Add --print target-spec-json-schema

This schema is helpful for people writing custom target spec JSON. It
can provide autocomplete in the editor, and also serves as documentation
when there are documentation comments on the structs, as `schemars` will
put them in the schema.

Author: Noratrieb

Cargo.lock

@@ -1133,6 +1133,12 @@ version = "1.0.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8975ffdaa0ef3661bfe02dbdcc06c9f829dfafe6a3c474de366a8d5e44276921"
 
+[[package]]
+name = "dyn-clone"
+version = "1.0.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1c7a8fb8a9fbf66c1f703fe16184d10ca0ee9d23be5b4436400408ba54a95005"
+
 [[package]]
 name = "either"
 version = "1.15.0"
@@ -3077,6 +3083,26 @@ dependencies = [
  "thiserror 2.0.12",
 ]
 
+[[package]]
+name = "ref-cast"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4a0ae411dbe946a674d89546582cea4ba2bb8defac896622d6496f14c23ba5cf"
+dependencies = [
+ "ref-cast-impl",
+]
+
+[[package]]
+name = "ref-cast-impl"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1165225c21bff1f3bbce98f5a1f889949bc902d3575308cc7b0de30b4f6d27c7"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.104",
+]
+
 [[package]]
 name = "regex"
 version = "1.11.1"
@@ -4563,6 +4589,7 @@ dependencies = [
  "rustc_macros",
  "rustc_serialize",
  "rustc_span",
+ "schemars",
  "serde",
  "serde_derive",
  "serde_json",
@@ -4878,6 +4905,31 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "schemars"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "82d20c4491bc164fa2f6c5d44565947a52ad80b9505d8e36f8d54c27c739fcd0"
+dependencies = [
+ "dyn-clone",
+ "ref-cast",
+ "schemars_derive",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "schemars_derive"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "33d020396d1d138dc19f1165df7545479dcd58d93810dc5d646a16e55abefa80"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "serde_derive_internals",
+ "syn 2.0.104",
+]
+
 [[package]]
 name = "scoped-tls"
 version = "1.0.1"
@@ -4946,6 +4998,17 @@ dependencies = [
  "syn 2.0.104",
 ]
 
+[[package]]
+name = "serde_derive_internals"
+version = "0.29.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "18d26a20a969b9e3fdf2fc2d9f21eda6c40e2de84c9408bb5d3b05d499aae711"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.104",
+]
+
 [[package]]
 name = "serde_json"
 version = "1.0.141"

compiler/rustc_codegen_ssa/src/back/command.rs

@@ -109,7 +109,7 @@ impl Command {
             }
             Program::Lld(ref p, flavor) => {
                 let mut c = process::Command::new(p);
-                c.arg("-flavor").arg(flavor.as_str());
+                c.arg("-flavor").arg(flavor.desc());
                 c
             }
         };

compiler/rustc_driver_impl/src/lib.rs

@@ -667,6 +667,10 @@ fn print_crate_info(
             TargetSpecJson => {
                 println_info!("{}", serde_json::to_string_pretty(&sess.target.to_json()).unwrap());
             }
+            TargetSpecJsonSchema => {
+                let schema = rustc_target::spec::json_schema();
+                println_info!("{}", serde_json::to_string_pretty(&schema).unwrap());
+            }
             AllTargetSpecsJson => {
                 let mut targets = BTreeMap::new();
                 for name in rustc_target::spec::TARGETS {

compiler/rustc_session/src/config.rs

@@ -69,6 +69,7 @@ pub const PRINT_KINDS: &[(&str, PrintKind)] = &[
     ("target-libdir", PrintKind::TargetLibdir),
     ("target-list", PrintKind::TargetList),
     ("target-spec-json", PrintKind::TargetSpecJson),
+    ("target-spec-json-schema", PrintKind::TargetSpecJsonSchema),
     ("tls-models", PrintKind::TlsModels),
     // tidy-alphabetical-end
 ];
@@ -1052,6 +1053,7 @@ pub enum PrintKind {
     TargetLibdir,
     TargetList,
     TargetSpecJson,
+    TargetSpecJsonSchema,
     TlsModels,
     // tidy-alphabetical-end
 }
@@ -2314,7 +2316,8 @@ fn is_print_request_stable(print_kind: PrintKind) -> bool {
         | PrintKind::CheckCfg
         | PrintKind::CrateRootLintLevels
         | PrintKind::SupportedCrateTypes
-        | PrintKind::TargetSpecJson => false,
+        | PrintKind::TargetSpecJson
+        | PrintKind::TargetSpecJsonSchema => false,
         _ => true,
     }
 }

