rust: support arrays in target JSON

Some configuration options such as the supported sanitizer list are
arrays. To support using Rust with sanitizers on x86, we must update the
target.json generator to support this case.

The Push trait is removed in favor of the From trait because the Push
trait doesn't work well in the nested case where you are not really
pushing values to a TargetSpec.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Tested-by: Gatlin Newhouse <gatlin.newhouse@gmail.com>
Link: https://lore.kernel.org/r/20240730-target-json-arrays-v1-1-2b376fd0ecf4@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

scripts/generate_rust_target.rs

@@ -20,12 +20,28 @@ enum Value {
     Boolean(bool),
     Number(i32),
     String(String),
+    Array(Vec<Value>),
     Object(Object),
 }
 
 type Object = Vec<(String, Value)>;
 
-/// Minimal "almost JSON" generator (e.g. no `null`s, no arrays, no escaping),
+fn comma_sep<T>(
+    seq: &[T],
+    formatter: &mut Formatter<'_>,
+    f: impl Fn(&mut Formatter<'_>, &T) -> Result,
+) -> Result {
+    if let [ref rest @ .., ref last] = seq[..] {
+        for v in rest {
+            f(formatter, v)?;
+            formatter.write_str(",")?;
+        }
+        f(formatter, last)?;
+    }
+    Ok(())
+}
+
+/// Minimal "almost JSON" generator (e.g. no `null`s, no escaping),
 /// enough for this purpose.
 impl Display for Value {
     fn fmt(&self, formatter: &mut Formatter<'_>) -> Result {
@@ -33,59 +49,67 @@ impl Display for Value {
             Value::Boolean(boolean) => write!(formatter, "{}", boolean),
             Value::Number(number) => write!(formatter, "{}", number),
             Value::String(string) => write!(formatter, "\"{}\"", string),
+            Value::Array(values) => {
+                formatter.write_str("[")?;
+                comma_sep(&values[..], formatter, |formatter, v| v.fmt(formatter))?;
+                formatter.write_str("]")
+            }
             Value::Object(object) => {
                 formatter.write_str("{")?;
-                if let [ref rest @ .., ref last] = object[..] {
-                    for (key, value) in rest {
-                        write!(formatter, "\"{}\": {},", key, value)?;
-                    }
-                    write!(formatter, "\"{}\": {}", last.0, last.1)?;
-                }
+                comma_sep(&object[..], formatter, |formatter, v| {
+                    write!(formatter, "\"{}\": {}", v.0, v.1)
+                })?;
                 formatter.write_str("}")
             }
         }
     }
 }
 
+impl From<bool> for Value {
+    fn from(value: bool) -> Self {
+        Self::Boolean(value)
+    }
+}
+
+impl From<i32> for Value {
+    fn from(value: i32) -> Self {
+        Self::Number(value)
+    }
+}
+
+impl From<String> for Value {
+    fn from(value: String) -> Self {
+        Self::String(value)
+    }
+}
+
+impl From<&str> for Value {
+    fn from(value: &str) -> Self {
+        Self::String(value.to_string())
+    }
+}
+
+impl From<Object> for Value {
+    fn from(object: Object) -> Self {
+        Self::Object(object)
+    }
+}
+
+impl<T: Into<Value>, const N: usize> From<[T; N]> for Value {
+    fn from(i: [T; N]) -> Self {
+        Self::Array(i.into_iter().map(|v| v.into()).collect())
+    }
+}
+
 struct TargetSpec(Object);
 
 impl TargetSpec {
     fn new() -> TargetSpec {
         TargetSpec(Vec::new())
     }
-}
 
-trait Push<T> {
-    fn push(&mut self, key: &str, value: T);
-}
-
-impl Push<bool> for TargetSpec {
-    fn push(&mut self, key: &str, value: bool) {
-        self.0.push((key.to_string(), Value::Boolean(value)));
-    }
-}
-
-impl Push<i32> for TargetSpec {
-    fn push(&mut self, key: &str, value: i32) {
-        self.0.push((key.to_string(), Value::Number(value)));
-    }
-}
-
-impl Push<String> for TargetSpec {
-    fn push(&mut self, key: &str, value: String) {
-        self.0.push((key.to_string(), Value::String(value)));
-    }
-}
-
-impl Push<&str> for TargetSpec {
-    fn push(&mut self, key: &str, value: &str) {
-        self.push(key, value.to_string());
-    }
-}
-
-impl Push<Object> for TargetSpec {
-    fn push(&mut self, key: &str, value: Object) {
-        self.0.push((key.to_string(), Value::Object(value)));
+    fn push(&mut self, key: &str, value: impl Into<Value>) {
+        self.0.push((key.to_string(), value.into()));
     }
 }