feat(example): add public API end-to-end flow

Cargo.lock

@@ -270,9 +270,11 @@ name = "wip-protocol"
 version = "0.1.0"
 
 [[package]]
-name = "wip-rs"
+name = "wip-public-api-example"
 version = "0.1.0"
 dependencies = [
+ "wip-host",
+ "wip-interface",
  "wip-protocol",
 ]
 

Cargo.toml

@@ -9,9 +9,14 @@ members = [
 resolver = "3"
 
 [package]
-name = "wip-rs"
+name = "wip-public-api-example"
 version = "0.1.0"
 edition = "2024"
+description = "End-to-end example of the public WIP Rust APIs"
+license = "MIT OR Apache-2.0"
+publish = false
 
 [dependencies]
+wip-host = { path = "crates/wip-host" }
+wip-interface = { path = "crates/wip-interface" }
 wip-protocol = { path = "crates/wip-protocol" }

README.md

@@ -2,6 +2,65 @@
 
 Rust building blocks for the Web Interface Protocol (WIP).
 
+The repository currently provides a transport-independent protocol model, a
+Rust interface-authoring facade, and a request-scoped host runtime. HTTP and
+other transport bindings are intentionally outside the supported slice.
+
+## Crate graph and responsibilities
+
+```text
+wip-public-api-example (workspace-only executable, integration tests, doctest)
+├── wip-protocol              logical declarations, values, calls, and validation
+├── wip-interface             application DTO codecs and interface authoring facade
+│   ├── wip-protocol
+│   └── wip-interface-macros  proc-macro implementation detail
+└── wip-host                  descriptor registry, publication, and qualified dispatch
+    ├── wip-interface
+    └── wip-protocol
+```
+
+| Crate | Responsibility | Does not own |
+| --- | --- | --- |
+| `wip-protocol` | Transport-independent descriptors, object/call/result types, logical `Value`s, validation, and stable protocol error categories. | Application DTOs, implementations, persistence, or wire encoding. |
+| `wip-interface` | The public `WipType`/`interface` authoring API, Rust-to-protocol codecs, generated descriptors, and typed implementation dispatch. | Object publication, backend lifetime, or transport policy. |
+| `wip-interface-macros` | Procedural-macro expansion used by `wip-interface`. It is not an application dependency. | A supported direct user API. |
+| `wip-host` | Opaque interface registration, explicit object membership, validator checks, and interface-qualified dispatch against one host-owned instance. | Backend atomicity, global object lookup, or network serving. |
+| `wip-public-api-example` | An independently compiled consumer of only the three public crates. Its DTOs and traits are application-owned; its implementation and backend handle remain host-private. | Reusable library API or a production server. |
+
+The boundary is intentional: protocol types describe what can cross a
+transport; application DTOs opt into that model with `WipType`; a host-private
+implementation owns credentials, handles, and backend state; and a future
+transport maps its own routes/envelopes to `OperationCall`/`OperationResult`
+without placing transport-specific types in descriptors or application traits.
+
+## End-to-end example
+
+[`src/lib.rs`](src/lib.rs) is the complete public-API example and
+[`src/main.rs`](src/main.rs) runs it. It demonstrates all of the following:
+
+1. public application DTOs derived as `WipType` records and unions;
+2. two public traits declared with `#[wip::interface]`;
+3. a private host struct implementing both traits;
+4. explicit publication of both interfaces on one object;
+5. registry observation and validation of generated descriptors;
+6. calls made with interface references, operation names, and `Value` arguments;
+7. validated result values decoded back to the typed application result;
+8. independent dispatch of the same `status` operation name on both interfaces;
+9. a domain rejection returned as data and a backend failure returned as a host
+   error.
+
+Run it inside the development shell:
+
+```console
+nix develop
+cargo run --package wip-public-api-example
+```
+
+The normal integration test is in [`tests/end_to_end.rs`](tests/end_to_end.rs).