compiler/rustc_target/Cargo.toml

@@ -12,6 +12,7 @@ rustc_fs_util = { path = "../rustc_fs_util" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
+schemars = "1.0.4"
 serde = "1.0.219"
 serde_derive = "1.0.219"
 serde_json = "1.0.59"

compiler/rustc_target/src/lib.rs

@@ -86,9 +86,11 @@ macro_rules! target_spec_enum {
     ) => {
         $( #[$attr] )*
         #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, PartialOrd, Ord)]
+        #[derive(schemars::JsonSchema)]
         pub enum $name {
             $(
                 $( #[$variant_attr] )*
+                #[serde(rename = $string)] // for JSON schema generation only
                 $variant,
             )*
         }

compiler/rustc_target/src/spec/json.rs

@@ -413,12 +413,12 @@ impl ToJson for Target {
     }
 }
 
-#[derive(serde_derive::Deserialize)]
+#[derive(serde_derive::Deserialize, schemars::JsonSchema)]
 struct LinkSelfContainedComponentsWrapper {
     components: Vec<LinkSelfContainedComponents>,
 }
 
-#[derive(serde_derive::Deserialize)]
+#[derive(serde_derive::Deserialize, schemars::JsonSchema)]
 #[serde(untagged)]
 enum TargetFamiliesJson {
     Array(StaticCow<[StaticCow<str>]>),
@@ -434,6 +434,18 @@ impl FromStr for EndianWrapper {
     }
 }
 crate::json::serde_deserialize_from_str!(EndianWrapper);
+impl schemars::JsonSchema for EndianWrapper {
+    fn schema_name() -> std::borrow::Cow<'static, str> {
+        "Endian".into()
+    }
+    fn json_schema(_: &mut schemars::SchemaGenerator) -> schemars::Schema {
+        schemars::json_schema! ({
+            "type": "string",
+            "enum": ["big", "little"]
+        })
+        .into()
+    }
+}
 
 /// `ExternAbi` is in `rustc_abi`, which doesn't have access to the macro and serde.
 struct ExternAbiWrapper(rustc_abi::ExternAbi);
@@ -446,16 +458,30 @@ impl FromStr for ExternAbiWrapper {
     }
 }
 crate::json::serde_deserialize_from_str!(ExternAbiWrapper);
+impl schemars::JsonSchema for ExternAbiWrapper {
+    fn schema_name() -> std::borrow::Cow<'static, str> {
+        "ExternAbi".into()
+    }
+    fn json_schema(_: &mut schemars::SchemaGenerator) -> schemars::Schema {
+        let all =
+            rustc_abi::ExternAbi::ALL_VARIANTS.iter().map(|abi| abi.as_str()).collect::<Vec<_>>();
+        schemars::json_schema! ({
+            "type": "string",
+            "enum": all,
+        })
+        .into()
+    }
+}
 
-#[derive(serde_derive::Deserialize)]
+#[derive(serde_derive::Deserialize, schemars::JsonSchema)]
 struct TargetSpecJsonMetadata {
     description: Option<StaticCow<str>>,
     tier: Option<u64>,
     host_tools: Option<bool>,
     std: Option<bool>,
 }
 
-#[derive(serde_derive::Deserialize)]
+#[derive(serde_derive::Deserialize, schemars::JsonSchema)]
 #[serde(rename_all = "kebab-case")]
 // Ensure that all unexpected fields get turned into errors.
 // This helps users stay up to date when the schema changes instead of silently
@@ -598,3 +624,7 @@ struct TargetSpecJson {
     supports_xray: Option<bool>,
     entry_abi: Option<ExternAbiWrapper>,
 }
+
+pub fn json_schema() -> schemars::Schema {
+    schemars::schema_for!(TargetSpecJson)
+}

compiler/rustc_target/src/spec/mod.rs

@@ -69,6 +69,7 @@ mod json;
 pub use abi_map::{AbiMap, AbiMapping};
 pub use base::apple;
 pub use base::avr::ef_avr_arch;
+pub use json::json_schema;
 
