api: Replace Display implementation of MatrixVersion with as_str() method

Because it is not correct to convert V1_0 to a string.

crates/ruma-common/CHANGELOG.md

@@ -1,5 +1,30 @@
 # [unreleased]
 
+=======
+Breaking changes:
+
+- `UserId` parsing and deserialization are now compatible with all non-compliant
+  user IDs in the wild by default, due to a clarification in the spec.
+  - The `compat-user-id` cargo feature was removed.
+  - `UserId::validate_historical()` and `UserId::validate_strict()` allow to
+    check for spec compliance.
+  - The `(owned_)user_id!` macros always validate against the strict grammar in
+    the spec, regardless of the compat features that are enabled.
+- `(owned_)room_id!` macros disallow the `NUL` byte, due to a clarification in
+  the spec.
+- `(owned_)room_alias_id!` macros disallow the `NUL` byte for the localpart, due
+  to a clarification in the spec.
+- `MatrixVersion` does not implement `Display` anymore as it is not correct to
+  convert `V1_0` to a string. Instead `MatrixVersion::as_str()` can be used that
+  only returns `None` for that same variant.
+
+Improvements:
+
+- `MatrixVersion` implements `PartialOrd` and `Ord`. The variants are ordered by
+  release date, with a newer version being greater than an older version.
+
+# 0.15.1
+
 Improvements:
 
 - Add `MatrixVersion::V1_13`.

crates/ruma-common/src/api/error.rs

@@ -113,7 +113,10 @@ pub enum IntoHttpError {
 
     /// Tried to create a request with [`MatrixVersion`]s for all of which this endpoint was
     /// removed.
-    #[error("could not create any path variant for endpoint, as it was removed in version {0}")]
+    #[error(
+        "could not create any path variant for endpoint, as it was removed in version {}",
+        .0.as_str().expect("no endpoint was removed in Matrix 1.0")
+    )]
     EndpointRemoved(MatrixVersion),
 
     /// JSON serialization failed.

crates/ruma-common/src/api/metadata.rs

@@ -1,6 +1,6 @@
 use std::{
     cmp::Ordering,
-    fmt::{self, Display, Write},
+    fmt::{Display, Write},
     str::FromStr,
 };
 
@@ -631,6 +631,33 @@ impl MatrixVersion {
         self >= other
     }
 
+    /// Get a string representation of this Matrix version.
+    ///
+    /// This is the string that can be found in the response to one of the `GET /versions`
+    /// endpoints. Parsing this string will give the same variant.
+    ///
+    /// Returns `None` for [`MatrixVersion::V1_0`] because it can match several per-API versions.
+    pub const fn as_str(self) -> Option<&'static str> {
+        let string = match self {
+            MatrixVersion::V1_0 => return None,
+            MatrixVersion::V1_1 => "v1.1",
+            MatrixVersion::V1_2 => "v1.2",
+            MatrixVersion::V1_3 => "v1.3",
+            MatrixVersion::V1_4 => "v1.4",
+            MatrixVersion::V1_5 => "v1.5",
+            MatrixVersion::V1_6 => "v1.6",
+            MatrixVersion::V1_7 => "v1.7",
+            MatrixVersion::V1_8 => "v1.8",
+            MatrixVersion::V1_9 => "v1.9",
+            MatrixVersion::V1_10 => "v1.10",
+            MatrixVersion::V1_11 => "v1.11",
+            MatrixVersion::V1_12 => "v1.12",
+            MatrixVersion::V1_13 => "v1.13",
+        };
+
+        Some(string)
+    }
+
     /// Decompose the Matrix version into its major and minor number.
     pub const fn into_parts(self) -> (u8, u8) {
         match self {
@@ -773,13 +800,6 @@ impl MatrixVersion {
     }
 }
 
-impl Display for MatrixVersion {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let (major, minor) = self.into_parts();
-        f.write_str(&format!("v{major}.{minor}"))
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use assert_matches2::assert_matches;
@@ -906,4 +926,15 @@ mod tests {
 
         assert_eq!(LIT, V1_0);
     }
+
+    #[test]
+    fn parse_as_str_sanity() {
+        let version = MatrixVersion::try_from("r0.5.0").unwrap();
+        assert_eq!(version, V1_0);
+        assert_eq!(version.as_str(), None);
+
+        let version = MatrixVersion::try_from("v1.1").unwrap();
+        assert_eq!(version, V1_1);
+        assert_eq!(version.as_str(), Some("v1.1"));
+    }
 }