From 250395a96a5b3ee6f2efe5d0936398fa4346e525 Mon Sep 17 00:00:00 2001
From: Joel Marcey <joelm@fb.com>
Date: Wed, 20 Dec 2017 19:47:13 -0800
Subject: [PATCH] Better error when parsing headerLinks.doc fields (#337)

Closes #309
---
 lib/core/nav/HeaderNav.js | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/lib/core/nav/HeaderNav.js b/lib/core/nav/HeaderNav.js
index f2763276b3..10db9f9d33 100644
--- a/lib/core/nav/HeaderNav.js
+++ b/lib/core/nav/HeaderNav.js
@@ -133,17 +133,25 @@ class HeaderNav extends React.Component {
           : '';
       const id = langPart + versionPart + link.doc;
       if (!Metadata[id]) {
-        if (id != link.doc) {
-          throw new Error(
-            "It looks like you've enabled language support, but haven't provided translated files. The document with id: '" +
-              id +
-              "' doesn't exist."
-          );
+        let errorStr =
+          "Processing the following `doc` field in `headerLinks` within `siteConfig.js`: '" +
+          link.doc +
+          "'";
+        if (id === link.doc) {
+          errorStr +=
+            ' It looks like there is no document with that id that exists in your docs directory. Please double check the spelling of your `doc` field and the `id` fields of your docs.';
+        } else {
+          errorStr +=
+            '. Check the spelling of your `doc` field. If that seems sane, and a document in your docs folder exists with that `id` value, \nthen this is likely a bug in Docusaurus.' +
+            ' Docusaurus thinks one or both of translations (currently set to: ' +
+            env.translation.enabled +
+            ') or versioning (currently set to: ' +
+            env.versioning.enabled +
+            ") is enabled when maybe they should not be. \nThus my internal id for this doc is: '" +
+            id +
+            "'. Please file an issue for this possible bug on GitHub.";
         }
-        throw new Error(
-          'A headerLink is specified with a document that does not exist. No document exists with id: ' +
-            link.doc
-        );
+        throw new Error(errorStr);
       }
       href = this.props.config.baseUrl + Metadata[id].permalink;
     } else if (link.page) {