 /// Linker is called through a C/C++ compiler.
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
@@ -522,6 +523,20 @@ linker_flavor_cli_impls! {
 }
 
 crate::json::serde_deserialize_from_str!(LinkerFlavorCli);
+impl schemars::JsonSchema for LinkerFlavorCli {
+    fn schema_name() -> std::borrow::Cow<'static, str> {
+        "LinkerFlavor".into()
+    }
+    fn json_schema(_: &mut schemars::SchemaGenerator) -> schemars::Schema {
+        let all: Vec<&'static str> =
+            Self::all().iter().map(|flavor| flavor.desc()).collect::<Vec<_>>();
+        schemars::json_schema! ({
+            "type": "string",
+            "enum": all
+        })
+        .into()
+    }
+}
 
 impl ToJson for LinkerFlavorCli {
     fn to_json(&self) -> Json {
@@ -575,6 +590,18 @@ impl FromStr for LinkSelfContainedDefault {
 }
 
 crate::json::serde_deserialize_from_str!(LinkSelfContainedDefault);
+impl schemars::JsonSchema for LinkSelfContainedDefault {
+    fn schema_name() -> std::borrow::Cow<'static, str> {
+        "LinkSelfContainedDefault".into()
+    }
+    fn json_schema(_: &mut schemars::SchemaGenerator) -> schemars::Schema {
+        schemars::json_schema! ({
+            "type": "string",
+            "enum": ["false", "true", "wasm", "musl", "mingw"]
+        })
+        .into()
+    }
+}
 
 impl ToJson for LinkSelfContainedDefault {
     fn to_json(&self) -> Json {
@@ -707,6 +734,20 @@ impl FromStr for LinkSelfContainedComponents {
 }
 
 crate::json::serde_deserialize_from_str!(LinkSelfContainedComponents);
+impl schemars::JsonSchema for LinkSelfContainedComponents {
+    fn schema_name() -> std::borrow::Cow<'static, str> {
+        "LinkSelfContainedComponents".into()
+    }
+    fn json_schema(_: &mut schemars::SchemaGenerator) -> schemars::Schema {
+        let all =
+            Self::all_components().iter().map(|component| component.as_str()).collect::<Vec<_>>();
+        schemars::json_schema! ({
+            "type": "string",
+            "enum": all,
+        })
+        .into()
+    }
+}
 
 impl ToJson for LinkSelfContainedComponents {
     fn to_json(&self) -> Json {
@@ -839,7 +880,6 @@ crate::target_spec_enum! {
     parse_error_type = "symbol visibility";
 }
 
-
 #[derive(Clone, Debug, PartialEq, Hash)]
 pub enum SmallDataThresholdSupport {
     None,
@@ -867,6 +907,17 @@ impl FromStr for SmallDataThresholdSupport {
 }
 
 crate::json::serde_deserialize_from_str!(SmallDataThresholdSupport);
+impl schemars::JsonSchema for SmallDataThresholdSupport {
+    fn schema_name() -> std::borrow::Cow<'static, str> {
+        "SmallDataThresholdSupport".into()
+    }
+    fn json_schema(_: &mut schemars::SchemaGenerator) -> schemars::Schema {
+        schemars::json_schema! ({
+            "type": "string",
+        })
+        .into()
+    }
+}
 
 impl ToJson for SmallDataThresholdSupport {
     fn to_json(&self) -> Value {
@@ -1065,7 +1116,7 @@ crate::target_spec_enum! {
     parse_error_type = "split debuginfo";
 }
 
-#[derive(Clone, Debug, PartialEq, Eq, serde_derive::Deserialize)]
+#[derive(Clone, Debug, PartialEq, Eq, serde_derive::Deserialize, schemars::JsonSchema)]
 #[serde(tag = "kind")]
 #[serde(rename_all = "kebab-case")]
 pub enum StackProbeType {
@@ -1226,6 +1277,19 @@ impl FromStr for SanitizerSet {
 }
 
 crate::json::serde_deserialize_from_str!(SanitizerSet);
+impl schemars::JsonSchema for SanitizerSet {
+    fn schema_name() -> std::borrow::Cow<'static, str> {
+        "SanitizerSet".into()
+    }
+    fn json_schema(_: &mut schemars::SchemaGenerator) -> schemars::Schema {
+        let all = Self::all().iter().map(|sanitizer| sanitizer.as_str()).collect::<Vec<_>>();
+        schemars::json_schema! ({
+            "type": "string",
+            "enum": all,
+        })
+        .into()
+    }
+}
 
 impl ToJson for SanitizerSet {
     fn to_json(&self) -> Json {
@@ -1317,7 +1381,6 @@ impl BinaryFormat {
     }
 }
 
-
 impl ToJson for Align {
     fn to_json(&self) -> Json {
         self.bits().to_json()