Fix validation stack overflow for fragment cycles inside nested fields #733
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Previously fragment cycle detection only counted fragments that are directly recursive, where the top-level selection for the fragment included a fragment spread of itself. But spreading a fragment anywhere inside a nested field is also problematic and prohibited by spec, because even if the field you're spreading into is nullable, the client can't know how deep that recursion goes, and it could be infinite. Fixes #716
SimonSapin
reviewed
Nov 9, 2023
| │ ───────┬────── | ||
| │ ╰──────── recursive fragment definition | ||
| │ | ||
| 15 │ fragment fragC on Human { name, ...fragA } | ||
| 16 │ fragment fragC on Human { name, ...fragA } | ||
| │ ────┬─── | ||
| │ ╰───── refers to itself here |
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The "refers to itself" message should probably be tweaked
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Should the diagnostic even contain a Vec of locations to show the complete cycle?
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The label is additional context for the error on the fragA definition, but I agree that it looks a bit odd. Maybe labeling every spread in the cycle and a tweaked message would be ideal?
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This is easy to do currently. would be helpful to have more context lines :/
Error: `cycle` fragment cannot reference itself
╭─[q.graphql:9:1]
│
9 │ fragment cycle on __Type {
│ ───────┬──────
│ ╰──────── recursive fragment definition
│
11 │ ...frag
│ ───┬───
│ ╰───── `cycle` references `frag` here...
│
17 │ ...cycle
│ ────┬───
│ ╰───── `frag` circularly references `cycle` here
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It would be ideal here if, in TTY formatting, cycle in the final label uses the same colour as fragment cycle in the primary label 🙈
SimonSapin
approved these changes
Nov 10, 2023
Merged
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Previously fragment cycle detection only counted fragments that are
directly recursive, where the top-level selection for the fragment
included a fragment spread of itself. But spreading a fragment anywhere
inside a nested field is also problematic and prohibited by spec,
because even if the field you're spreading into is nullable, the client
can't know how deep that recursion goes, and it could be infinite.
Fixes #716