feat(ts-client): isError helper function

src/Schema/core/Index.ts

@@ -9,4 +9,7 @@ export interface Index {
   objects: Record<string, Output.Object$2>
   unions: Record<string, Output.Union>
   interfaces: Record<string, Output.Interface>
+  error: {
+    objects: Record<string, Output.Object$2>
+  }
 }

src/client/client.error.test-d.ts

@@ -0,0 +1,17 @@
+/* eslint-disable */
+import { expectTypeOf, test } from 'vitest'
+import { isError } from '../../tests/_/schema/generated/Error.js'
+import * as Schema from '../../tests/_/schema/schema.js'
+import { create } from './client.js'
+
+const client = create<Schema.Index>({ schema: Schema.schema, schemaIndex: Schema.$Index })
+
+test('isError utility function narrows for error objects', async () => {
+  const result = await client.query.result({ $: { case: 'Object1' }, __typename: true })
+
+  if (isError(result)) {
+    expectTypeOf(result).toEqualTypeOf<{ __typename: 'ErrorOne' } | { __typename: 'ErrorTwo' }>()
+  } else {
+    expectTypeOf(result).toEqualTypeOf<null | { __typename: 'Object1' }>()
+  }
+})

src/generator/__snapshots__/files.test.ts.snap

@@ -1,6 +1,24 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
 exports[`generates types from GraphQL SDL file 1`] = `
+"type Include<T, U> = Exclude<T, Exclude<T, U>>
+
+type ObjectWithTypeName = { __typename: string }
+
+const ErrorObjectsTypeNameSelectedEnum = {} as Record<string, ObjectWithTypeName>
+
+const ErrorObjectsTypeNameSelected = Object.values(ErrorObjectsTypeNameSelectedEnum)
+
+type ErrorObjectsTypeNameSelected = (typeof ErrorObjectsTypeNameSelected)[number]
+
+export const isError = <$Value>(value: $Value): value is Include<$Value, ErrorObjectsTypeNameSelected> => {
+  return typeof value === 'object' && value !== null && '__typename' in value
+    && ErrorObjectsTypeNameSelected.some(_ => _.__typename === value.__typename)
+}
+"
+`;
+
+exports[`generates types from GraphQL SDL file 2`] = `
 "import { ResultSet, SelectionSet } from '../../../../../src/entrypoints/alpha/schema.js'
 import { Index } from './Index.js'
 
@@ -86,7 +104,7 @@ export type Interface<$SelectionSet extends SelectionSet.Interface<Index['interf
 "
 `;
 
-exports[`generates types from GraphQL SDL file 2`] = `
+exports[`generates types from GraphQL SDL file 3`] = `
 "/* eslint-disable */
 
 import type * as Schema from './SchemaBuildtime.js'
@@ -119,11 +137,14 @@ export interface Index {
     DateInterface1: Schema.Interface.DateInterface1
     Interface: Schema.Interface.Interface
   }
+  error: {
+    objects: {}
+  }
 }
 "
 `;
 
-exports[`generates types from GraphQL SDL file 3`] = `
+exports[`generates types from GraphQL SDL file 4`] = `
 "import type * as $ from '../../../../../src/entrypoints/alpha/schema.js'
 import type * as $Scalar from './Scalar.ts'
 
@@ -419,7 +440,7 @@ export namespace Union {
 "
 `;
 
-exports[`generates types from GraphQL SDL file 4`] = `
+exports[`generates types from GraphQL SDL file 5`] = `
 "import type * as CustomScalar from '../../../../_/customScalarCodecs.js'
 
 declare global {
@@ -433,7 +454,7 @@ export * from '../../../../_/customScalarCodecs.js'
 "
 `;
 