+Unit tests beside the example additionally cover every host dispatch failure,
+invalid arguments and results, interface membership, validators, and
+same-named operations.
+
 ## Interface authoring
 
 Applications depend on `wip-interface`, normally imported as `wip`:
@@ -30,12 +89,31 @@ pub trait Messenger {
 ```
 
 The `interface` attribute and `WipType` derive are re-exported by the facade;
-users do not import `wip-interface-macros` directly. The generated
+users do not import `wip-interface-macros` or generated private support symbols.
-`MessengerDefinition` constructs an `InterfaceDescriptor`, decodes named
+The generated `MessengerDefinition` constructs an `InterfaceDescriptor`,
-arguments, encodes results, validates both boundaries, and provides typed
+decodes named arguments, encodes results, validates both boundaries, and
-dispatch for any `T: Messenger`.
+provides typed dispatch for any `T: Messenger`.
 
-### Type mapping
+### Supported Rust syntax
+
+A supported interface is a public, non-generic trait containing methods with:
+
+- exactly an immutable `&self` receiver;
+- simple named, owned parameters;
+- an explicit `wip::OperationResult<T>` return;
+- `()` only as the application return when no value is produced; and
+- direct `Option<T>` only for an omittable parameter.
+
+`WipType` derives support named-field structs, all-unit enums, and enums whose
+variants each contain exactly one unnamed payload. The macros reject private,
+generic, inherited, unsafe, auto, or associated-item traits; const, async,
+unsafe, extern, variadic, generic, default-bodied, or non-`&self` methods;
+borrowed/custom-lifetime values; tuple/unit/generic structs; Rust unions;
+mixed/named-field enum variants; explicit discriminants; nested `Option`; and
+`Option` in returns, collections, entries, or union payloads. These diagnostics
+are compile-fail tested under `crates/wip-interface/tests/ui`.
+
+### Rust type mapping
 
 | Rust | Protocol |
 | --- | --- |
@@ -45,27 +123,21 @@ dispatch for any `T: Messenger`.
 | `f32`, `f64` | finite number |
 | `String` | string |
 | `wip::Bytes` | bytes |
-| `wip::wip_protocol::JsonValue` | JSON |
+| `wip::JsonValue` | JSON |
 | `wip::Entry<K, V>` | entry |
 | `Vec<T>` | list |
 | named-field `#[derive(wip::WipType)]` struct | named record |
 | all-unit `#[derive(wip::WipType)]` enum | named enum |
 | all-newtype `#[derive(wip::WipType)]` enum | named tagged union |
 
-`Option<T>` is accepted only for a direct DTO field or operation parameter and
+`Option<T>` means that a direct DTO field or operation parameter may be
-means that the named value may be omitted. It is not protocol null. Domain
+omitted; it is not protocol null. JSON null remains available inside
-failures are modeled in the application result (usually a derived union) and
+`wip::JsonValue`.
-returned through `Ok`; `wip::HostError` is only for host/runtime failures.
 
 Rust doc comments become descriptor metadata. For an operation, a `# Returns`
 section documents the return declaration; text before that section documents
 the operation itself.
 
-The supported interface slice is deliberately non-generic: public traits,
-`&self`, named parameters, and `OperationResult<T>`. Generic traits or methods,
-associated items, custom lifetimes, inheritance, default method bodies, and
-other receiver forms are rejected at their source spans.
-
 ## Host publication and dispatch
 
 Applications use `wip-host` to register generated definitions and explicitly
@@ -84,16 +156,38 @@ let protocol_object = published.protocol_object();
 interface trait. Implementing a trait does not expose it automatically, empty
 interface sets are valid, insertion order is preserved, and duplicate
 references are rejected. Registry references are opaque; descriptor names and
-Rust type names are not used as wire identity.
+Rust type names are not used as independent wire identity.
