feat(minimal-blog): Add Canonical URL support

cypress/e2e/minimal-blog.ts

@@ -122,4 +122,8 @@ describe(`gatsby-theme-minimal-blog`, () => {
       .should(`have.css`, `color`, `rgb(203, 213, 224)`)
       .should(`have.css`, `background`, `rgb(26, 32, 44) none repeat scroll 0% 0% / auto padding-box border-box`)
   })
+  it(`should accept canonical url in frontmatter and set in head`, () => {
+    cy.visit(`/curses-counter-curses-and-more`).waitForRouteChange()
+    cy.get(`head link[rel='canonical']`).should(`have.attr`, `href`, `https://random-blog-about-curses.com`)
+  })
 })

examples/minimal-blog/content/posts/curses-and-counter-courses/index.mdx

@@ -2,6 +2,7 @@
 title: "Curses and Counter-curses (Bewitch Your Friends and Befuddle Your Enemies with the Latest Revenges: Hair Loss, Jelly-Legs, Tongue-Tying, and Much, Much More)"
 date: 2019-10-25
 slug: "/curses-counter-curses-and-more"
+canonicalUrl: "https://random-blog-about-curses.com"
 ---
 
 Thestral dirigible plums, Viktor Krum hexed memory charm Animagus Invisibility Cloak three-headed Dog. Half-Blood Prince Invisibility Cloak cauldron cakes, hiya Harry! Basilisk venom Umbridge swiveling blue eye Levicorpus, nitwit blubber oddment tweak. Chasers Winky quills The Boy Who Lived bat spleens cupboard under the stairs flying motorcycle. Sirius Black Holyhead Harpies, you’ve got dirt on your nose. Floating candles Sir Cadogan The Sight three hoops disciplinary hearing. Grindlewald pig’s tail Sorcerer's Stone biting teacup. Side-along dragon-scale suits Filch 20 points, Mr. Potter.

themes/gatsby-theme-minimal-blog-core/gatsby-node.js

@@ -60,6 +60,7 @@ exports.createSchemaCustomization = ({ actions, schema }, themeOptions) => {
       tags: [PostTag]
       banner: File @fileByRelativePath
       description: String
+      canonicalUrl: String
     }
 
     type PostTag {
@@ -86,6 +87,7 @@ exports.createSchemaCustomization = ({ actions, schema }, themeOptions) => {
       tags: [PostTag]
       banner: File @fileByRelativePath
       description: String
+      canonicalUrl: String
     }
 
     type MdxPage implements Node & Page {
@@ -195,6 +197,7 @@ exports.onCreateNode = ({ node, actions, getNode, createNodeId, createContentDig
       tags: modifiedTags,
       banner: node.frontmatter.banner,
       description: node.frontmatter.description,
+      canonicalUrl: node.frontmatter.canonicalUrl,
     }
 
     const mdxPostId = createNodeId(`${node.id} >>> MdxPost`)

themes/gatsby-theme-minimal-blog-core/src/templates/post-query.tsx

@@ -14,6 +14,7 @@ export const query = graphql`
         slug
       }
       description
+      canonicalUrl
       body
       excerpt
       timeToRead

themes/gatsby-theme-minimal-blog/README.md

@@ -261,10 +261,11 @@ tags:
   - Tutorial
   - Dark Arts
 banner: ./defence-against-the-dark-arts.jpg
+canonicalUrl: https://random-blog-about-curses.com/curses-counter-curses-and-more
 ---
 ```
 
-**The fields `description` and `banner` are optional!** If no description is provided, an excerpt of the blog post will be used. If no banner is provided, the default `siteImage` (from `siteMetadata`) is used.
+**The fields `description`, `banner` and `canonicalUrl` are optional!** If no description is provided, an excerpt of the blog post will be used. If no banner is provided, the default `siteImage` (from `siteMetadata`) is used. If no `canonicalUrl` is provided, it will not be included in the header.
 
 The `date` field has to be written in the format `YYYY-MM-DD`!
 

themes/gatsby-theme-minimal-blog/src/components/post.tsx

@@ -17,6 +17,7 @@ type PostProps = {
         slug: string
       }[]
       description?: string
+      canonicalUrl?: string
       body: string
       excerpt: string
       timeToRead?: number
@@ -41,6 +42,7 @@ const Post = ({ data: { post } }: PostProps) => (
       description={post.description ? post.description : post.excerpt}
       image={post.banner ? post.banner.childImageSharp.resize.src : undefined}
       pathname={post.slug}
+      canonicalUrl={post.canonicalUrl}
     />
     <Heading variant="styles.h2">{post.title}</Heading>
     <p sx={{ color: `secondary`, mt: 3, a: { color: `secondary` }, fontSize: [1, 1, 2] }}>

themes/gatsby-theme-minimal-blog/src/components/seo.tsx

@@ -9,9 +9,17 @@ type SEOProps = {
   pathname?: string
   image?: string
   children?: React.ReactNode
+  canonicalUrl?: string
 }
 
-const SEO = ({ title = ``, description = ``, pathname = ``, image = ``, children = null }: SEOProps) => {
+const SEO = ({
+  title = ``,
+  description = ``,
+  pathname = ``,
+  image = ``,
+  children = null,
+  canonicalUrl = ``,
+}: SEOProps) => {
   const site = useSiteMetadata()
 
   const {
@@ -52,6 +60,7 @@ const SEO = ({ title = ``, description = ``, pathname = ``, image = ``, children
       <link rel="icon" type="image/png" sizes="32x32" href={withPrefix(`/favicon-32x32.png`)} />
       <link rel="icon" type="image/png" sizes="16x16" href={withPrefix(`/favicon-16x16.png`)} />
       <link rel="apple-touch-icon" sizes="180x180" href={withPrefix(`/apple-touch-icon.png`)} />
+      {canonicalUrl ? <link rel="canonical" href={canonicalUrl} /> : null}
       {children}
     </Helmet>
   )