kbn-config-schema: allow parsing of array and object types from string

packages/kbn-config-schema/README.md

@@ -227,6 +227,9 @@ __Usage:__
 const valueSchema = schema.arrayOf(schema.number());
 ```
 
+__Notes:__
+* The `schema.arrayOf()` also supports a json string as input if it can be safely parsed using `JSON.parse` and if the resulting value is an array.
+
 #### `schema.object()`
 
 Validates input data as an object with a predefined set of properties.
@@ -249,6 +252,7 @@ const valueSchema = schema.object({
 __Notes:__
 * Using `allowUnknowns` is discouraged and should only be used in exceptional circumstances. Consider using `schema.recordOf()` instead.
 * Currently `schema.object()` always has a default value of `{}`, but this may change in the near future. Try to not rely on this behaviour and specify default value explicitly or use `schema.maybe()` if the value is optional.
+* `schema.object()` also supports a json string as input if it can be safely parsed using `JSON.parse` and if the resulting value is a plain object.
 
 #### `schema.recordOf()`
 
@@ -267,6 +271,7 @@ const valueSchema = schema.recordOf(schema.string(), schema.number());
 
 __Notes:__
 * You can use a union of literal types as a record's key schema to restrict record to a specific set of keys, e.g. `schema.oneOf([schema.literal('isEnabled'), schema.literal('name')])`.
+* `schema.recordOf()` also supports a json string as input if it can be safely parsed using `JSON.parse` and if the resulting value is a plain object.
 
 #### `schema.mapOf()`
 
@@ -283,6 +288,10 @@ __Usage:__
 const valueSchema = schema.mapOf(schema.string(), schema.number());
 ```
 
+__Notes:__
+* You can use a union of literal types as a record's key schema to restrict record to a specific set of keys, e.g. `schema.oneOf([schema.literal('isEnabled'), schema.literal('name')])`.
+* `schema.mapOf()` also supports a json string as input if it can be safely parsed using `JSON.parse` and if the resulting value is a plain object.
+
 ### Advanced types
 
 #### `schema.oneOf()`

packages/kbn-config-schema/src/internals/index.ts

@@ -250,22 +250,47 @@ export const internals = Joi.extend([
 
     base: Joi.object(),
     coerce(value: any, state: State, options: ValidationOptions) {
-      // If value isn't defined, let Joi handle default value if it's defined.
-      if (value !== undefined && !isPlainObject(value)) {
-        return this.createError('object.base', { value }, state, options);
+      if (value === undefined || isPlainObject(value)) {
+        return value;
       }
 
-      return value;
+      if (options.convert && typeof value === 'string') {
+        try {
+          const parsed = JSON.parse(value);
+          if (isPlainObject(parsed)) {
+            return parsed;
+          }
+          return this.createError('object.base', { value: parsed }, state, options);
+        } catch (e) {
+          return this.createError('object.parse', { value }, state, options);
+        }
+      }
+
+      return this.createError('object.base', { value }, state, options);
     },
     rules: [anyCustomRule],
   },
   {
     name: 'map',
 
     coerce(value: any, state: State, options: ValidationOptions) {
+      if (value === undefined) {
+        return value;
+      }
       if (isPlainObject(value)) {
         return new Map(Object.entries(value));
       }
+      if (options.convert && typeof value === 'string') {
+        try {
+          const parsed = JSON.parse(value);
+          if (isPlainObject(parsed)) {
+            return new Map(Object.entries(parsed));
+          }
+          return this.createError('map.base', { value: parsed }, state, options);
+        } catch (e) {
+          return this.createError('map.parse', { value }, state, options);
+        }
+      }
 
       return value;
     },
@@ -321,11 +346,23 @@ export const internals = Joi.extend([
   {
     name: 'record',
     pre(value: any, state: State, options: ValidationOptions) {
-      if (!isPlainObject(value)) {
-        return this.createError('record.base', { value }, state, options);
+      if (value === undefined || isPlainObject(value)) {
+        return value;
       }
 
-      return value as any;
+      if (options.convert && typeof value === 'string') {
+        try {
+          const parsed = JSON.parse(value);
+          if (isPlainObject(parsed)) {
+            return parsed;
+          }
+          return this.createError('record.base', { value: parsed }, state, options);
+        } catch (e) {
+          return this.createError('record.parse', { value }, state, options);
+        }
+      }
+
+      return this.createError('record.base', { value }, state, options);
     },
     rules: [
       anyCustomRule,
@@ -371,12 +408,23 @@ export const internals = Joi.extend([
 
     base: Joi.array(),
     coerce(value: any, state: State, options: ValidationOptions) {
-      // If value isn't defined, let Joi handle default value if it's defined.
-      if (value !== undefined && !Array.isArray(value)) {
-        return this.createError('array.base', { value }, state, options);
+      if (value === undefined || Array.isArray(value)) {
+        return value;
       }
 
-      return value;
+      if (options.convert && typeof value === 'string') {
+        try {
+          const parsed = JSON.parse(value);
+          if (Array.isArray(parsed)) {
+            return parsed;
+          }
+          return this.createError('array.base', { value: parsed }, state, options);
+        } catch (e) {
+          return this.createError('array.parse', { value }, state, options);
+        }
+      }
+
+      return this.createError('array.base', { value }, state, options);
     },
     rules: [anyCustomRule],
   },

packages/kbn-config-schema/src/types/array_type.test.ts

@@ -24,29 +24,65 @@ test('returns value if it matches the type', () => {
   expect(type.validate(['foo', 'bar', 'baz'])).toEqual(['foo', 'bar', 'baz']);
 });
 