 
-Dispatch is qualified by interface reference and operation name. The host checks
+Dispatch is qualified by interface reference and operation name. The host
-current object identity and validator policy, current interface membership,
+checks current object identity and validator policy, current interface
-interface validator, descriptor operation, arguments, and result while retaining
+membership, interface validator, descriptor operation, arguments, and result
-the selected object and registered artifact. Host-private fields and backend
+while retaining the selected object and registered artifact. Host-private
-handles are never projected by `WipObject`.
+fields and backend handles are never projected by `WipObject`.
+
+Application domain failures belong in a derived result union and are returned
+through `Ok`. `wip::HostError` is reserved for runtime/backend failures. Invalid
+arguments are rejected before invocation; malformed encoded results are
+rejected as internal host failures and never returned as application data.
 
 Providers remain responsible for backend atomicity. Enter a transaction, lock,
 stable-handle scope, or conditional-update primitive before constructing and
 dispatching the request-scoped `PublishedObject`, and retain it until dispatch
 returns. The runtime never validates one object and then resolves a second
 snapshot, but it cannot make an arbitrary external backend atomic by itself.
+
+## Validation
+
+Enter the dev shell and run the acceptance commands exactly:
+
+```console
+nix develop
+cargo fmt --all -- --check
+cargo check --workspace --all-targets
+cargo test --workspace --all-targets
+cargo clippy --workspace --all-targets -- -D warnings
+```
+
+`cargo test --workspace --all-targets` includes the public example integration
+test, runtime failure tests, and `trybuild` compile-fail suites. Run
+`cargo test --workspace --doc` when validating the checked rustdoc examples
+separately.

src/lib.rs

@@ -0,0 +1,627 @@
+//! End-to-end use of the public WIP protocol, interface, and host APIs.
+//!
+//! This workspace package is deliberately separate from the three library
+//! crates. It defines application DTOs and interfaces with `wip-interface`,
+//! keeps its implementation private, publishes that implementation with
+//! `wip-host`, and crosses the call boundary only with `wip-protocol` values.
+//!
+//! The complete scenario can be run as a normal binary or called directly:
+//!
+//! ```
+//! let report = wip_public_api_example::run()?;
+//!
+//! assert_eq!(report.published_interfaces.len(), 2);
+//! assert_eq!(report.catalog_status, "catalog-ready");
+//! assert_eq!(report.audit_status, "audit-ready");
+//! assert_eq!(
+//!     report.host_failure,
+//!     wip_host::CallErrorKind::Implementation,
+//! );
+//! # Ok::<(), Box<dyn std::error::Error>>(())
+//! ```
+
+#![deny(missing_docs)]
+
+use std::error::Error;
+use std::io;
+
+use wip_host::{
+    CallErrorKind, CallRequest, InterfaceRef, InterfaceRegistry, InterfaceTarget, PublishedObject,
+    Validator, WipObject,
+};
+use wip_interface as wip;
+use wip_interface::WipType;
+use wip_protocol::{
+    InterfaceObservation, NamedValue, ObjectId, OperationOutcome, OperationResult, OperationTarget,
+};
+
+const OBJECT_ID: &str = "article-service";
+const OBJECT_VALIDATOR: &[u8] = b"object-v1";
+const CATALOG_VALIDATOR: &[u8] = b"catalog-v1";
+
+/// An application-owned request DTO mapped to a protocol record.
+#[derive(Debug, Clone, PartialEq, Eq, wip::WipType)]
+pub struct PublishRequest {
+    /// Title of the article to publish.
+    pub title: String,
+    /// Optional article body; omission is distinct from JSON null.
+    pub body: Option<String>,
+}
+
+/// The application domain result of a publication attempt.
+///
+/// Rejection is an ordinary typed result. It is intentionally distinct from a
+/// host or backend failure, which uses [`wip::HostError`].
+#[derive(Debug, Clone, PartialEq, Eq, wip::WipType)]
+pub enum PublishOutcome {
+    /// Publication succeeded and returned its application identifier.
+    Published(String),
+    /// An application policy rejected the publication.
+    Rejected(String),
+}
+
+/// Article publication operations.
