Nicer error for empty preview spec submission.

libpathod/app.py

@@ -82,12 +82,17 @@ def _preview(is_request):
         template = "response_preview.html"
 
     spec = request.args["spec"]
+
     args = dict(
         spec = spec,
         section = "main",
         syntaxerror = None,
         error = None
     )
+    if not spec.strip():
+        args["error"] = "Can't parse an empty spec."
+        return render(template, **args)
+
     try:
         if is_request:
             r = rparse.parse_request(app.config["pathod"].request_settings, spec)

libpathod/templates/request_preview.html

@@ -7,7 +7,6 @@
     <h2> Error: {{ syntaxerror }} </h2>
     <pre>{{ marked }}</pre>
 {% elif error %}
-    <h2> Error </h2>
     <p style="color: #ff0000">{{ error }}</p>
 {% else %}
     <h2>Spec:</h2>

libpathod/templates/response_preview.html

@@ -7,7 +7,6 @@
     <h2> Error: {{ syntaxerror }} </h2>
     <pre>{{ marked }}</pre>
 {% elif error %}
-    <h2> Error </h2>
     <p style="color: #ff0000">{{ error }}</p>
 {% else %}
     <h2>Spec:</h2>

test/test_app.py

@@ -59,3 +59,7 @@ class TestApp(tutils.DaemonTests):
         assert r.status_code == 200
         assert 'Request' in r.content
 
+        r = self.getpath("/request_preview", params=dict(spec=""))
+        assert r.status_code == 200
+        assert 'empty spec' in r.content
+