-exports[`generates types from GraphQL SDL file 5`] = `
+exports[`generates types from GraphQL SDL file 6`] = `
 "/* eslint-disable */
 
 import * as $ from '../../../../../src/entrypoints/alpha/schema.js'
@@ -648,11 +669,35 @@ export const $Index = {
     DateInterface1,
     Interface,
   },
+  error: {
+    objects: {},
+  },
 }
 "
 `;
 
 exports[`schema2 1`] = `
+"type Include<T, U> = Exclude<T, Exclude<T, U>>
+
+type ObjectWithTypeName = { __typename: string }
+
+const ErrorObjectsTypeNameSelectedEnum = {
+  ErrorOne: { __typename: 'ErrorOne' },
+  ErrorTwo: { __typename: 'ErrorTwo' },
+} as const
+
+const ErrorObjectsTypeNameSelected = Object.values(ErrorObjectsTypeNameSelectedEnum)
+
+type ErrorObjectsTypeNameSelected = (typeof ErrorObjectsTypeNameSelected)[number]
+
+export const isError = <$Value>(value: $Value): value is Include<$Value, ErrorObjectsTypeNameSelected> => {
+  return typeof value === 'object' && value !== null && '__typename' in value
+    && ErrorObjectsTypeNameSelected.some(_ => _.__typename === value.__typename)
+}
+"
+`;
+
+exports[`schema2 2`] = `
 "import { ResultSet, SelectionSet } from '../../../../src/entrypoints/alpha/schema.js'
 import { Index } from './Index.js'
 
@@ -683,6 +728,12 @@ export type Bar<$SelectionSet extends SelectionSet.Object<Index['objects']['Bar'
 export type DateObject1<$SelectionSet extends SelectionSet.Object<Index['objects']['DateObject1'], Index>> =
   ResultSet.Object$<$SelectionSet, Index['objects']['DateObject1'], Index>
 
+export type ErrorOne<$SelectionSet extends SelectionSet.Object<Index['objects']['ErrorOne'], Index>> =
+  ResultSet.Object$<$SelectionSet, Index['objects']['ErrorOne'], Index>
+
+export type ErrorTwo<$SelectionSet extends SelectionSet.Object<Index['objects']['ErrorTwo'], Index>> =
+  ResultSet.Object$<$SelectionSet, Index['objects']['ErrorTwo'], Index>
+
 export type Foo<$SelectionSet extends SelectionSet.Object<Index['objects']['Foo'], Index>> = ResultSet.Object$<
   $SelectionSet,
   Index['objects']['Foo'],
@@ -709,15 +760,24 @@ export type Object2ImplementingInterface<
 export type FooBarUnion<$SelectionSet extends SelectionSet.Union<Index['unions']['FooBarUnion'], Index>> =
   ResultSet.Union<$SelectionSet, Index['unions']['FooBarUnion'], Index>
 
+export type Result<$SelectionSet extends SelectionSet.Union<Index['unions']['Result'], Index>> = ResultSet.Union<
+  $SelectionSet,
+  Index['unions']['Result'],
+  Index
+>
+
 // Interface Types
 // ---------------
 
+export type Error<$SelectionSet extends SelectionSet.Interface<Index['interfaces']['Error'], Index>> =
+  ResultSet.Interface<$SelectionSet, Index['interfaces']['Error'], Index>
+
 export type Interface<$SelectionSet extends SelectionSet.Interface<Index['interfaces']['Interface'], Index>> =
   ResultSet.Interface<$SelectionSet, Index['interfaces']['Interface'], Index>
 "
 `;
 
-exports[`schema2 2`] = `
+exports[`schema2 3`] = `
 "/* eslint-disable */
 
 import type * as Schema from './SchemaBuildtime.js'
@@ -731,22 +791,32 @@ export interface Index {
   objects: {
     Bar: Schema.Object.Bar
     DateObject1: Schema.Object.DateObject1
+    ErrorOne: Schema.Object.ErrorOne
+    ErrorTwo: Schema.Object.ErrorTwo
     Foo: Schema.Object.Foo
     Object1: Schema.Object.Object1
     Object1ImplementingInterface: Schema.Object.Object1ImplementingInterface
     Object2ImplementingInterface: Schema.Object.Object2ImplementingInterface
   }
   unions: {
     FooBarUnion: Schema.Union.FooBarUnion
+    Result: Schema.Union.Result
   }
   interfaces: {
+    Error: Schema.Interface.Error
     Interface: Schema.Interface.Interface
   }
+  error: {
+    objects: {
+      ErrorOne: Schema.Object.ErrorOne
+      ErrorTwo: Schema.Object.ErrorTwo
+    }
+  }
 }
 "
 `;
 