+#[wip::interface]
+pub trait Catalog {
+    /// Publishes an article or reports an application-domain rejection.
+    ///
+    /// # Returns
+    /// The typed application outcome.
+    fn publish(
+        &self,
+        /// Application publication request.
+        request: PublishRequest,
+    ) -> wip::OperationResult<PublishOutcome>;
+
+    /// Returns the catalog-qualified status.
+    ///
+    /// # Returns
+    /// A catalog status label.
+    fn status(&self) -> wip::OperationResult<String>;
+
+    /// Demonstrates a host/backend failure rather than a domain result.
+    ///
+    /// # Returns
+    /// A backend status only when the host can reach it.
+    fn backend_status(&self) -> wip::OperationResult<String>;
+}
+
+/// Audit operations exposed by the same object.
+#[wip::interface]
+pub trait Audit {
+    /// Returns the audit-qualified status.
+    ///
+    /// This deliberately has the same operation name as [`Catalog::status`].
+    ///
+    /// # Returns
+    /// An audit status label.
+    fn status(&self) -> wip::OperationResult<String>;
+}
+
+/// A registered but deliberately unexposed interface used to demonstrate that
+/// Rust trait implementation does not imply protocol membership.
+#[wip::interface]
+pub trait Diagnostics {
+    /// Returns host-private diagnostics when the interface is explicitly exposed.
+    ///
+    /// # Returns
+    /// A diagnostic label.
+    fn diagnostics(&self) -> wip::OperationResult<String>;
+}
+
+/// Observable outcomes from the complete public-API scenario.
+#[derive(Debug, Clone, PartialEq)]
+pub struct DemoReport {
+    /// Opaque interface references published by the object, in exposure order.
+    pub published_interfaces: Vec<String>,
+    /// Descriptor identity observed for the catalog interface.
+    pub catalog_descriptor: String,
+    /// Descriptor identity observed for the audit interface.
+    pub audit_descriptor: String,
+    /// Typed successful application result decoded from a validated `Value`.
+    pub published: PublishOutcome,
+    /// Typed application-domain rejection decoded from a validated `Value`.
+    pub rejected: PublishOutcome,
+    /// Result of the catalog-qualified `status` operation.
+    pub catalog_status: String,
+    /// Result of the audit-qualified `status` operation.
+    pub audit_status: String,
+    /// Stable failure kind produced by the deliberate host/backend failure.
+    pub host_failure: CallErrorKind,
+    /// A protocol-level operation result built from the host failure.
+    pub protocol_failure: OperationResult,
+}
+
+/// Runs the complete end-to-end example.
+///
+/// The function registers and observes generated descriptors, explicitly
+/// exposes two interfaces on one host-private object, validates the resulting
+/// protocol observation, dispatches interface-qualified calls using named
+/// [`wip_protocol::Value`] arguments, decodes validated values back to
+/// application types, and keeps a domain rejection distinct from a host
+/// failure.
+///
+/// # Errors
+///
+/// Returns an error if registration, publication, observation validation,
+/// dispatch, or application-value decoding fails unexpectedly.
+pub fn run() -> Result<DemoReport, Box<dyn Error>> {
+    let mut registry = InterfaceRegistry::new();
+    let catalog = registry.register(CatalogDefinition, Some(Validator::new(CATALOG_VALIDATOR)))?;
+    let audit = registry.register(AuditDefinition, None)?;
+    let _diagnostics = registry.register(DiagnosticsDefinition, None)?;
+
+    let publication = PublishedObject::new(ApplicationService::new())
+        .expose(&catalog)?
+        .expose(&audit)?;
+    let object = publication.protocol_object();
+
+    // Model a transport/provider that retained only the protocol object's
+    // opaque strings, then resolved them back through the registry's public API.
