Pretter svelte-mode (#178)

Adds support for `svelte-mode` using prettier.

Co-authored-by: Radon Rosborough <radon@intuitiveexplanations.com>

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog].
 
 ## Unreleased
+### Enhancements
+* Prettier is now enabled in `svelte-mode`.
 ### Bugs fixed
 * `ktlint` would emit log messages into its stdout when formatting,
   and these would get spliced into the source file. This has been fixed

apheleia-formatters.el

@@ -54,6 +54,8 @@
      . (npx "prettier" "--stdin-filepath" filepath "--parser=ruby"))
     (prettier-scss
      . (npx "prettier" "--stdin-filepath" filepath "--parser=scss"))
+    (prettier-svelte
+     . (npx "prettier" "--stdin-filepath" filepath "--parser=svelte"))
     (prettier-typescript
      . (npx "prettier" "--stdin-filepath" filepath "--parser=typescript"))
     (prettier-yaml
@@ -178,6 +180,7 @@ rather than using this system."
     (rust-mode . rustfmt)
     (rust-ts-mode . rustfmt)
     (scss-mode . prettier-scss)
+    (svelte-mode . prettier-svelte)
     (terraform-mode . terraform)
     (TeX-latex-mode . latexindent)
     (TeX-mode . latexindent)

test/formatters/installers/prettier-svelte.bash

@@ -0,0 +1 @@
+npm install -g prettier-plugin-svelte prettier

test/formatters/samplecode/prettier-svelte/in.svelte

@@ -0,0 +1,9 @@
+<script> let attrName = "myattr"; let title = "title"; const myFunc = () => {title = "updated title";}; </script>
+<div class="foo">
+<ul class={myattr}>
+<li><a href="/">Home</a></li>
+</ul>
+</div>
+<style>
+  .foo { background: #ababab; }
+</style>

test/formatters/samplecode/prettier-svelte/out.svelte

@@ -0,0 +1,19 @@
+<script>
+  let attrName = "myattr";
+  let title = "title";
+  const myFunc = () => {
+    title = "updated title";
+  };
+</script>
+
+<div class="foo">
+  <ul class={myattr}>
+    <li><a href="/">Home</a></li>
+  </ul>
+</div>
+
+<style>
+  .foo {
+    background: #ababab;
+  }
+</style>