Addresses Copilot's round-2 review on #2035. It reported "no new comments"
but carried three *suppressed* ones; all three reproduced against the
pinned SDK.
1. The `;` path-parameter operator is absent from the SDK's operator list,
so `{;id}` parsed as a variable literally named ";id" and expanded to
nothing. Added the operator and its named expansion (`;a=1;b=2`).
2. An RFC 6570 prefix modifier was folded into the variable name: `{id:3}`
yielded a variable called "id:3" and expanded to nothing. Varspecs are
now parsed properly and the value truncated before encoding. Truncation
is by code point, since `String.prototype.slice` counts UTF-16 units and
would split an astral character into a lone surrogate.
For both of these the wrong URI is the lesser problem: a form has to
*name* the variables it asks the user to fill, so the panel was
rendering fields labelled `;id` and `id:3` that nobody could use.
3. Requiredness was applied per variable, but it is a property of the
*expression*: RFC 6570 drops undefined names from a multi-name
expression, so `{a,b}` with only `a` filled expands to `a`'s value --
the SDK does this too. The panel was refusing input the expander would
have accepted. `hasRequiredValues` now encodes "any one name in a
required group suffices", and such a field reads "Any one of: a, b"
rather than falsely claiming each is mandatory.
Two structural consequences, each pinned by a test:
- Takeover is now per TEMPLATE rather than per expression. Splicing
corrected fragments into a template the SDK re-expands would leave its
cross-expression `?`-to-`&` rewrite blind to the fragments already
resolved.
- Expansion is split into a strict variant that throws and a lenient one
that returns the raw template. `readResourceFromTemplate` wraps the
thrown error with the template name -- three pre-existing integration
tests assert that -- while the form must not throw on a server-supplied
template, since that would take out the panel on render. The strict
variant constructs the SDK template unconditionally, because that
construction is what validates syntax: otherwise `x://{;a}{b,c` would
take the own-expansion path and its unclosed tail would pass as literal
text with nothing objecting.
Signed-off-by: cliffhall <cliff@futurescale.com>
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