-exports[`schema2 3`] = `
+exports[`schema2 4`] = `
 "import type * as $ from '../../../../src/entrypoints/alpha/schema.js'
 import type * as $Scalar from './Scalar.ts'
 
@@ -789,6 +859,12 @@ export namespace Root {
         string: $.Input.Nullable<$Scalar.String>
       }>
     >
+    result: $.Field<
+      $.Output.Nullable<Union.Result>,
+      $.Args<{
+        case: Enum.Case
+      }>
+    >
     unionFooBar: $.Field<$.Output.Nullable<Union.FooBarUnion>, null>
   }>
 }
@@ -798,7 +874,7 @@ export namespace Root {
 // ------------------------------------------------------------ //
 
 export namespace Enum {
-  // -- no types --
+  export type Case = $.Enum<'Case', ['ErrorOne', 'ErrorTwo', 'Object1']>
 }
 
 // ------------------------------------------------------------ //
@@ -814,6 +890,10 @@ export namespace InputObject {
 // ------------------------------------------------------------ //
 
 export namespace Interface {
+  export type Error = $.Interface<'Error', {
+    message: $.Field<$Scalar.String, null>
+  }, [Object.ErrorOne, Object.ErrorTwo]>
+
   export type Interface = $.Interface<'Interface', {
     id: $.Field<$.Output.Nullable<$Scalar.ID>, null>
   }, [Object.Object1ImplementingInterface, Object.Object2ImplementingInterface]>
@@ -832,6 +912,16 @@ export namespace Object {
     date1: $.Field<$.Output.Nullable<$Scalar.Date>, null>
   }>
 
+  export type ErrorOne = $.Object$2<'ErrorOne', {
+    infoId: $.Field<$.Output.Nullable<$Scalar.ID>, null>
+    message: $.Field<$Scalar.String, null>
+  }>
+
+  export type ErrorTwo = $.Object$2<'ErrorTwo', {
+    infoInt: $.Field<$.Output.Nullable<$Scalar.Int>, null>
+    message: $.Field<$Scalar.String, null>
+  }>
+
   /**
    * Object documentation.
    */
@@ -872,11 +962,13 @@ export namespace Union {
    * Union documentation.
    */
   export type FooBarUnion = $.Union<'FooBarUnion', [Object.Bar, Object.Foo]>
+
+  export type Result = $.Union<'Result', [Object.ErrorOne, Object.ErrorTwo, Object.Object1]>
 }
 "
 `;
 
-exports[`schema2 4`] = `
+exports[`schema2 5`] = `
 "import type * as CustomScalar from '../../customScalarCodecs.js'
 
 declare global {
@@ -890,12 +982,14 @@ export * from '../../customScalarCodecs.js'
 "
 `;
 
-exports[`schema2 5`] = `
+exports[`schema2 6`] = `
 "/* eslint-disable */
 
 import * as $ from '../../../../src/entrypoints/alpha/schema.js'
 import * as $Scalar from './Scalar.js'
 
+export const Case = $.Enum(\`Case\`, [\`ErrorOne\`, \`ErrorTwo\`, \`Object1\`])
+
 // @ts-ignore - circular types cannot infer. Ignore in case there are any. This comment is always added, it does not indicate if this particular type could infer or not.
 export const Bar = $.Object$(\`Bar\`, {
   int: $.field($.Output.Nullable($Scalar.Int)),
@@ -906,6 +1000,18 @@ export const DateObject1 = $.Object$(\`DateObject1\`, {
   date1: $.field($.Output.Nullable($Scalar.Date)),
 })
 
