number | string, b: string } & { c: string } & { d: boolean }/*b*/) { }
+
+goTo.select("a", "b");
+edit.applyRefactor({
+    refactorName: "Extract type",
+    actionName: "Extract to interface",
+    actionDescription: "Extract to interface",
+    newContent: `interface /*RENAME*/NewType {
+    a: number | string;
+    b: string;
+    c: string;
+    d: boolean;
+}
+
+function foo(a: NewType) { }`,
+});

tests/cases/fourslash/refactorExtractType62.ts

@@ -0,0 +1,7 @@
+/// <reference path='fourslash.ts' />
+
+//// type T = { c: string }
+//// function foo(a: /*a*/{ a: number | string, b: string } & T/*b*/) { }
+
+goTo.select("a", "b");
+verify.not.refactorAvailable("Extract type", "Extract to interface")

tests/cases/fourslash/refactorExtractType63.ts

@@ -0,0 +1,7 @@
+/// <reference path='fourslash.ts' />
+
+//// type T = { c: string } & { d: boolean }
+//// function foo(a: /*a*/{ a: number | string, b: string } & T/*b*/) { }
+
+goTo.select("a", "b");
+verify.not.refactorAvailable("Extract type", "Extract to interface")

tests/cases/fourslash/refactorExtractType64.ts

@@ -0,0 +1,7 @@
+/// <reference path='fourslash.ts' />
+
+//// type T = { c: string } & Record<string, string>
+//// function foo(a: /*a*/{ a: number | string, b: string } & T/*b*/) { }
+
+goTo.select("a", "b");
+verify.not.refactorAvailable("Extract type", "Extract to interface")

tests/cases/fourslash/refactorExtractType65.ts

@@ -0,0 +1,7 @@
+/// <reference path='fourslash.ts' />
+
+//// type T = { c: string }
+//// function foo(a: /*a*/T/*b*/) { }
+
+goTo.select("a", "b");
+verify.not.refactorAvailable("Extract type", "Extract to interface")

tests/cases/fourslash/refactorExtractType66.ts

@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts' />
+
+//// function foo<U>(a: /*a*/{ a: string } & { b: U }/*b*/) { }
+
+goTo.select("a", "b");
+edit.applyRefactor({
+    refactorName: "Extract type",
+    actionName: "Extract to interface",
+    actionDescription: "Extract to interface",
+    newContent: `interface /*RENAME*/NewType<U> {
+    a: string;
+    b: U;
+}
+
+function foo<U>(a: NewType<U>) { }`,
+});

tests/cases/fourslash/refactorExtractType67.ts

@@ -0,0 +1,6 @@
+/// <reference path='fourslash.ts' />
+
+//// function foo(a: /*a*/{ a: number | string, b: string } & { b: string } & { d: boolean }/*b*/) { }
+
+goTo.select("a", "b");
+verify.not.refactorAvailable("Extract type", "Extract to interface")

tests/cases/fourslash/refactorExtractType68.ts

@@ -0,0 +1,6 @@
+/// <reference path='fourslash.ts' />
+
+//// function foo(a: /*a*/{ a: number | string, b: string } & { b: number } & { d: boolean }/*b*/) { }
+
+goTo.select("a", "b");
+verify.not.refactorAvailable("Extract type", "Extract to interface")