Provide slightly more description error on file open failure

2 files changed, 11 insertions, 1 deletions

diff --git a/lib/docx/files.js b/lib/docx/files.js
index 0e95197..6380ea4 100644
--- a/lib/docx/files.js
+++ b/lib/docx/files.js
@@ -14,7 +14,10 @@ exports.uriToPath = uriToPath;
 function Files(base) {
     function read(uri, encoding) {
         return resolveUri(uri).then(function(path) {
-            return readFile(path, encoding);
+            return readFile(path, encoding).caught(function(error) {
+                var message = "could not open external image: '" + uri + "' (document directory: '" + base + "')\n" + error.message;
+                return promises.reject(new Error(message));
+            });
         });
     }
     
diff --git a/tests/docx/files.tests.js b/tests/docx/files.tests.js
index a00b60b..65cd486 100644
--- a/tests/docx/files.tests.js
+++ b/tests/docx/files.tests.js
@@ -39,6 +39,13 @@ describe("Files", function() {
             assert.equal(err.message, "could not find external image 'not-a-real-file.png', path of input document is unknown");
         });
     });
+    
+    test("error if relative uri cannot be opened", function() {
+        var files = new Files("/tmp");
+        return assertError(files.read("not-a-real-file.png", "base64"), function(err) {
+            assert.equal(err.message, "could not open external image: 'not-a-real-file.png' (document directory: '/tmp')\nENOENT, open '/tmp/not-a-real-file.png'");
+        });
+    });
 });
 
 function assertError(promise, func) {