+// @ts-ignore - circular types cannot infer. Ignore in case there are any. This comment is always added, it does not indicate if this particular type could infer or not.
+export const ErrorOne = $.Object$(\`ErrorOne\`, {
+  infoId: $.field($.Output.Nullable($Scalar.ID)),
+  message: $.field($Scalar.String),
+})
+
+// @ts-ignore - circular types cannot infer. Ignore in case there are any. This comment is always added, it does not indicate if this particular type could infer or not.
+export const ErrorTwo = $.Object$(\`ErrorTwo\`, {
+  infoInt: $.field($.Output.Nullable($Scalar.Int)),
+  message: $.field($Scalar.String),
+})
+
 // @ts-ignore - circular types cannot infer. Ignore in case there are any. This comment is always added, it does not indicate if this particular type could infer or not.
 export const Foo = $.Object$(\`Foo\`, {
   id: $.field($.Output.Nullable($Scalar.ID)),
@@ -935,6 +1041,10 @@ export const Object2ImplementingInterface = $.Object$(\`Object2ImplementingInter
 // @ts-ignore - circular types cannot infer. Ignore in case there are any. This comment is always added, it does not indicate if this particular type could infer or not.
 export const FooBarUnion = $.Union(\`FooBarUnion\`, [Bar, Foo])
 
+// @ts-ignore - circular types cannot infer. Ignore in case there are any. This comment is always added, it does not indicate if this particular type could infer or not.
+export const Result = $.Union(\`Result\`, [ErrorOne, ErrorTwo, Object1])
+
+export const Error = $.Interface(\`Error\`, { message: $.field($Scalar.String) }, [ErrorOne, ErrorTwo])
 export const Interface = $.Interface(\`Interface\`, { id: $.field($.Output.Nullable($Scalar.ID)) }, [
   Object1ImplementingInterface,
   Object2ImplementingInterface,
@@ -966,6 +1076,7 @@ export const Query = $.Object$(\`Query\`, {
       string: $.Input.Nullable($Scalar.String),
     }),
   ),
+  result: $.field($.Output.Nullable(() => Result), $.Args({ case: Case })),
   unionFooBar: $.field($.Output.Nullable(() => FooBarUnion)),
 })
 
@@ -978,17 +1089,27 @@ export const $Index = {
   objects: {
     Bar,
     DateObject1,
+    ErrorOne,
+    ErrorTwo,
     Foo,
     Object1,
     Object1ImplementingInterface,
     Object2ImplementingInterface,
   },
   unions: {
     FooBarUnion,
+    Result,
   },
   interfaces: {
+    Error,
     Interface,
   },
+  error: {
+    objects: {
+      ErrorOne,
+      ErrorTwo,
+    },
+  },
 }
 "
 `;

src/generator/code/Error.ts

@@ -0,0 +1,34 @@
+import type { Config } from './generateCode.js'
+
+export const moduleNameError = `Error`
+
+export const generateError = (config: Config) => {
+  const code: string[] = []
+
+  code.push(
+    `type Include<T, U> = Exclude<T, Exclude<T, U>>`,
+    `type ObjectWithTypeName = { __typename: string }`,
+  )
+
+  code.push(`
+    const ErrorObjectsTypeNameSelectedEnum = {
+      ${config.error.objects.map(_ => `${_.name}: { __typename: '${_.name}' }`).join(`,\n`)}
+    } as ${config.error.objects.length > 0 ? `const` : `Record<string,ObjectWithTypeName>`}
+
+    const ErrorObjectsTypeNameSelected = Object.values(ErrorObjectsTypeNameSelectedEnum)
+
+    type ErrorObjectsTypeNameSelected = (typeof ErrorObjectsTypeNameSelected)[number]
+  `)
+
+  code.push(
+    `export const isError = <$Value>(value:$Value): value is Include<$Value, ErrorObjectsTypeNameSelected> =>  {
+      return typeof value === 'object' && value !== null && '__typename' in value &&
+      ErrorObjectsTypeNameSelected.some(_ => _.__typename === value.__typename)
+    }`,
+  )
+
+  return {
+    code: code.join(`\n\n`),
+    moduleName: moduleNameError,
+  }
+}

src/generator/code/Index.ts

@@ -30,6 +30,13 @@ export const generateIndex = (config: Config) => {
         interfaces: Code.objectFromEntries(
           config.typeMapByKind.GraphQLInterfaceType.map(_ => [_.name, `${namespace}.Interface.${_.name}`]),
         ),
+        // todo jsdoc comment saying:
+        // Objects that match this pattern name: /.../
+        error: Code.objectFrom({
+          objects: Code.objectFromEntries(
+            config.error.objects.map(_ => [_.name, `${namespace}.Object.${_.name}`]),
+          ),
+        }),
       }),
     ),
   ))