html_url,issue_url,id,node_id,user,user_label,created_at,updated_at,author_association,body,reactions,issue,issue_label,performed_via_github_app
https://github.com/simonw/datasette/issues/654#issuecomment-568276548,https://api.github.com/repos/simonw/datasette/issues/654,568276548,MDEyOklzc3VlQ29tbWVudDU2ODI3NjU0OA==,9599,simonw,2019-12-22T16:13:11Z,2019-12-22T16:13:11Z,OWNER,"Documentation: https://datasette.readthedocs.io/en/latest/config.html#template-debug

Demos:
* https://latest.datasette.io/?_context=1
* https://latest.datasette.io/fixtures?_context=1
* https://latest.datasette.io/fixtures/roadside_attractions?_context=1
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",541467590,Template debug mode that outputs template context,
https://github.com/simonw/datasette/issues/654#issuecomment-568274570,https://api.github.com/repos/simonw/datasette/issues/654,568274570,MDEyOklzc3VlQ29tbWVudDU2ODI3NDU3MA==,9599,simonw,2019-12-22T15:52:43Z,2019-12-22T15:52:43Z,OWNER,"One problem with this: what if secrets end up being dumped out in this debug view?

This won't happen with default Datasette but could potentially happen with a plugin.

This feature should be opt-in - maybe a `template_debug:1` config setting.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",541467590,Template debug mode that outputs template context,
https://github.com/simonw/datasette/issues/654#issuecomment-568274520,https://api.github.com/repos/simonw/datasette/issues/654,568274520,MDEyOklzc3VlQ29tbWVudDU2ODI3NDUyMA==,9599,simonw,2019-12-22T15:51:58Z,2019-12-22T15:51:58Z,OWNER,"Proof of concept:
```diff
diff --git a/datasette/views/base.py b/datasette/views/base.py
index 5182479..39d1f77 100644
--- a/datasette/views/base.py
+++ b/datasette/views/base.py
@@ -1,6 +1,7 @@
 import asyncio
 import csv
 import itertools
+import json
 import re
 import time
 import urllib
@@ -138,28 +139,31 @@ class BaseView(AsgiView):
             )
             extra_template_vars.update(extra_vars)
 
+        template_context = {
+            **context,
+            **{
+                ""app_css_hash"": self.ds.app_css_hash(),
+                ""select_templates"": select_templates,
+                ""zip"": zip,
+                ""body_scripts"": body_scripts,
+                ""extra_css_urls"": self._asset_urls(
+                    ""extra_css_urls"", template, context
+                ),
+                ""extra_js_urls"": self._asset_urls(
+                    ""extra_js_urls"", template, context
+                ),
+                ""format_bytes"": format_bytes,
+                ""database_url"": self.database_url,
+                ""database_color"": self.database_color,
+            },
+            **extra_template_vars,
+        }
+        if request.args.get(""_context""):
+            return Response.html(""<pre>{}</pre>"".format(
+                    escape(json.dumps(template_context, default=repr, indent=4))
+            ))
         return Response.html(
-            await template.render_async(
-                {
-                    **context,
-                    **{
-                        ""app_css_hash"": self.ds.app_css_hash(),
-                        ""select_templates"": select_templates,
-                        ""zip"": zip,
-                        ""body_scripts"": body_scripts,
-                        ""extra_css_urls"": self._asset_urls(
-                            ""extra_css_urls"", template, context
-                        ),
-                        ""extra_js_urls"": self._asset_urls(
-                            ""extra_js_urls"", template, context
-                        ),
-                        ""format_bytes"": format_bytes,
-                        ""database_url"": self.database_url,
-                        ""database_color"": self.database_color,
-                    },
-                    **extra_template_vars,
-                }
-            )
+            await template.render_async(template_context)
         )
 ```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",541467590,Template debug mode that outputs template context,