Add json schema (#2193)

* feat: add json schema generation for CasConfig via schemars

---------

Co-authored-by: pegasust <pegasucksgg@gmail.com>

Author: palfrey

.github/workflows/native-cargo.yaml

@@ -50,3 +50,6 @@ jobs:
 
       - name: Test on ${{ runner.os }}
         run: cargo test --all --profile=smol
+
+      - name: Check schema export
+        run: cargo run --bin build-schema --features dev-schema --package nativelink-config

.gitignore

@@ -24,3 +24,4 @@ darwin.bazelrc
 nativelink.bazelrc
 *.log
 buck-out/
+nativelink_config.schema.json

Cargo.lock

@@ -14,6 +14,10 @@ humantime = { version = "2.3.0", default-features = false }
 rand = { version = "0.9.0", default-features = false, features = [
   "thread_rng",
 ] }
+schemars = { version = "1.2.1", default-features = false, features = [
+  "derive",
+  "std",
+], optional = true }
 serde = { version = "1.0.219", default-features = false, features = ["derive"] }
 serde_json = { version = "1.0.140", default-features = false, features = [
   "std",
@@ -31,3 +35,11 @@ pretty_assertions = { version = "1.4.1", features = [
 tracing-test = { version = "0.2.5", default-features = false, features = [
   "no-env-filter",
 ] }
+
+[features]
+dev-schema = ["schemars"]
+
+[[bin]]
+name = "build-schema"
+path = "src/bin/build_schema.rs"
+required-features = ["dev-schema"]

nativelink-config/Cargo.toml

@@ -0,0 +1,24 @@
+//! ```sh
+//! cargo run --bin build-schema --features dev-schema --package nativelink-config
+//! ```
+
+#[cfg(feature = "dev-schema")]
+fn main() {
+    use std::fs::File;
+
+    use nativelink_config::cas_server::CasConfig;
+    use schemars::schema_for;
+    use serde_json::to_writer_pretty;
+    const FILE: &str = "nativelink_config.schema.json";
+
+    let schema = schema_for!(CasConfig);
+    to_writer_pretty(File::create(FILE).expect("to create file"), &schema)
+        .expect("to export schema");
+
+    println!("Wrote schema to {FILE}");
+}
+
+#[cfg(not(feature = "dev-schema"))]
+fn main() {
+    eprintln!("Enable with --features dev-schema");
+}