+    let catalog_wire_reference = object
+        .interfaces
+        .first()
+        .ok_or_else(|| io::Error::other("catalog interface was not published"))?;
+    let audit_wire_reference = object
+        .interfaces
+        .get(1)
+        .ok_or_else(|| io::Error::other("audit interface was not published"))?;
+    let catalog_reference = registry
+        .resolve(catalog_wire_reference)
+        .ok_or_else(|| io::Error::other("published catalog reference did not resolve"))?;
+    let audit_reference = registry
+        .resolve(audit_wire_reference)
+        .ok_or_else(|| io::Error::other("published audit reference did not resolve"))?;
+    let catalog_observation = registry
+        .observe(&catalog_reference)
+        .ok_or_else(|| io::Error::other("registered catalog descriptor was not observable"))?;
+    let audit_observation = registry
+        .observe(&audit_reference)
+        .ok_or_else(|| io::Error::other("registered audit descriptor was not observable"))?;
+
+    InterfaceObservation {
+        object: object.clone(),
+        descriptors: vec![
+            catalog_observation.descriptor.clone(),
+            audit_observation.descriptor.clone(),
+        ],
+    }
+    .validate()?;
+
+    let published = dispatch_publish(
+        &publication,
+        &catalog_observation.reference,
+        PublishRequest {
+            title: "Public APIs".into(),
+            body: Some("protocol values in, validated values out".into()),
+        },
+    )?;
+    let rejected = dispatch_publish(
+        &publication,
+        &catalog_observation.reference,
+        PublishRequest {
+            title: String::new(),
+            body: None,
+        },
+    )?;
+
+    let catalog_status = dispatch_string(
+        &publication,
+        request(
+            catalog_observation.reference.clone(),
+            Some(Validator::new(CATALOG_VALIDATOR)),
+            "status",
+            vec![],
+        ),
+        "catalog status",
+    )?;
+    let audit_status = dispatch_string(
+        &publication,
+        request(audit_observation.reference.clone(), None, "status", vec![]),
+        "audit status",
+    )?;
+
+    let host_error = match publication.dispatch(request(
+        catalog_observation.reference.clone(),
+        Some(Validator::new(CATALOG_VALIDATOR)),
+        "backend_status",
+        vec![],
+    )) {
+        Ok(_) => {
+            return Err(io::Error::other(
+                "the deliberately unavailable example backend unexpectedly succeeded",
+            )
+            .into());
+        }
+        Err(error) => error,
+    };
+    if host_error.kind() != CallErrorKind::Implementation {
+        return Err(io::Error::other(format!(
+            "unexpected host failure kind: {:?}",
+            host_error.kind()
+        ))
+        .into());
+    }
+    let protocol_error = host_error.protocol_error();
+    let protocol_failure = OperationResult {
+        target: OperationTarget {
+            object: ObjectId(OBJECT_ID.into()),
+            interface: catalog_observation.reference.as_str().into(),
+            operation: "backend_status".into(),
+        },
+        outcome: OperationOutcome::Failed(protocol_error),
+    };
+
+    Ok(DemoReport {
+        published_interfaces: object.interfaces,
+        catalog_descriptor: catalog_observation.descriptor.name,
+        audit_descriptor: audit_observation.descriptor.name,
+        published,
+        rejected,
+        catalog_status,
+        audit_status,
+        host_failure: host_error.kind(),
+        protocol_failure,
+    })
+}
+
+fn dispatch_publish(
+    publication: &PublishedObject<ApplicationService>,
+    catalog: &InterfaceRef,
+    request_value: PublishRequest,
+) -> Result<PublishOutcome, Box<dyn Error>> {
+    let encoded_request = request_value.encode()?;
+    let result = publication.dispatch(request(
+        catalog.clone(),
+        Some(Validator::new(CATALOG_VALIDATOR)),
+        "publish",
+        vec![NamedValue {
+            name: "request".into(),
+            value: encoded_request,
+        }],
+    ))?;
+    let value = result
+        .value
+        .ok_or_else(|| io::Error::other("publish returned no application value"))?;
+    Ok(PublishOutcome::decode(value)?)
