Make RustTarget parsing more permissive

bindgen/features.rs

@@ -44,7 +44,7 @@ macro_rules! define_rust_targets {
         }
 
         impl RustTarget {
-            fn minor(self) -> Option<u64> {
+            const fn minor(self) -> Option<u64> {
                 match self {
                     $( Self::$variant => Some($minor),)*
                     Self::Nightly => None
@@ -136,15 +136,15 @@ define_rust_targets! {
     Stable_1_0(0) => {},
 }
 
-/// Latest stable release of Rust
+/// Latest stable release of Rust that is supported by bindgen
 pub const LATEST_STABLE_RUST: RustTarget = {
     // FIXME: replace all this code by
     // ```
     // RustTarget::stable_releases()
     //     .into_iter()
     //     .max_by_key(|(_, m)| m)
     //     .map(|(t, _)| t)
-    //     .unwrap_or(RustTarget::Nightly)
+    //     .unwrap()
     // ```
     // once those operations can be used in constants.
     let targets = RustTarget::stable_releases();
@@ -170,6 +170,42 @@ pub const LATEST_STABLE_RUST: RustTarget = {
     }
 };
 
+/// Earliest stable release of Rust that is supported by bindgen
+pub const EARLIEST_STABLE_RUST: RustTarget = {
+    // FIXME: replace all this code by
+    // ```
+    // RustTarget::stable_releases()
+    //     .into_iter()
+    //     .min_by_key(|(_, m)| m)
+    //     .map(|(t, _)| t)
+    //     .unwrap_or(LATEST_STABLE_RUST)
+    // ```
+    // once those operations can be used in constants.
+    let targets = RustTarget::stable_releases();
+
+    let mut i = 0;
+    let mut earliest_target = None;
+    let Some(mut earliest_minor) = LATEST_STABLE_RUST.minor() else {
+        unreachable!()
+    };
+
+    while i < targets.len() {
+        let (target, minor) = targets[i];
+
+        if earliest_minor > minor {
+            earliest_minor = minor;
+            earliest_target = Some(target);
+        }
+
+        i += 1;
+    }
+
+    match earliest_target {
+        Some(target) => target,
+        None => unreachable!(),
+    }
+};
+
 impl Default for RustTarget {
     fn default() -> Self {
         LATEST_STABLE_RUST
@@ -193,28 +229,62 @@ impl Ord for RustTarget {
     }
 }
 
+fn invalid_input<T>(input: &str, msg: impl std::fmt::Display) -> io::Result<T> {
+    Err(io::Error::new(
+        io::ErrorKind::InvalidInput,
+        format!("\"{input}\" is not a valid Rust target, {msg}"),
+    ))
+}
+
 impl FromStr for RustTarget {
     type Err = io::Error;
 
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        if s == "nightly" {
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        if input == "nightly" {
             return Ok(Self::Nightly);
         }
 
-        if let Some(("1", str_minor)) = s.split_once('.') {
-            if let Ok(minor) = str_minor.parse::<u64>() {
-                for (target, target_minor) in Self::stable_releases() {
-                    if minor == target_minor {
-                        return Ok(target);
-                    }
-                }
-            }
+        let Some((major_str, tail)) = input.split_once('.') else {
+            return invalid_input(input, "accepted values are of the form \"1.71\", \"1.71.1\" or \"nightly\"." );
+        };
+
+        if major_str != "1" {
+            return invalid_input(
+                input,
+                "The largest major version of Rust released is \"1\"",
+            );
         }
 
-        Err(io::Error::new(
-            io::ErrorKind::InvalidInput,
-            "Got an invalid Rust target. Accepted values are of the form \"1.71\" or \"nightly\"."
-        ))
+        // We ignore the patch version number as they only include backwards compatible bug fixes.
+        let (minor, _patch) = match tail.split_once('.') {
+            Some((minor_str, patch_str)) => {
+                let Ok(minor) = minor_str.parse::<u64>() else {
+                    return invalid_input(input, "the minor version number must be an unsigned 64-bit integer");
+                };
+                let Ok(patch) = patch_str.parse::<u64>() else {
+                    return invalid_input(input, "the patch version number must be an unsigned 64-bit integer");
+                };
+                (minor, patch)
+            }
+            None => {
+                let Ok(minor) = tail.parse::<u64>() else {
+                    return invalid_input(input, "the minor version number must be an unsigned 64-bit integer");
+                };
+                (minor, 0)
+            }
+        };
+
+        let Some(target) = Self::stable_releases()
+            .iter()
+            .filter(|(_, target_minor)| minor >= *target_minor)
+            .max_by_key(|(_, target_minor)| target_minor)
+            .map(|(target, _)| target)
+            .cloned()
+        else {
+            return invalid_input(input, format!("the earliest Rust target supported by bindgen is {EARLIEST_STABLE_RUST}"));
+        };
+
+        Ok(target)
     }
 }
 
@@ -282,19 +352,37 @@ mod test {
     }
 
     fn test_target(target_str: &str, target: RustTarget) {
-        let target_string = target.to_string();
-        assert_eq!(target_str, target_string);
-        assert_eq!(target, RustTarget::from_str(target_str).unwrap());
+        assert_eq!(
+            target,
+            target_str.parse::<RustTarget>().unwrap(),
+            "{target_str}"
+        );
+    }
+
+    fn test_invalid_target(target_str: &str) {
+        assert!(target_str.parse::<RustTarget>().is_err(), "{}", target_str);
     }
 
     #[test]
-    fn str_to_target() {
-        test_target("1.0", RustTarget::Stable_1_0);
-        test_target("1.17", RustTarget::Stable_1_17);
-        test_target("1.19", RustTarget::Stable_1_19);
-        test_target("1.21", RustTarget::Stable_1_21);
-        test_target("1.25", RustTarget::Stable_1_25);
+    fn valid_targets() {
         test_target("1.71", RustTarget::Stable_1_71);
+        test_target("1.71.0", RustTarget::Stable_1_71);
+        test_target("1.71.1", RustTarget::Stable_1_71);
+        test_target("1.72", RustTarget::Stable_1_71);
+        test_target("1.73", RustTarget::Stable_1_73);
+        test_target("1.18446744073709551615", LATEST_STABLE_RUST);
         test_target("nightly", RustTarget::Nightly);
     }
+
+    #[test]
+    fn invalid_targets() {
+        test_invalid_target("2.0");
+        test_invalid_target("1.cat");
+        test_invalid_target("1.0.cat");
+        test_invalid_target("1.18446744073709551616");
+        test_invalid_target("1.0.18446744073709551616");
+        test_invalid_target("1.-1.0");
+        test_invalid_target("1.0.-1");
+        test_invalid_target("beta");
+    }
 }