Support arrow function fields

Fixes #148

CHANGELOG.md

@@ -5,7 +5,7 @@
 Changes in this section are not yet released. If you need access to these changes before we cut a release, check out our `@main` NPM releases. Each commit on the main branch is [published to NPM](https://www.npmjs.com/package/grats?activeTab=versions) under the `main` tag.
 
 - **Features**
-  - ...
+  - Functional fields can now be defined using exported arrow functions.
 - **Bug Fixes**
   - ...
 

src/Errors.ts

@@ -561,3 +561,19 @@ export function userDefinedInfoTag(): string {
 export function invalidResolverParamType(): string {
   return "Unexpected GraphQL type used as resolver parameter. Resolver input arguments must be specified as a single `args` object literal: `args: {argName: ArgType}`.";
 }
+
+export function exportedArrowFunctionNotConst(): string {
+  return `Expected \`@${FIELD_TAG}\` arrow function to be declared as \`const\`.`;
+}
+
+export function exportedFieldVariableMultipleDeclarations(n: number): string {
+  return `Expected only one declaration when defining a \`@${FIELD_TAG}\`, found ${n}.`;
+}
+
+export function fieldVariableNotTopLevelExported(): string {
+  return `Expected \`@${FIELD_TAG}\` to be an exported top-level declaration. Grats needs to import resolver functions into it's generated schema module, so the resolver function must be exported from the module.`;
+}
+
+export function fieldVariableIsNotArrowFunction(): string {
+  return `Expected \`@${FIELD_TAG}\` on variable declaration to be attached to an arrow function.`;
+}

src/Extractor.ts

@@ -167,6 +167,8 @@ class Extractor {
         case FIELD_TAG:
           if (ts.isFunctionDeclaration(node)) {
             this.functionDeclarationExtendType(node, tag);
+          } else if (ts.isVariableStatement(node)) {
+            this.variableStatementExtendType(node, tag);
           } else if (isStaticMethod(node)) {
             this.staticMethodExtendType(node, tag);
           } else {
@@ -418,6 +420,71 @@ class Extractor {
     );
   }
 
+  variableStatementExtendType(node: ts.VariableStatement, tag: ts.JSDocTag) {
+    if (node.declarationList.declarations.length !== 1) {
+      return this.report(
+        node,
+        E.exportedFieldVariableMultipleDeclarations(
+          node.declarationList.declarations.length,
+        ),
+      );
+    }
+    const declaration = node.declarationList.declarations[0];
+
+    if (!(node.declarationList.flags & ts.NodeFlags.Const)) {
+      // Looks like there's no good way to find the location range of the `let`
+      // or `var` keyword.
+      return this.report(
+        node.declarationList,
+        E.exportedArrowFunctionNotConst(),
+      );
+    }
+
+    const funcName = this.expectNameIdentifier(declaration.name);
+    const name = this.entityName(declaration, tag);
+    if (name == null) return null;
+
+    if (!ts.isSourceFile(node.parent)) {
+      return this.report(node, E.fieldVariableNotTopLevelExported());
+    }
+
+    const tsModulePath = relativePath(node.getSourceFile().fileName);
+
+    const metadataDirective = this.gql.fieldMetadataDirective(node, {
+      tsModulePath,
+      name: null,
+      exportName: funcName == null ? null : funcName.text,
+    });
+
+    if (declaration.initializer == null) {
+      return this.report(node, E.fieldVariableIsNotArrowFunction());
+    }
+
+    if (!ts.isArrowFunction(declaration.initializer)) {
+      return this.report(node, E.fieldVariableIsNotArrowFunction());
+    }
+
+    const isExported = node.modifiers?.some((modifier) => {
+      return modifier.kind === ts.SyntaxKind.ExportKeyword;
+    });
+
+    if (!isExported) {
+      return this.report(
+        declaration.name,
+        E.fieldVariableNotTopLevelExported(),
+        [],
+        {
+          fixName: "add-export-keyword-to-arrow-function",
+          description:
+            "Add export keyword to exported arrow function with @gqlField",
+          changes: [Act.prefixNode(node, "export ")],
+        },
+      );
+    }
+
+    this.collectAbstractField(declaration.initializer, name, metadataDirective);
+  }
+
   functionDeclarationExtendType(
     node: ts.FunctionDeclaration,
     tag: ts.JSDocTag,
@@ -499,7 +566,7 @@ class Extractor {
   }
 
