feat: handle disjoint unions cleanly (#24)

This gives a clear error message for disjoint unions, providing there is a single key that is a string, number of enum and has a unique, distinct value in all items within the union. If this is the case, instead of construcing an `anyOf` we use a series of `if`/`then`/`else` constructs to select the appropriate schema based on the value of that key, if the key doesn't match any schemas, we default to a schema that lists the valid values for that key.

package.json

@@ -21,7 +21,7 @@
     "prebuild": "yarn clean",
     "build": "tsc",
     "build:watch": "yarn build -w",
-    "postbuild": "node lib/usage && node lib/cli src/Example.ts ExampleType && rimraf lib/__tests__",
+    "postbuild": "node lib/usage && node lib/cli src/Example.ts ExampleType && node lib/cli src/DisjointUnionExample.ts --collection && rimraf lib/__tests__",
     "precommit": "pretty-quick --staged",
     "prepush": "yarn prettier:diff && yarn test",
     "prettier": "prettier --ignore-path .gitignore --write './**/*.{js,jsx,ts,tsx}'",

src/DisjointUnionExample.ts

@@ -0,0 +1,22 @@
+export enum EntityTypes {
+  TypeOne = 'TypeOne',
+  TypeTwo = 'TypeTwo',
+  TypeThree = 'TypeThree',
+}
+export interface EntityOne {
+  type: EntityTypes.TypeOne;
+  foo: string;
+}
+export interface EntityTwo {
+  type: EntityTypes.TypeTwo;
+  bar: string;
+}
+export type Entity =
+  | EntityOne
+  | EntityTwo
+  | {type: EntityTypes.TypeThree; baz: number};
+
+export type Value =
+  | {number: 0; foo: string}
+  | {number: 1; bar: string}
+  | {number: 2; baz: string};

src/DisjointUnionExample.validator.ts

@@ -0,0 +1,240 @@
+/* tslint:disable */
+// generated by typescript-json-validator
+import Ajv = require('ajv');
+import {
+  EntityTypes,
+  EntityOne,
+  EntityTwo,
+  Entity,
+  Value,
+} from './DisjointUnionExample';
+export const ajv = new Ajv({
+  allErrors: true,
+  coerceTypes: false,
+  format: 'fast',
+  nullable: true,
+  unicode: true,
+  uniqueItems: true,
+  useDefaults: true,
+});
+
+ajv.addMetaSchema(require('ajv/lib/refs/json-schema-draft-06.json'));
+
+export {EntityTypes, EntityOne, EntityTwo, Entity, Value};
+export const Schema = {
+  $schema: 'http://json-schema.org/draft-07/schema#',
+  definitions: {
+    Entity: {
+      else: {
+        else: {
+          else: {
+            properties: {
+              type: {
+                enum: ['TypeOne', 'TypeTwo', 'TypeThree'],
+                type: 'string',
+              },
+            },
+            required: ['type'],
+          },
+          if: {
+            properties: {
+              type: {
+                enum: ['TypeThree'],
+                type: 'string',
+              },
+            },
+            required: ['type'],
+          },
+          then: {
+            defaultProperties: [],
+            properties: {
+              baz: {
+                type: 'number',
+              },
+              type: {
+                enum: ['TypeThree'],
+                type: 'string',
+              },
+            },
+            required: ['baz', 'type'],
+            type: 'object',
+          },
+        },
+        if: {
+          properties: {
+            type: {
+              enum: ['TypeTwo'],
+              type: 'string',
+            },
+          },
+          required: ['type'],
+        },
+        then: {
+          $ref: '#/definitions/EntityTwo',
+        },
+      },
+      if: {
+        properties: {
+          type: {
+            enum: ['TypeOne'],
+            type: 'string',
+          },
+        },
+        required: ['type'],
+      },
+      then: {
+        $ref: '#/definitions/EntityOne',
+      },
+    },
+    EntityOne: {
+      defaultProperties: [],
+      properties: {
+        foo: {
+          type: 'string',
+        },
+        type: {
+          enum: ['TypeOne'],
+          type: 'string',
+        },
+      },
+      required: ['foo', 'type'],
+      type: 'object',
+    },
+    EntityTwo: {
+      defaultProperties: [],
+      properties: {
+        bar: {
+          type: 'string',
+        },
+        type: {
+          enum: ['TypeTwo'],
+          type: 'string',
+        },
+      },
+      required: ['bar', 'type'],
+      type: 'object',
+    },
+    EntityTypes: {
+      enum: ['TypeOne', 'TypeThree', 'TypeTwo'],
+      type: 'string',
+    },
+    Value: {
+      else: {
+        else: {
+          else: {
+            properties: {
+              number: {
+                enum: [0, 1, 2],
+                type: 'number',
+              },
+            },
+            required: ['number'],
+          },
+          if: {
+            properties: {
+              number: {
+                enum: [2],
+                type: 'number',
+              },
+            },
+            required: ['number'],
+          },
+          then: {
+            defaultProperties: [],
+            properties: {
+              baz: {
+                type: 'string',
+              },
+              number: {
+                enum: [2],
+                type: 'number',
+              },
+            },
+            required: ['baz', 'number'],
+            type: 'object',
+          },
+        },
+        if: {
+          properties: {
+            number: {
+              enum: [1],
+              type: 'number',
+            },
+          },
+          required: ['number'],
+        },
+        then: {
+          defaultProperties: [],
+          properties: {
+            bar: {
+              type: 'string',
+            },
+            number: {
+              enum: [1],
+              type: 'number',
+            },
+          },
+          required: ['bar', 'number'],
+          type: 'object',
+        },
+      },
+      if: {
+        properties: {
+          number: {
+            enum: [0],
+            type: 'number',
+          },
+        },
+        required: ['number'],
+      },
+      then: {
+        defaultProperties: [],
+        properties: {
+          foo: {
+            type: 'string',
+          },
+          number: {
+            enum: [0],
+            type: 'number',
+          },
+        },
+        required: ['foo', 'number'],
+        type: 'object',
+      },
+    },
+  },
+};
+ajv.addSchema(Schema, 'Schema');
+export function validate(
+  typeName: 'EntityTypes',
+): (value: unknown) => EntityTypes;
+export function validate(typeName: 'EntityOne'): (value: unknown) => EntityOne;
+export function validate(typeName: 'EntityTwo'): (value: unknown) => EntityTwo;
+export function validate(typeName: 'Entity'): (value: unknown) => Entity;
+export function validate(typeName: 'Value'): (value: unknown) => Value;
+export function validate(typeName: string): (value: unknown) => any {
+  const validator: any = ajv.getSchema(`Schema#/definitions/${typeName}`);
+  return (value: unknown): any => {
+    if (!validator) {
+      throw new Error(
+        `No validator defined for Schema#/definitions/${typeName}`,
+      );
+    }
+
+    const valid = validator(value);
+
+    if (!valid) {
+      throw new Error(
+        'Invalid ' +
+          typeName +
+          ': ' +
+          ajv.errorsText(
+            validator.errors!.filter((e: any) => e.keyword !== 'if'),
+            {dataVar: typeName},
+          ),
+      );
+    }
+
+    return value as any;
+  };
+}

