Auto merge of #13290 - poliorcetics:multiple-targets, r=Veykril

Support multiple targets for checkOnSave (in conjunction with cargo 1.64.0+)

This PR adds support for the ability to pass multiple `--target` flags when using
`cargo` 1.64.0+.

## Questions

I needed to change the type of two configurations options, but I did not plurialize the names to
avoid too much churn, should I ?

## Zulip thread

https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer/topic/Issue.2013282.20.28supporting.20multiple.20targets.20with.201.2E64.2B.29

## Example

To see it working, on a macOS machine:

```sh
$ cd /tmp
$ cargo new cargo-multiple-targets-support-ra-test
$ cd !$
$ mkdir .cargo
$ echo '
[build]
target = [
    "aarch64-apple-darwin",
    "x86_64-apple-darwin",
]
' > .cargo/config.toml
$ echo '
fn main() {
    #[cfg(all(target_arch = "aarch64", target_os = "macos"))]
    {
        let a = std::fs::read_to_string("/tmp/test-read");
    }

    #[cfg(all(target_arch = "x86_64", target_os = "macos"))]
    {
        let a = std::fs::read_to_string("/tmp/test-read");
    }

    #[cfg(all(target_arch = "x86_64", target_os = "windows"))]
    {
        let a = std::fs::read_to_string("/tmp/test-read");
    }
}
' > src/main.rs
# launch your favorite editor with the version of RA from this PR
#
# You should see warnings under the first two `let a = ...` but not the third
```

## Screen

![Two panes of a terminal emulator, on the left pane is the main.rs file described above, with warnings for the first two let a = declaration, on the right pane is a display of the .cargo/config.toml, an ls of the current files in the directory and a call to cargo build to show the same warnings as in the editor on the left pane](https://user-images.githubusercontent.com/7951708/192122707-7a00606a-e581-4534-b9d5-b81c92694e8e.png)

Helps with #13282

crates/rust-analyzer/src/config.rs

@@ -118,9 +118,11 @@ config_data! {
         /// This option does not take effect until rust-analyzer is restarted.
         cargo_sysroot: Option<String>    = "\"discover\"",
         /// Compilation target override (target triple).
+        // FIXME(@poliorcetics): move to multiple targets here too, but this will need more work
+        // than `checkOnSave_target`
         cargo_target: Option<String>     = "null",
         /// Unsets `#[cfg(test)]` for the specified crates.
-        cargo_unsetTest: Vec<String>   = "[\"core\"]",
+        cargo_unsetTest: Vec<String>     = "[\"core\"]",
 
         /// Check all targets and tests (`--all-targets`).
         checkOnSave_allTargets: bool                     = "true",
@@ -174,9 +176,13 @@ config_data! {
         /// ```
         /// .
         checkOnSave_overrideCommand: Option<Vec<String>> = "null",
-        /// Check for a specific target. Defaults to
-        /// `#rust-analyzer.cargo.target#`.
-        checkOnSave_target: Option<String>               = "null",
+        /// Check for specific targets. Defaults to `#rust-analyzer.cargo.target#` if empty.
+        ///
+        /// Can be a single target, e.g. `"x86_64-unknown-linux-gnu"` or a list of targets, e.g.
+        /// `["aarch64-apple-darwin", "x86_64-apple-darwin"]`.
+        ///
+        /// Aliased as `"checkOnSave.targets"`.
+        checkOnSave_target | checkOnSave_targets: CheckOnSaveTargets           = "[]",
 
         /// Toggles the additional completions that automatically add imports when completed.
         /// Note that your client must specify the `additionalTextEdits` LSP client capability to truly have this feature enabled.
@@ -1147,11 +1153,10 @@ impl Config {
             }
             Some(_) | None => FlycheckConfig::CargoCommand {
                 command: self.data.checkOnSave_command.clone(),
-                target_triple: self
-                    .data
-                    .checkOnSave_target
-                    .clone()
-                    .or_else(|| self.data.cargo_target.clone()),
+                target_triples: match &self.data.checkOnSave_target.0[..] {
+                    [] => self.data.cargo_target.clone().into_iter().collect(),
+                    targets => targets.into(),
+                },
                 all_targets: self.data.checkOnSave_allTargets,
                 no_default_features: self
                     .data
@@ -1657,6 +1662,9 @@ enum InvocationStrategy {
     PerWorkspace,
 }
 
+#[derive(Deserialize, Debug, Clone)]
+struct CheckOnSaveTargets(#[serde(deserialize_with = "single_or_array")] Vec<String>);
+
 #[derive(Deserialize, Debug, Clone)]
 #[serde(rename_all = "snake_case")]
 enum InvocationLocation {
@@ -2118,6 +2126,17 @@ fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json
                 "The command will be executed in the project root."
             ],
         },
+        "CheckOnSaveTargets" => set! {
+            "anyOf": [
+                {
+                    "type": "string",
+                },
+                {
+                    "type": "array",
+                    "items": { "type": "string" }
+                },
+            ],
+        },
         _ => panic!("missing entry for {}: {}", ty, default),
     }