+test('properly parse the value if input is a string', () => {
+  const type = schema.arrayOf(schema.string());
+  expect(type.validate('["foo", "bar", "baz"]')).toEqual(['foo', 'bar', 'baz']);
+});
+
 test('fails if wrong input type', () => {
   const type = schema.arrayOf(schema.string());
-  expect(() => type.validate('test')).toThrowErrorMatchingSnapshot();
+  expect(() => type.validate(12)).toThrowErrorMatchingInlineSnapshot(
+    `"expected value of type [array] but got [number]"`
+  );
+});
+
+test('fails if string input cannot be parsed', () => {
+  const type = schema.arrayOf(schema.string());
+  expect(() => type.validate('test')).toThrowErrorMatchingInlineSnapshot(
+    `"could not parse array value from [test]"`
+  );
+});
+
+test('fails with correct type if parsed input is not an array', () => {
+  const type = schema.arrayOf(schema.string());
+  expect(() => type.validate('{"foo": "bar"}')).toThrowErrorMatchingInlineSnapshot(
+    `"expected value of type [array] but got [Object]"`
+  );
 });
 
 test('includes namespace in failure when wrong top-level type', () => {
   const type = schema.arrayOf(schema.string());
-  expect(() => type.validate('test', {}, 'foo-namespace')).toThrowErrorMatchingSnapshot();
+  expect(() => type.validate('test', {}, 'foo-namespace')).toThrowErrorMatchingInlineSnapshot(
+    `"[foo-namespace]: could not parse array value from [test]"`
+  );
 });
 
 test('includes namespace in failure when wrong item type', () => {
   const type = schema.arrayOf(schema.string());
-  expect(() => type.validate([123], {}, 'foo-namespace')).toThrowErrorMatchingSnapshot();
+  expect(() => type.validate([123], {}, 'foo-namespace')).toThrowErrorMatchingInlineSnapshot(
+    `"[foo-namespace.0]: expected value of type [string] but got [number]"`
+  );
 });
 
 test('fails if wrong type of content in array', () => {
   const type = schema.arrayOf(schema.string());
-  expect(() => type.validate([1, 2, 3])).toThrowErrorMatchingSnapshot();
+  expect(() => type.validate([1, 2, 3])).toThrowErrorMatchingInlineSnapshot(
+    `"[0]: expected value of type [string] but got [number]"`
+  );
+});
+
+test('fails when parsing if wrong type of content in array', () => {
+  const type = schema.arrayOf(schema.string());
+  expect(() => type.validate('[1, 2, 3]')).toThrowErrorMatchingInlineSnapshot(
+    `"[0]: expected value of type [string] but got [number]"`
+  );
 });
 
 test('fails if mixed types of content in array', () => {
   const type = schema.arrayOf(schema.string());
-  expect(() => type.validate(['foo', 'bar', true, {}])).toThrowErrorMatchingSnapshot();
+  expect(() => type.validate(['foo', 'bar', true, {}])).toThrowErrorMatchingInlineSnapshot(
+    `"[2]: expected value of type [string] but got [boolean]"`
+  );
 });
 
 test('returns empty array if input is empty but type has default value', () => {
@@ -61,7 +97,9 @@ test('returns empty array if input is empty even if type is required', () => {
 
 test('fails for null values if optional', () => {
   const type = schema.arrayOf(schema.maybe(schema.string()));
-  expect(() => type.validate([null])).toThrowErrorMatchingSnapshot();
+  expect(() => type.validate([null])).toThrowErrorMatchingInlineSnapshot(
+    `"[0]: expected value of type [string] but got [null]"`
+  );
 });
 
 test('handles default values for undefined values', () => {
@@ -108,7 +146,9 @@ test('object within array with required', () => {
 
   const value = [{}];
 
-  expect(() => type.validate(value)).toThrowErrorMatchingSnapshot();
+  expect(() => type.validate(value)).toThrowErrorMatchingInlineSnapshot(
+    `"[0.foo]: expected value of type [string] but got [undefined]"`
+  );
 });
 
 describe('#minSize', () => {
@@ -119,7 +159,7 @@ describe('#minSize', () => {
   test('returns error when fewer items', () => {
     expect(() =>
       schema.arrayOf(schema.string(), { minSize: 2 }).validate(['foo'])
-    ).toThrowErrorMatchingSnapshot();
+    ).toThrowErrorMatchingInlineSnapshot(`"array size is [1], but cannot be smaller than [2]"`);
   });
 });
 
@@ -131,6 +171,6 @@ describe('#maxSize', () => {
   test('returns error when more items', () => {
     expect(() =>
       schema.arrayOf(schema.string(), { maxSize: 1 }).validate(['foo', 'bar'])
-    ).toThrowErrorMatchingSnapshot();
+    ).toThrowErrorMatchingInlineSnapshot(`"array size is [2], but cannot be greater than [1]"`);
   });
 });

packages/kbn-config-schema/src/types/array_type.ts

@@ -49,6 +49,8 @@ export class ArrayType<T> extends Type<T[]> {
       case 'any.required':
       case 'array.base':
         return `expected value of type [array] but got [${typeDetect(value)}]`;
+      case 'array.parse':
+        return `could not parse array value from [${value}]`;
       case 'array.min':
         return `array size is [${value.length}], but cannot be smaller than [${limit}]`;
       case 'array.max':