   collectAbstractField(
-    node: ts.FunctionDeclaration | ts.MethodDeclaration,
+    node: ts.FunctionDeclaration | ts.MethodDeclaration | ts.ArrowFunction,
     name: NameNode,
     metadataDirective: ConstDirectiveNode,
   ) {
@@ -1677,6 +1744,7 @@ class Extractor {
       | ts.EnumDeclaration
       | ts.TypeAliasDeclaration
       | ts.FunctionDeclaration
+      | ts.VariableDeclaration
       | ts.ParameterDeclaration,
     tag: ts.JSDocTag,
   ) {

src/tests/fixtures/extend_type/fieldAsArrowFunctionLet.invalid.ts

@@ -0,0 +1,9 @@
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export let greeting = (_: SomeType): string => {
+  return `Hello World`;
+};

src/tests/fixtures/extend_type/fieldAsArrowFunctionLet.invalid.ts.expected

@@ -0,0 +1,24 @@
+-----------------
+INPUT
+----------------- 
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export let greeting = (_: SomeType): string => {
+  return `Hello World`;
+};
+
+-----------------
+OUTPUT
+-----------------
+src/tests/fixtures/extend_type/fieldAsArrowFunctionLet.invalid.ts:7:8 - error: Expected `@gqlField` arrow function to be declared as `const`.
+
+7 export let greeting = (_: SomeType): string => {
+         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+8   return `Hello World`;
+  ~~~~~~~~~~~~~~~~~~~~~~~
+9 };
+  ~

src/tests/fixtures/extend_type/fieldAsArrowFunctionNotExported.invalid.ts

@@ -0,0 +1,9 @@
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+const greeting = (_: SomeType): string => {
+  return `Hello World`;
+};

src/tests/fixtures/extend_type/fieldAsArrowFunctionNotExported.invalid.ts.expected

@@ -0,0 +1,32 @@
+-----------------
+INPUT
+----------------- 
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+const greeting = (_: SomeType): string => {
+  return `Hello World`;
+};
+
+-----------------
+OUTPUT
+-----------------
+-- Error Report --
+src/tests/fixtures/extend_type/fieldAsArrowFunctionNotExported.invalid.ts:7:7 - error: Expected `@gqlField` to be an exported top-level declaration. Grats needs to import resolver functions into it's generated schema module, so the resolver function must be exported from the module.
+
+7 const greeting = (_: SomeType): string => {
+        ~~~~~~~~
+
+
+-- Code Action: "Add export keyword to exported arrow function with @gqlField" (add-export-keyword-to-arrow-function) --
+- Original
++ Fixed
+
+@@ -6,3 +6,3 @@
+  /** @gqlField */
+- const greeting = (_: SomeType): string => {
++ export const greeting = (_: SomeType): string => {
+    return `Hello World`;

src/tests/fixtures/extend_type/fieldAsArrowFunctionVar.invalid.ts

@@ -0,0 +1,9 @@
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+var greeting = (_: SomeType): string => {
+  return `Hello World`;
+};