src/Example.validator.ts

@@ -45,7 +45,10 @@ export default function validate(value: unknown): ExampleType {
     return value;
   } else {
     throw new Error(
-      ajv.errorsText(rawValidateExampleType.errors, {dataVar: 'ExampleType'}) +
+      ajv.errorsText(
+        rawValidateExampleType.errors!.filter((e: any) => e.keyword !== 'if'),
+        {dataVar: 'ExampleType'},
+      ) +
         '\n\n' +
         inspect(value),
     );

src/__tests__/build-parameters.test.ts

@@ -1,3 +1,4 @@
+jest.setTimeout(30000);
 import rimrafCB from 'rimraf';
 import {exec as execCB, ExecOptions} from 'child_process';
 import * as path from 'path';
@@ -24,6 +25,12 @@ const buildProject = async (project: string) => {
   await exec(`node ../../../lib/cli ./src/Example.ts ExampleType`, {
     cwd: testDir,
   });
+  await exec(
+    `node ../../../lib/cli ./src/DisjointUnionExample.ts --collection`,
+    {
+      cwd: testDir,
+    },
+  );
 
   await exec(`npx tsc --project ./tsconfig.json`, {
     cwd: testDir,

src/__tests__/disjointUnion.test.ts

@@ -0,0 +1,49 @@
+import {validate} from '../DisjointUnionExample.validator';
+
+// let validate: any;
+
+test('Enum Keys', () => {
+  expect(() =>
+    validate('Entity')({type: 'TypeOne'}),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"Invalid Entity: Entity should have required property 'foo'"`,
+  );
+  expect(() =>
+    validate('Entity')({type: 'TypeTwo'}),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"Invalid Entity: Entity should have required property 'bar'"`,
+  );
+  expect(() =>
+    validate('Entity')({type: 'TypeThree'}),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"Invalid Entity: Entity should have required property 'baz'"`,
+  );
+  expect(() =>
+    validate('Entity')({type: 'TypeFour'}),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"Invalid Entity: Entity.type should be equal to one of the allowed values"`,
+  );
+});
+
+test('Number Keys', () => {
+  expect(() =>
+    validate('Value')({number: 0}),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"Invalid Value: Value should have required property 'foo'"`,
+  );
+  expect(() =>
+    validate('Value')({number: 1}),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"Invalid Value: Value should have required property 'bar'"`,
+  );
+  expect(() =>
+    validate('Value')({number: 2}),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"Invalid Value: Value should have required property 'baz'"`,
+  );
+  expect(() =>
+    validate('Value')({type: 'TypeFour'}),
+  ).toThrowErrorMatchingInlineSnapshot(
+    `"Invalid Value: Value should have required property 'number'"`,
+  );
+});

src/__tests__/output/ComplexExample.validator.ts

@@ -138,7 +138,10 @@ export function validateKoaRequest(
         ctx.throw(
           400,
           'Invalid request: ' +
-            ajv.errorsText(validator.errors, {dataVar: prop}) +
+            ajv.errorsText(
+              validator.errors!.filter((e: any) => e.keyword !== 'if'),
+              {dataVar: prop},
+            ) +
             '\n\n' +
             inspect({
               params: ctx.params,
@@ -179,7 +182,10 @@ export function validate(typeName: string): (value: unknown) => any {
         'Invalid ' +
           typeName +
           ': ' +
-          ajv.errorsText(validator.errors, {dataVar: typeName}),
+          ajv.errorsText(
+            validator.errors!.filter((e: any) => e.keyword !== 'if'),
+            {dataVar: typeName},
+          ),
       );
     }