refactor: unify how validateOptions is handled (#6961)

* refactor: unify how validateOptions is handled

* fix types

* fix again

packages/docusaurus-plugin-content-blog/src/frontMatter.ts

@@ -0,0 +1,81 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {
+  JoiFrontMatter as Joi, // Custom instance for front matter
+  URISchema,
+  validateFrontMatter,
+  FrontMatterTagsSchema,
+  FrontMatterTOCHeadingLevels,
+} from '@docusaurus/utils-validation';
+import type {BlogPostFrontMatter} from '@docusaurus/plugin-content-blog';
+
+const BlogPostFrontMatterAuthorSchema = Joi.object({
+  key: Joi.string(),
+  name: Joi.string(),
+  title: Joi.string(),
+  url: URISchema,
+  imageURL: Joi.string(),
+})
+  .or('key', 'name', 'imageURL')
+  .rename('image_url', 'imageURL', {alias: true});
+
+const FrontMatterAuthorErrorMessage =
+  '{{#label}} does not look like a valid blog post author. Please use an author key or an author object (with a key and/or name).';
+
+const BlogFrontMatterSchema = Joi.object<BlogPostFrontMatter>({
+  id: Joi.string(),
+  title: Joi.string().allow(''),
+  description: Joi.string().allow(''),
+  tags: FrontMatterTagsSchema,
+  draft: Joi.boolean(),
+  date: Joi.date().raw(),
+
+  // New multi-authors front matter:
+  authors: Joi.alternatives()
+    .try(
+      Joi.string(),
+      BlogPostFrontMatterAuthorSchema,
+      Joi.array()
+        .items(Joi.string(), BlogPostFrontMatterAuthorSchema)
+        .messages({
+          'array.sparse': FrontMatterAuthorErrorMessage,
+          'array.includes': FrontMatterAuthorErrorMessage,
+        }),
+    )
+    .messages({
+      'alternatives.match': FrontMatterAuthorErrorMessage,
+    }),
+  // Legacy author front matter
+  author: Joi.string(),
+  author_title: Joi.string(),
+  author_url: URISchema,
+  author_image_url: URISchema,
+  // TODO enable deprecation warnings later
+  authorURL: URISchema,
+  // .warning('deprecate.error', { alternative: '"author_url"'}),
+  authorTitle: Joi.string(),
+  // .warning('deprecate.error', { alternative: '"author_title"'}),
+  authorImageURL: URISchema,
+  // .warning('deprecate.error', { alternative: '"author_image_url"'}),
+
+  slug: Joi.string(),
+  image: URISchema,
+  keywords: Joi.array().items(Joi.string().required()),
+  hide_table_of_contents: Joi.boolean(),
+
+  ...FrontMatterTOCHeadingLevels,
+}).messages({
+  'deprecate.error':
+    '{#label} blog frontMatter field is deprecated. Please use {#alternative} instead.',
+});
+
+export function validateBlogPostFrontMatter(
+  frontMatter: Record<string, unknown>,
+): BlogPostFrontMatter {
+  return validateFrontMatter(frontMatter, BlogFrontMatterSchema);
+}