+}
+
+fn dispatch_string(
+    publication: &PublishedObject<ApplicationService>,
+    request: CallRequest,
+    context: &str,
+) -> Result<String, Box<dyn Error>> {
+    let result = publication.dispatch(request)?;
+    let value = result
+        .value
+        .ok_or_else(|| io::Error::other(format!("{context} returned no value")))?;
+    Ok(String::decode(value)?)
+}
+
+fn request(
+    interface: InterfaceRef,
+    interface_validator: Option<Validator>,
+    operation: &str,
+    arguments: Vec<NamedValue>,
+) -> CallRequest {
+    CallRequest {
+        object: ObjectId(OBJECT_ID.into()),
+        object_validator: Some(Validator::new(OBJECT_VALIDATOR)),
+        interface: InterfaceTarget {
+            reference: interface,
+            validator: interface_validator,
+        },
+        operation: operation.into(),
+        arguments,
+    }
+}
+
+struct ApplicationService {
+    object_validator: Validator,
+    backend_connection: String,
+}
+
+impl ApplicationService {
+    fn new() -> Self {
+        Self {
+            object_validator: Validator::new(OBJECT_VALIDATOR),
+            backend_connection: "private://article-database".into(),
+        }
+    }
+}
+
+impl WipObject for ApplicationService {
+    fn id(&self) -> ObjectId {
+        ObjectId(OBJECT_ID.into())
+    }
+
+    fn validator(&self) -> Option<&Validator> {
+        Some(&self.object_validator)
+    }
+
+    fn requires_validator(&self) -> bool {
+        true
+    }
+}
+
+impl Catalog for ApplicationService {
+    fn publish(&self, request: PublishRequest) -> wip::OperationResult<PublishOutcome> {
+        if request.title.trim().is_empty() {
+            Ok(PublishOutcome::Rejected("a title is required".into()))
+        } else {
+            Ok(PublishOutcome::Published("article-1".into()))
+        }
+    }
+
+    fn status(&self) -> wip::OperationResult<String> {
+        Ok("catalog-ready".into())
+    }
+
+    fn backend_status(&self) -> wip::OperationResult<String> {
+        if self.backend_connection.starts_with("private://") {
+            Err(wip::HostError::new("backend unavailable"))
+        } else {
+            Ok("backend-ready".into())
+        }
+    }
+}
+
+impl Audit for ApplicationService {
+    fn status(&self) -> wip::OperationResult<String> {
+        Ok("audit-ready".into())
+    }
+}
+
+impl Diagnostics for ApplicationService {
+    fn diagnostics(&self) -> wip::OperationResult<String> {
+        Ok("host-private".into())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use wip_host::CallError;
+    use wip_interface::{CodecError, TypeDeclaration, TypeExpr};
+    use wip_protocol::{ProtocolErrorCategory, Value};
+
+    /// A deliberately inconsistent custom codec used to prove result validation.
+    pub struct InvalidValue;
+
+    impl WipType for InvalidValue {
+        fn type_expr() -> TypeExpr {
+            TypeExpr::String
+        }
+
+        fn collect_declarations(_: &mut Vec<TypeDeclaration>) {}
+
+        fn encode(self) -> Result<Value, CodecError> {
+            Ok(Value::Integer(7))
+        }
+
+        fn decode(_: Value) -> Result<Self, CodecError> {
+            Ok(Self)
+        }
+    }
+
+    /// Test-only interface whose custom codec emits an invalid result.
+    #[wip::interface]
+    pub trait BrokenResult {
+        /// Returns a value that violates its declared protocol type.
