Struct PlaceholderRefusal 

#[non_exhaustive]
pub struct PlaceholderRefusal {
    pub param: String,
    pub rule: &'static str,
    pub expected: String,
}

The D4 path-placeholder floor, re-exported from core pmcp.

There is exactly ONE implementation of these rules and it lives in pmcp::server::schema_validation. This is a pub use, never a second copy (Phase 128, Q2). Two reasons the home is core rather than here:

1. The toolkit’s curated http build has no pmcp-code-mode edge and must not gain one (SC-1), so the shared rule cannot live in this crate.
2. This repo has a documented three-way-drift incident from a security rule that existed in more than one copy, so a second denylist is a prohibited shape rather than a style preference.

The re-export exists because D-09 obliges the SDK to publish the helper under the name a third-party HttpExecutor implementor would look for. An implementor whose template syntax is not OpenAPI’s {key} can call pmcp_code_mode::validate_path_placeholder on each value it substitutes and pmcp_code_mode::validate_resolved_path on the composed result — or pmcp_code_mode::validate_resolved_target, which is that rule widened by the single author-written ? separator, and is what ResolvedPath::from_checked itself calls. Either reaches the same rule the SDK itself applies before calling HttpExecutor::execute_request. (Plain backticks, not an intra-doc link: executor is gated on js-runtime and the link would not resolve in a default-feature doc build.) Why a path-placeholder value was refused.

Carries the DECLARED parameter name and the DECLARED expectation only — never a byte of the rejected value, and never which character tripped the floor (naming the character would itself echo a byte of the value and turn the refusal into a one-byte oracle).

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

param: String

The DECLARED parameter name, safe to echo.

rule: &'static str

Which rule refused: "nonEmpty", "percentEncoding", "characterFloor", "maxLength", "pattern", "segmentMaxLength" or "pathSegment".

expected: String

The DECLARED expectation, rendered value-free.

Trait Implementations

impl Clone for PlaceholderRefusal

fn clone(&self) -> PlaceholderRefusal

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PlaceholderRefusal

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Display for PlaceholderRefusal

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Renders in the render_scalar house style (PATTERNS SP-1): name the parameter, state the declared expectation, never the value.

impl Error for PlaceholderRefusal

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.