feat(templated_uri): support Option<T> fields for RFC 6570 undefined …

[kate-shine]

…values

Per RFC 6570 §2.3, template variables may be undefined. Allow Option fields in #[templated] structs to model this: None causes the variable and its associated prefix or separator to be omitted from the rendered URI, while Some(value) (including empty strings) renders normally.

Both render() and the RedactedDisplay impl are regenerated to walk the parsed template parts with __first tracking so that prefix and separator placement stays correct across all RFC 6570 operators ({x}, {+x}, {/x,y}, {?x,y}, {&x}, {;x,y}).

Includes 18 new behavioural tests covering each operator family plus a trybuild compile-fail test ensuring Option<T> still propagates the inner-type span on Escape trait-bound errors.

[Copilot]

Pull request overview

Adds RFC 6570 “undefined variable” semantics to templated_uri templates by allowing Option<T> fields in #[templated] structs, so None omits the variable (and its prefix/separator) while Some(_) renders normally. This is implemented by regenerating render() and RedactedDisplay to walk parsed template parts and track “first emitted value” per expansion group.

Changes:

• Extend macro codegen to treat Option<T> as RFC 6570 undefined values, with correct prefix/separator placement across expansion operators.
• Add behavioral tests and a trybuild compile-fail test to validate omission behavior and trait-bound error spans.
• Update crate documentation and changelogs to describe the new Option<T> feature.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/templated_uri_macros_impl/src/struct_template.rs	Main macro codegen changes: emit render() / RedactedDisplay by iterating template parts with optional-aware group handling.
crates/templated_uri_macros_impl/src/lib.rs	Updates inline snapshot tests to match the new codegen shape and adds a snapshot covering an optional field.
crates/templated_uri/tests/templated_uri.rs	Adds a large suite of behavioral tests validating Option<T> omission and separator/prefix handling.
crates/templated_uri/tests/compile_tests.rs	Registers the new trybuild compile-fail test.
crates/templated_uri/tests/ui/option_string_in_restricted_position.rs	New UI test ensuring Option<T> preserves inner-type span on Escape trait-bound errors.
crates/templated_uri/tests/ui/option_string_in_restricted_position.stderr	Expected stderr output for the new UI test.
crates/templated_uri/src/macros.rs	Documents Option<T> as RFC 6570 undefined values in #[templated] usage docs.
crates/templated_uri/src/lib.rs	Adds crate-level docs for Option<T> undefined semantics with examples.
crates/templated_uri/src/uri.rs	Minor doc/example formatting and import ordering.
crates/templated_uri/src/base_uri.rs	Minor doc/example formatting adjustments.
crates/templated_uri/src/path_and_query_template.rs	Minor doc/example import ordering and formatting.
crates/templated_uri/src/_documentation/recipes.rs	Minor doc import placement/formatting.
crates/templated_uri/examples/classified_templating.rs	Import reorganization for clarity/formatting.
crates/templated_uri/CHANGELOG.md	Adds an Unreleased feature entry for Option<T> support.
crates/templated_uri/README.md	Regenerated README to include the new Option<T> documentation section.
crates/templated_uri_macros_impl/CHANGELOG.md	Adds an Unreleased feature entry for Option<T> support.

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[codecov]

Codecov Report

❌ Patch coverage is 98.96373% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.9%. Comparing base (9bbe9d7) to head (988dddc).

Files with missing lines	Patch %	Lines
...s/templated_uri_macros_impl/src/struct_template.rs	97.8%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #408     +/-   ##
========================================
- Coverage   100.0%   99.9%   -0.1%     
========================================
  Files         227     227             
  Lines       16740   17059    +319     
========================================
+ Hits        16740   17055    +315     
- Misses          0       4      +4     

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.