+        fn broken_result(&self) -> wip::OperationResult<InvalidValue>;
+    }
+
+    impl BrokenResult for ApplicationService {
+        fn broken_result(&self) -> wip::OperationResult<InvalidValue> {
+            Ok(InvalidValue)
+        }
+    }
+
+    struct Fixture {
+        publication: PublishedObject<ApplicationService>,
+        catalog: InterfaceRef,
+        audit: InterfaceRef,
+        diagnostics: InterfaceRef,
+    }
+
+    fn fixture() -> Fixture {
+        let mut registry = InterfaceRegistry::new();
+        let catalog = registry
+            .register(CatalogDefinition, Some(Validator::new(CATALOG_VALIDATOR)))
+            .unwrap();
+        let audit = registry.register(AuditDefinition, None).unwrap();
+        let diagnostics = registry.register(DiagnosticsDefinition, None).unwrap();
+        let publication = PublishedObject::new(ApplicationService::new())
+            .expose(&catalog)
+            .unwrap()
+            .expose(&audit)
+            .unwrap();
+        Fixture {
+            publication,
+            catalog: catalog.reference().clone(),
+            audit: audit.reference().clone(),
+            diagnostics: diagnostics.reference().clone(),
+        }
+    }
+
+    fn assert_failure(error: CallError, kind: CallErrorKind, category: ProtocolErrorCategory) {
+        assert_eq!(error.kind(), kind);
+        assert_eq!(error.protocol_error().category, category);
+    }
+
+    #[test]
+    fn interface_membership_and_same_name_operations_are_qualified() {
+        let fixture = fixture();
+
+        let catalog = dispatch_string(
+            &fixture.publication,
+            request(
+                fixture.catalog.clone(),
+                Some(Validator::new(CATALOG_VALIDATOR)),
+                "status",
+                vec![],
+            ),
+            "catalog status",
+        )
+        .unwrap();
+        let audit = dispatch_string(
+            &fixture.publication,
+            request(fixture.audit.clone(), None, "status", vec![]),
+            "audit status",
+        )
+        .unwrap();
+        assert_eq!(catalog, "catalog-ready");
+        assert_eq!(audit, "audit-ready");
+
+        let not_exposed = fixture
+            .publication
+            .dispatch(request(fixture.diagnostics, None, "diagnostics", vec![]))
+            .unwrap_err();
+        assert_failure(
+            not_exposed,
+            CallErrorKind::InterfaceMismatch,
+            ProtocolErrorCategory::InterfaceNotFound,
+        );
+    }
+
+    #[test]
+    fn every_host_precondition_and_dispatch_failure_is_typed() {
+        let fixture = fixture();
+
+        let mut wrong_object = request(
+            fixture.catalog.clone(),
+            Some(Validator::new(CATALOG_VALIDATOR)),
+            "status",
+            vec![],
+        );
+        wrong_object.object = ObjectId("other-object".into());
+        assert_failure(
+            fixture.publication.dispatch(wrong_object).unwrap_err(),
+            CallErrorKind::ObjectNotFound,
+            ProtocolErrorCategory::ObjectNotFound,
+        );
+
+        let mut missing_object_validator = request(
+            fixture.catalog.clone(),
+            Some(Validator::new(CATALOG_VALIDATOR)),
+            "status",
+            vec![],
+        );
+        missing_object_validator.object_validator = None;
+        assert_failure(
+            fixture
+                .publication
+                .dispatch(missing_object_validator)
+                .unwrap_err(),
+            CallErrorKind::ValidatorRequired,
+            ProtocolErrorCategory::InvalidRequest,
+        );
+
+        let mut stale_object_validator = request(
+            fixture.catalog.clone(),
+            Some(Validator::new(CATALOG_VALIDATOR)),
+            "status",
+            vec![],
+        );
+        stale_object_validator.object_validator = Some(Validator::new(b"stale-object"));
+        assert_failure(
+            fixture
+                .publication
+                .dispatch(stale_object_validator)
+                .unwrap_err(),
+            CallErrorKind::ValidatorMismatch,
+            ProtocolErrorCategory::InvalidRequest,
+        );
+
+        assert_failure(
+            fixture
+                .publication
+                .dispatch(request(fixture.catalog.clone(), None, "status", vec![]))
+                .unwrap_err(),
