Fix extension resolution with globally installed gatsby (#102)

* Try multiple contexts when resolving extensions

* Fix GraphQL resolver bug

* Fix SSR build of exmample site

* Prettier

* Prettier with the updated version

examples/example-site/src/templates/react-blog-post.js

@@ -74,7 +74,6 @@ class BlogPostTemplate extends React.Component {
   }).Compiler;
 
   render() {
-    window.props = this.props
     const post = this.props.data.markdownRemark
     const siteTitle = this.props.data.site.siteMetadata.title
     const { previous, next } = this.props.pageContext

gatsby-node.js

@@ -77,7 +77,7 @@ async function getFromCache(type, cache, source, context, stop) {
       type: 'MarkdownRemark',
       firstOnly: true,
     });
-    return getFromCache(cache, source, context, true);
+    return getFromCache(type, cache, source, context, true);
   }
   if (!childNodes) {
     logger.error(

src/processExtension.js

@@ -1,5 +1,6 @@
 // @ts-check
 const path = require('path');
+const process = require('process');
 const logger = require('loglevel');
 const {
   getLanguageNames,
@@ -13,6 +14,7 @@ const {
 const { getHighestBuiltinLanguageId } = require('./storeUtils');
 const unzipDir = path.resolve(__dirname, '../lib/extensions');
 const requireMain = createRequire(require.main.filename);
+const requireCwd = createRequire(path.join(process.cwd(), 'index.js'));
 
 /**
  * @param {string} packageJsonPath
@@ -105,7 +107,7 @@ async function mergeCache(cache, key, value) {
  * @param {Host} host
  */
 async function getExtensionPackageJsonPath(specifier, host) {
-  const absolute = path.isAbsolute(specifier) ? specifier : requireMain.resolve(path.join(specifier, 'package.json'));
+  const absolute = path.isAbsolute(specifier) ? specifier : requireResolveExtension(specifier);
   const ext = path.extname(absolute);
   if (ext.toLowerCase() === '.vsix' || ext.toLowerCase() === '.zip') {
     const outDir = path.join(unzipDir, path.basename(absolute, ext));
@@ -137,6 +139,33 @@ async function getExtensionPackageJsonPath(specifier, host) {
   }
 }
 
+/**
+ * We want to resolve the extension from the context of the user’s gatsby-config,
+ * but this turns out to be difficult. Ideally, gatsby and this plugin are installed
+ * in the same node_modules directory as the extension, but gatsby could be invoked
+ * globally, and this plugin could be npm linked. If both of those things happen, we
+ * can also try resolving from the current working directory. One of these will
+ * probably always work.
+ * @param {string} specifier
+ */
+function requireResolveExtension(specifier) {
+  return (
+    tryResolve(require) ||
+    tryResolve(requireMain) ||
+    tryResolve(requireCwd) ||
+    require.resolve(path.join(specifier, 'package.json'))
+  ); // If none work, throw the best error stack
+
+  /** @param {NodeRequire} req */
+  function tryResolve(req) {
+    try {
+      return req.resolve(path.join(specifier, 'package.json'));
+    } catch (_) {
+      return undefined;
+    }
+  }
+}
+
 /**
  * @param {string[]} extensions
  * @param {Host} host