Minor tidying up of the gatsby-transformer-versions-yaml plugin

plugins/gatsby-transformer-versions-yaml/create-redirects.js

@@ -2,13 +2,16 @@ const {appendFile, exists, readFile, writeFile} = require('fs-extra');
 
 const HEADER_COMMENT = `## Created with gatsby-transformer-versions-yaml`;
 
-module.exports = async function writeRedirectsFile(redirects, publicFolder) {
+// Patterned after the 'gatsby-plugin-netlify' plug-in:
+// https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-netlify/src/create-redirects.js
+module.exports = async function writeRedirectsFile(
+  redirects,
+  redirectsFilePath,
+) {
   if (!redirects.length) {
     return null;
   }
 
-  const FILE_PATH = publicFolder(`_redirects`);
-
   // Map redirect data to the format Netlify expects
   // https://www.netlify.com/docs/redirects/
   redirects = redirects.map(redirect => {
@@ -20,8 +23,7 @@ module.exports = async function writeRedirectsFile(redirects, publicFolder) {
       ...rest
     } = redirect;
 
-    // The order of the first 3 parameters is significant.
-    // The order for rest params (key-value pairs) is arbitrary.
+    // The order of these parameters is significant.
     const pieces = [
       fromPath,
       toPath,
@@ -49,9 +51,9 @@ module.exports = async function writeRedirectsFile(redirects, publicFolder) {
   // Websites may also have statically defined redirects
   // In that case we should append to them (not overwrite)
   // Make sure we aren't just looking at previous build results though
-  const fileExists = await exists(FILE_PATH);
+  const fileExists = await exists(redirectsFilePath);
   if (fileExists) {
-    const fileContents = await readFile(FILE_PATH);
+    const fileContents = await readFile(redirectsFilePath);
     if (fileContents.indexOf(HEADER_COMMENT) < 0) {
       appendToFile = true;
     }
@@ -60,6 +62,6 @@ module.exports = async function writeRedirectsFile(redirects, publicFolder) {
   const data = `${HEADER_COMMENT}\n\n${redirects.join(`\n`)}`;
 
   return appendToFile
-    ? appendFile(FILE_PATH, `\n\n${data}`)
-    : writeFile(FILE_PATH, data);
+    ? appendFile(redirectsFilePath, `\n\n${data}`)
+    : writeFile(redirectsFilePath, data);
 };

plugins/gatsby-transformer-versions-yaml/gatsby-node.js

@@ -7,26 +7,23 @@ const path = require('path');
 // Reads versions.yml data into GraphQL.
 // This is used to generate redirect rules for older documentation versions.
 exports.onPostBuild = async ({store}) => {
-  const path = resolve(__dirname, '../../content/versions.yml');
-  const file = readFileSync(path, 'utf8');
+  const versionsFile = resolve(__dirname, '../../content/versions.yml');
+  const file = readFileSync(versionsFile, 'utf8');
   const versions = safeLoad(file);
 
-  // versions.yml structure is [{title: string, path: string, url: string}, ...]
+  const {program} = store.getState();
+  const redirectsFilePath = path.join(
+    program.directory,
+    'public',
+    '_redirects',
+  );
+
+  // versions.yml structure is [{path: string, url: string, ...}, ...]
   createRedirects(
     versions.map(version => ({
       fromPath: version.path,
       toPath: version.url,
     })),
-    getPublicFolder(store),
+    redirectsFilePath,
   );
 };
-
-function buildPrefixer(prefix, ...paths) {
-  return (...subpaths) => path.join(prefix, ...paths, ...subpaths);
-}
-
-function getPublicFolder(store) {
-  const {program} = store.getState();
-
-  return buildPrefixer(program.directory, `public`);
-}