+            CallErrorKind::InterfaceValidatorRequired,
+            ProtocolErrorCategory::InvalidRequest,
+        );
+
+        assert_failure(
+            fixture
+                .publication
+                .dispatch(request(
+                    fixture.catalog.clone(),
+                    Some(Validator::new(b"stale-interface")),
+                    "status",
+                    vec![],
+                ))
+                .unwrap_err(),
+            CallErrorKind::InterfaceValidatorMismatch,
+            ProtocolErrorCategory::InvalidRequest,
+        );
+
+        assert_failure(
+            fixture
+                .publication
+                .dispatch(request(
+                    fixture.catalog.clone(),
+                    Some(Validator::new(CATALOG_VALIDATOR)),
+                    "missing",
+                    vec![],
+                ))
+                .unwrap_err(),
+            CallErrorKind::OperationNotFound,
+            ProtocolErrorCategory::OperationNotFound,
+        );
+
+        assert_failure(
+            fixture
+                .publication
+                .dispatch(request(
+                    fixture.catalog.clone(),
+                    Some(Validator::new(CATALOG_VALIDATOR)),
+                    "publish",
+                    vec![NamedValue {
+                        name: "request".into(),
+                        value: Value::String("not a record".into()),
+                    }],
+                ))
+                .unwrap_err(),
+            CallErrorKind::InvalidArguments,
+            ProtocolErrorCategory::InvalidArguments,
+        );
+
+        assert_failure(
+            fixture
+                .publication
+                .dispatch(request(
+                    fixture.catalog,
+                    Some(Validator::new(CATALOG_VALIDATOR)),
+                    "backend_status",
+                    vec![],
+                ))
+                .unwrap_err(),
+            CallErrorKind::Implementation,
+            ProtocolErrorCategory::Internal,
+        );
+    }
+
+    #[test]
+    fn invalid_implementation_result_never_crosses_the_host_boundary() {
+        let mut registry = InterfaceRegistry::new();
+        let broken = registry.register(BrokenResultDefinition, None).unwrap();
+        let publication = PublishedObject::new(ApplicationService::new())
+            .expose(&broken)
+            .unwrap();
+
+        let error = publication
+            .dispatch(request(
+                broken.reference().clone(),
+                None,
+                "broken_result",
+                vec![],
+            ))
+            .unwrap_err();
+        assert_failure(
+            error,
+            CallErrorKind::InvalidResult,
+            ProtocolErrorCategory::Internal,
+        );
+    }
+}

src/main.rs

@@ -1,3 +1,14 @@
-fn main() {
+use std::error::Error;
-    println!("Hello, world!");
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let report = wip_public_api_example::run()?;
+    println!(
+        "published {} interfaces; catalog={}, audit={}; domain={:?}; host={:?}",
+        report.published_interfaces.len(),
+        report.catalog_status,
+        report.audit_status,
+        report.rejected,
+        report.host_failure,
+    );
+    Ok(())
 }

tests/end_to_end.rs

@@ -0,0 +1,27 @@
+use wip_host::CallErrorKind;
+use wip_protocol::{OperationOutcome, ProtocolErrorCategory};
+use wip_public_api_example::{PublishOutcome, run};
+
+#[test]
+fn public_crates_support_the_complete_end_to_end_scenario() {
+    let report = run().unwrap();
+
+    assert_eq!(report.published_interfaces.len(), 2);
+    assert_eq!(report.catalog_descriptor, report.published_interfaces[0]);
+    assert_eq!(report.audit_descriptor, report.published_interfaces[1]);
+    assert_eq!(
+        report.published,
+        PublishOutcome::Published("article-1".into())
+    );
+    assert_eq!(
+        report.rejected,
+        PublishOutcome::Rejected("a title is required".into())
+    );
+    assert_eq!(report.catalog_status, "catalog-ready");
+    assert_eq!(report.audit_status, "audit-ready");
+    assert_eq!(report.host_failure, CallErrorKind::Implementation);
+    assert!(matches!(
+        report.protocol_failure.outcome,
+        OperationOutcome::Failed(error) if error.category == ProtocolErrorCategory::Internal
+    ));
+}