src/tests/fixtures/extend_type/fieldAsArrowFunctionVar.invalid.ts.expected

@@ -0,0 +1,24 @@
+-----------------
+INPUT
+----------------- 
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+var greeting = (_: SomeType): string => {
+  return `Hello World`;
+};
+
+-----------------
+OUTPUT
+-----------------
+src/tests/fixtures/extend_type/fieldAsArrowFunctionVar.invalid.ts:7:1 - error: Expected `@gqlField` arrow function to be declared as `const`.
+
+7 var greeting = (_: SomeType): string => {
+  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+8   return `Hello World`;
+  ~~~~~~~~~~~~~~~~~~~~~~~
+9 };
+  ~

src/tests/fixtures/extend_type/fieldAsExportedArrowFunction.ts

@@ -0,0 +1,9 @@
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export const greeting = (_: SomeType): string => {
+  return `Hello World`;
+};

src/tests/fixtures/extend_type/fieldAsExportedArrowFunction.ts.expected

@@ -0,0 +1,42 @@
+-----------------
+INPUT
+----------------- 
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export const greeting = (_: SomeType): string => {
+  return `Hello World`;
+};
+
+-----------------
+OUTPUT
+-----------------
+-- SDL --
+type SomeType {
+  greeting: String @metadata(exportName: "greeting", tsModulePath: "grats/src/tests/fixtures/extend_type/fieldAsExportedArrowFunction.ts")
+}
+-- TypeScript --
+import { greeting as someTypeGreetingResolver } from "./fieldAsExportedArrowFunction";
+import { GraphQLSchema, GraphQLObjectType, GraphQLString } from "graphql";
+export function getSchema(): GraphQLSchema {
+    const SomeTypeType: GraphQLObjectType = new GraphQLObjectType({
+        name: "SomeType",
+        fields() {
+            return {
+                greeting: {
+                    name: "greeting",
+                    type: GraphQLString,
+                    resolve(source) {
+                        return someTypeGreetingResolver(source);
+                    }
+                }
+            };
+        }
+    });
+    return new GraphQLSchema({
+        types: [SomeTypeType]
+    });
+}

src/tests/fixtures/extend_type/fieldAsExportedAsyncArrowFunction.ts

@@ -0,0 +1,9 @@
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export const greeting = async (_: SomeType): Promise<string> => {
+  return `Hello World`;
+};

src/tests/fixtures/extend_type/fieldAsExportedAsyncArrowFunction.ts.expected

@@ -0,0 +1,42 @@
+-----------------
+INPUT
+----------------- 
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export const greeting = async (_: SomeType): Promise<string> => {
+  return `Hello World`;
+};
+
+-----------------
+OUTPUT
+-----------------
+-- SDL --
+type SomeType {
+  greeting: String @metadata(exportName: "greeting", tsModulePath: "grats/src/tests/fixtures/extend_type/fieldAsExportedAsyncArrowFunction.ts")
+}
+-- TypeScript --
+import { greeting as someTypeGreetingResolver } from "./fieldAsExportedAsyncArrowFunction";
+import { GraphQLSchema, GraphQLObjectType, GraphQLString } from "graphql";
+export function getSchema(): GraphQLSchema {
+    const SomeTypeType: GraphQLObjectType = new GraphQLObjectType({
+        name: "SomeType",
+        fields() {
+            return {
+                greeting: {
+                    name: "greeting",
+                    type: GraphQLString,
+                    resolve(source) {
+                        return someTypeGreetingResolver(source);
+                    }
+                }
+            };
+        }
+    });
+    return new GraphQLSchema({
+        types: [SomeTypeType]
+    });
+}

src/tests/fixtures/extend_type/fieldAsExportedMultipleVariables.invalid.ts

@@ -0,0 +1,12 @@
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export const greeting = (_: SomeType): string => {
+    return `Hello World`;
+  },
+  anotherGreeting = (_: SomeType): string => {
+    return `Hello World`;
+  };

src/tests/fixtures/extend_type/fieldAsExportedMultipleVariables.invalid.ts.expected

@@ -0,0 +1,30 @@
+-----------------
+INPUT
+----------------- 
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export const greeting = (_: SomeType): string => {
+    return `Hello World`;
+  },
+  anotherGreeting = (_: SomeType): string => {
+    return `Hello World`;
+  };
+
+-----------------
+OUTPUT
+-----------------
+src/tests/fixtures/extend_type/fieldAsExportedMultipleVariables.invalid.ts:7:1 - error: Expected only one declaration when defining a `@gqlField`, found 2.
+
+  7 export const greeting = (_: SomeType): string => {
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  8     return `Hello World`;
+    ~~~~~~~~~~~~~~~~~~~~~~~~~
+... 
+ 11     return `Hello World`;
+    ~~~~~~~~~~~~~~~~~~~~~~~~~
+ 12   };
+    ~~~~

src/tests/fixtures/extend_type/fieldAsExportedNothing.invalid.ts

@@ -0,0 +1,7 @@
+/** @gqlType */
+class SomeType {
+  // No fields
+}
+
+/** @gqlField */
+export const greeting;