Addresses Copilot's round-18 review on #2035. Two suppressed comments, both
holes in my own recent fixes rather than in the original code.
1. Round 16's grouping keyed off the length-announcing lead byte alone, so
it accepted sequences RFC 3629 forbids -- and the comment claiming they
fell back to per-triplet counting was simply wrong. Measured on 05bbfe50:
x{+v:1} "%C0%80x" => "x%C0%80" overlong
"%E0%80%80x" => "x%E0%80%80" overlong
"%ED%A0%80x" => "x%ED%A0%80" UTF-16 surrogate
"%F4%90%80%80x" => "x%F4%90%80%80" past U+10FFFF
The lead-byte ranges are now the well-formed ones -- C2-DF, E0 only with
A0-BF, ED only with 80-9F, F0 only with 90-BF, F4 only with 80-8F -- so
each of the above falls back to one triplet, which is what the fallback
was always documented to do. The legal boundary cases (%E0%A0%80,
%ED%9F%BF, %F4%8F%BF%BF) are tested alongside, so tightening the ranges
cannot quietly start splitting valid characters.
2. The preview never ran the read's template validation. It expands
expression by expression, so `x://{a}}/{b}` with both fields filled
previewed `x://1}/2` -- a URI whose stray `}` makes every read refuse.
Validation moved into an exported `templateError` that both callers
consult, so they cannot drift. It subsumes the narrower rule round 12
added here ("leave the invalid part standing"), which still let the REST
of such a template expand: the refusal is per template, not per
expression, so the preview now shows the template verbatim -- literals
unencoded included, since half-normalizing an unreadable template invents
a string the server never published. Two existing tests asserted the
weaker behavior and now assert this one.
npm run ci passes.
Signed-off-by: cliffhall <cliff@futurescale.com>
9caac43da4