[3/n] allow JSON schemas relative to the out dir

Cargo.toml

@@ -3,6 +3,7 @@ members = [
 	"cargo-progenitor",
 	"example-build",
 	"example-macro",
+	"example-out-dir",
 	"example-wasm",
 	"progenitor",
 	"progenitor-client",

example-out-dir/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "example-out-dir"
+version = "0.0.1"
+edition.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+chrono = { version = "0.4", features = ["serde"] }
+progenitor = { path = "../progenitor" }
+reqwest = { version = "0.13.1", features = ["json", "query", "stream"] }
+serde = { version = "1.0", features = ["derive"] }
+uuid = { version = "1.20", features = ["serde", "v4"] }

example-out-dir/build.rs

@@ -0,0 +1,17 @@
+// Copyright 2026 Oxide Computer Company
+
+use std::{env, fs, path::Path};
+
+fn main() {
+    // Example build script showing integration with OUT_DIR.
+    //
+    // This build script copies a sample OpenAPI document to OUT_DIR. A more
+    // complex build script might, for example, extract the OpenAPI document
+    // from a non-file source, writing it out to OUT_DIR.
+    let src = "../sample_openapi/keeper.json";
+    println!("cargo:rerun-if-changed={}", src);
+
+    let out_dir = env::var("OUT_DIR").unwrap();
+    let dest = Path::new(&out_dir).join("keeper.json");
+    fs::copy(src, dest).unwrap();
+}

example-out-dir/release.toml

@@ -0,0 +1 @@
+release = false

example-out-dir/src/main.rs

@@ -0,0 +1,21 @@
+// Copyright 2026 Oxide Computer Company
+
+//! Test that `generate_api!` works with `relative_to = OutDir`, where a build
+//! script copies the spec into `OUT_DIR`.
+
+use progenitor::generate_api;
+
+generate_api!(
+    spec = { path = "keeper.json", relative_to = OutDir },
+);
+
+fn main() {
+    let client = Client::new("https://example.com");
+    std::mem::drop(client.enrol(
+        "auth-token",
+        &types::EnrolBody {
+            host: "".to_string(),
+            key: "".to_string(),
+        },
+    ));
+}

progenitor-macro/Cargo.toml

@@ -20,5 +20,5 @@ schemars = "0.8.22"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 serde_yaml = "0.9"
-serde_tokenstream = "0.2.0"
+serde_tokenstream = "0.2.3"
 syn = { version = "2.0", features = ["full", "extra-traits"] }

progenitor-macro/src/lib.rs

@@ -1,14 +1,10 @@
-// Copyright 2022 Oxide Computer Company
+// Copyright 2026 Oxide Computer Company
 
 //! Macros for the progenitor OpenAPI client generator.
 
 #![deny(missing_docs)]
 
-use std::{
-    collections::HashMap,
-    fs::File,
-    path::{Path, PathBuf},
-};
+use std::{collections::HashMap, fs::File, path::PathBuf};
 
 use openapiv3::OpenAPI;
 use proc_macro::TokenStream;
@@ -24,6 +20,58 @@ use token_utils::TypeAndImpls;
 
 mod token_utils;
 
+/// Where to resolve the spec path relative to.
+#[derive(Debug, Clone, Copy, Deserialize)]
+enum RelativeTo {
+    /// Resolve relative to CARGO_MANIFEST_DIR (the default).
+    ManifestDir,
+    /// Resolve relative to OUT_DIR.
+    OutDir,
+}
+
+/// Specification of where to find the OpenAPI document.
+#[derive(Debug)]
+struct SpecSource {
+    /// The path to the spec file.
+    path: LitStr,
+    /// Where to resolve the path relative to.
+    relative_to: RelativeTo,
+}
+
+impl syn::parse::Parse for SpecSource {
+    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
+        /// Helper struct for deserializing the struct form of SpecSource.
+        #[derive(Deserialize)]
+        struct SpecSourceStruct {
+            path: ParseWrapper<LitStr>,
+            relative_to: RelativeTo,
+        }
+
+        let lookahead = input.lookahead1();
+        if lookahead.peek(LitStr) {
+            // spec = "path/to/spec.json"
+            let path: LitStr = input.parse()?;
+            Ok(SpecSource {
+                path,
+                relative_to: RelativeTo::ManifestDir,
+            })
+        } else if lookahead.peek(syn::token::Brace) {
+            // spec = { path = "...", relative_to = ... }
+            let content;
+            let brace_token = syn::braced!(content in input);
+            let stream: proc_macro2::TokenStream = content.parse()?;
+            let helper: SpecSourceStruct =
+                serde_tokenstream::from_tokenstream_spanned(&brace_token.span, &stream)?;
+            Ok(SpecSource {
+                path: helper.path.into_inner(),
+                relative_to: helper.relative_to,
+            })
+        } else {
+            Err(lookahead.error())
+        }
+    }
+}
+
 /// Generates a client from the given OpenAPI document
 ///
 /// `generate_api!` can be invoked in two ways. The simple form, takes a path
@@ -35,7 +83,10 @@ mod token_utils;
 /// The more complex form accepts the following key-value pairs in any order:
 /// ```ignore
 /// generate_api!(
+///     // spec can be a simple path string:
 ///     spec = "path/to/spec.json",
+///     // Or a struct with path and relative_to:
+///     spec = { path = "path/to/spec.json", relative_to = OutDir },
 ///     [ interface = ( Positional | Builder ), ]
 ///     [ tags = ( Merged | Separate ), ]
 ///     [ pre_hook = closure::or::path::to::function, ]
@@ -56,7 +107,13 @@ mod token_utils;
 /// ```
 ///
 /// The `spec` key is required; it is the OpenAPI document (JSON or YAML) from
-/// which the client is derived.
+/// which the client is derived. It can be specified as a simple string path, or
+/// as a struct with `path` and `relative_to` fields. The `relative_to`
+/// field controls where the path is resolved from:
+///
+/// - `ManifestDir`: relative to `CARGO_MANIFEST_DIR`. This is the default when
+///   the spec is provided as a string path.
+/// - `OutDir`: relative to `OUT_DIR` (useful for build script outputs).
 ///
 /// The optional `interface` lets you specify either a `Positional` argument or
 /// `Builder` argument style; `Positional` is the default.
@@ -129,7 +186,7 @@ pub fn generate_api(item: TokenStream) -> TokenStream {
 
