errors
1-min readUpdated Sep 03, 2026
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Errors are visible, not fatal
A malformed block renders a card that names the problem. A bad chart never takes the page down, and it never fails silently either.
No rows
no rows
A path outside the content root
src escapes the content root
An unknown file type
src must end in .csv, .json, .yaml, .yml
A file that is not there
src not found: ../data/missing.json
A select path that does not exist
select path not found: by_quarter
A broken Vega-Lite spec
JSONDecodeError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)
Why this way
Three options exist for a bad block: raise, render nothing, or render the error.
Raising takes down a whole page for one typo. Rendering nothing is worse — the author ships a page with a hole in it and never learns. Rendering the error keeps the page readable and puts the message where the person who can fix it will see it.
The same rule holds for data: a src file that has moved shows a missing-file card, so the page tells you the chart is stale rather than quietly drawing an empty bar.