Tags can now be deleted.

examples/realworld/README.md

@@ -17,9 +17,6 @@ Todo:
 - [x] For Article, use special id which contains title in the name, and display it in url?
 - [x] CR*D Comments on articles.
 - [x] Add tags to articles.
-- [ ] Make article tags deleteable. Right now I have something but it does not delete them from the database!
-      I think I am using Prisma wrong here, the problem is probably in connectOrCreate when updating,
-      it does not seem to delete the ones that are missing now.
 - [ ] Show Popular Tags on home page.
 - [ ] Favorite articles.
 - [ ] Following other users.

examples/realworld/ext/actions.js

@@ -61,19 +61,29 @@ export const updateArticle = async ({ id, title, description, markdownContent, t
 
   // TODO: Nicer error handling! Right now everything is returned as 500 while it could be instead
   //   useful error message about username being taken / not unique, and other validation errors.
-  if (!await context.entities.Article.findFirst({
-    where: { id, user: { id: context.user.id }} // TODO: This line is not fun to write.
-  })) {
+
+  const article = await context.entities.Article.findFirst({
+    where: { id, user: { id: context.user.id }}, // TODO: This line is not fun to write.
+    include: { tags: true }
+  })
+  if (!article) {
     throw new HttpError(404)
   }
 
+  const subtractTags = (tags1, tags2) => tags1.filter(t1 => !tags2.find(t2 => t2.name === t1.name))
+  const tagsToAdd = tags ? subtractTags(tags, article.tags) : []
+  const tagsToRemove = tags ? subtractTags(article.tags, tags) : []
+
   await context.entities.Article.update({
     where: { id },
     data: {
       title,
       description,
       markdownContent,
-      tags: { connectOrCreate: tags.map(tag => ({ where: tag, create: tag })) }
+      tags: {
+        connectOrCreate: tagsToAdd.map(tag => ({ where: tag, create: tag })),
+        disconnect: tagsToRemove
+      }
     }
   })
 }