 #[derive(Deserialize)]
 struct MacroSettings {
-    spec: ParseWrapper<LitStr>,
+    spec: ParseWrapper<SpecSource>,
     #[serde(default)]
     interface: InterfaceStyle,
     #[serde(default)]
@@ -273,8 +330,12 @@ fn open_file(path: PathBuf, span: proc_macro2::Span) -> Result<File, syn::Error>
 }
 
 fn do_generate_api(item: TokenStream) -> Result<TokenStream, syn::Error> {
-    let (spec, settings) = if let Ok(spec) = syn::parse::<LitStr>(item.clone()) {
-        (spec, GenerationSettings::default())
+    let (spec_source, settings) = if let Ok(spec) = syn::parse::<LitStr>(item.clone()) {
+        let spec_source = SpecSource {
+            path: spec,
+            relative_to: RelativeTo::ManifestDir,
+        };
+        (spec_source, GenerationSettings::default())
     } else {
         let MacroSettings {
             spec,
@@ -295,6 +356,8 @@ fn do_generate_api(item: TokenStream) -> Result<TokenStream, syn::Error> {
             timeout,
         } = serde_tokenstream::from_tokenstream(&item.into())?;
 
+        let spec = spec.into_inner();
+
         let mut settings = GenerationSettings::default();
         settings.with_interface(interface);
         settings.with_tag(tags);
@@ -336,24 +399,38 @@ fn do_generate_api(item: TokenStream) -> Result<TokenStream, syn::Error> {
         if let Some(timeout) = timeout {
             settings.with_timeout(timeout);
         }
-        (spec.into_inner(), settings)
+        (spec, settings)
     };
 
-    let dir = std::env::var("CARGO_MANIFEST_DIR").map_or_else(
-        |_| std::env::current_dir().unwrap(),
-        |s| Path::new(&s).to_path_buf(),
-    );
+    let spec_path = spec_source.path;
+    let base_dir = match spec_source.relative_to {
+        RelativeTo::ManifestDir => std::env::var("CARGO_MANIFEST_DIR")
+            .map_or_else(|_| std::env::current_dir().unwrap(), PathBuf::from),
+        RelativeTo::OutDir => {
+            let out_dir = std::env::var("OUT_DIR").map_err(|_| {
+                syn::Error::new(
+                    spec_path.span(),
+                    "relative_to = OutDir requires OUT_DIR to be set \
+                     (are you using this from a build script?)",
+                )
+            })?;
+            PathBuf::from(out_dir)
+        }
+    };
 
-    let path = dir.join(spec.value());
+    let path = base_dir.join(spec_path.value());
     let path_str = path.to_string_lossy();
 
-    let mut f = open_file(path.clone(), spec.span())?;
+    let mut f = open_file(path.clone(), spec_path.span())?;
     let oapi: OpenAPI = match serde_json::from_reader(f) {
         Ok(json_value) => json_value,
         _ => {
-            f = open_file(path.clone(), spec.span())?;
+            f = open_file(path.clone(), spec_path.span())?;
             serde_yaml::from_reader(f).map_err(|e| {
-                syn::Error::new(spec.span(), format!("failed to parse {}: {}", path_str, e))
+                syn::Error::new(
+                    spec_path.span(),
+                    format!("failed to parse {}: {}", path_str, e),
+                )
             })?
         }
     };
@@ -362,8 +439,8 @@ fn do_generate_api(item: TokenStream) -> Result<TokenStream, syn::Error> {
 
     let code = builder.generate_tokens(&oapi).map_err(|e| {
         syn::Error::new(
-            spec.span(),
-            format!("generation error for {}: {}", spec.value(), e),
+            spec_path.span(),
+            format!("generation error for {}: {}", spec_path.value(), e),
         )
     })?;
 

progenitor/Cargo.toml

@@ -30,5 +30,5 @@ reqwest = { workspace = true }
 schemars = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
-tokio = { workspace = true }
+tokio = { workspace = true, features = ["macros"] }
 uuid = { workspace = true }