Move get_short_name utility method from bevy_reflect into bevy_utils (#5174)

# Summary

This method strips a long type name like `bevy::render:📷:PerspectiveCameraBundle` down into the bare type name (`PerspectiveCameraBundle`). This is generally useful utility method, needed by #4299 and #5121.

As a result:

- This method was moved to `bevy_utils` for easier reuse.
- The legibility and robustness of this method has been significantly improved.
- Harder test cases have been added.

This change was split out of #4299 to unblock it and make merging / reviewing the rest of those changes easier.

## Changelog

- added `bevy_utils::get_short_name`, which strips the path from a type name for convenient display.
- removed the `TypeRegistry::get_short_name` method. Use the function in `bevy_utils` instead.

crates/bevy_reflect/src/type_registry.rs

@@ -231,7 +231,7 @@ impl TypeRegistryArc {
 /// a [`TypeData`] which can be used to downcast [`Reflect`] trait objects of
 /// this type to trait objects of the relevant trait.
 ///
-/// [short name]: TypeRegistration::get_short_name
+/// [short name]: bevy_utils::get_short_name
 /// [`TypeInfo`]: crate::TypeInfo
 /// [0]: crate::Reflect
 /// [1]: crate::Reflect
@@ -287,14 +287,14 @@ impl TypeRegistration {
         let type_name = std::any::type_name::<T>();
         Self {
             data: HashMap::default(),
-            short_name: Self::get_short_name(type_name),
+            short_name: bevy_utils::get_short_name(type_name),
             type_info: T::type_info(),
         }
     }
 
     /// Returns the [short name] of the type.
     ///
-    /// [short name]: TypeRegistration::get_short_name
+    /// [short name]: bevy_utils::get_short_name
     pub fn short_name(&self) -> &str {
         &self.short_name
     }
@@ -305,49 +305,6 @@ impl TypeRegistration {
     pub fn type_name(&self) -> &'static str {
         self.type_info.type_name()
     }
-
-    /// Calculates the short name of a type.
-    ///
-    /// The short name of a type is its full name as returned by
-    /// [`std::any::type_name`], but with the prefix of all paths removed. For
-    /// example, the short name of `alloc::vec::Vec<core::option::Option<u32>>`
-    /// would be `Vec<Option<u32>>`.
-    pub fn get_short_name(full_name: &str) -> String {
-        let mut short_name = String::new();
-
-        {
-            // A typename may be a composition of several other type names (e.g. generic parameters)
-            // separated by the characters that we try to find below.
-            // Then, each individual typename is shortened to its last path component.
-            //
-            // Note: Instead of `find`, `split_inclusive` would be nice but it's still unstable...
-            let mut remainder = full_name;
-            while let Some(index) = remainder.find(&['<', '>', '(', ')', '[', ']', ',', ';'][..]) {
-                let (path, new_remainder) = remainder.split_at(index);
-                // Push the shortened path in front of the found character
-                short_name.push_str(path.rsplit(':').next().unwrap());
-                // Push the character that was found
-                let character = new_remainder.chars().next().unwrap();
-                short_name.push(character);
-                // Advance the remainder
-                if character == ',' || character == ';' {
-                    // A comma or semicolon is always followed by a space
-                    short_name.push(' ');
-                    remainder = &new_remainder[2..];
-                } else {
-                    remainder = &new_remainder[1..];
-                }
-            }
-
-            // The remainder will only be non-empty if there were no matches at all
-            if !remainder.is_empty() {
-                // Then, the full typename is a path that has to be shortened
-                short_name.push_str(remainder.rsplit(':').next().unwrap());
-            }
-        }
-
-        short_name
-    }
 }
 
 impl Clone for TypeRegistration {
@@ -459,42 +416,6 @@ mod test {
     use crate::TypeRegistration;
     use bevy_utils::HashMap;
 
-    #[test]
-    fn test_get_short_name() {
-        assert_eq!(
-            TypeRegistration::get_short_name(std::any::type_name::<f64>()),
-            "f64"
-        );
-        assert_eq!(
-            TypeRegistration::get_short_name(std::any::type_name::<String>()),
-            "String"
-        );
-        assert_eq!(
-            TypeRegistration::get_short_name(std::any::type_name::<(u32, f64)>()),
-            "(u32, f64)"
-        );
-        assert_eq!(
-            TypeRegistration::get_short_name(std::any::type_name::<(String, String)>()),
-            "(String, String)"
-        );
-        assert_eq!(
-            TypeRegistration::get_short_name(std::any::type_name::<[f64]>()),
-            "[f64]"
-        );
-        assert_eq!(
-            TypeRegistration::get_short_name(std::any::type_name::<[String]>()),
-            "[String]"
-        );
-        assert_eq!(
-            TypeRegistration::get_short_name(std::any::type_name::<[f64; 16]>()),
-            "[f64; 16]"
-        );
-        assert_eq!(
-            TypeRegistration::get_short_name(std::any::type_name::<[String; 16]>()),
-            "[String; 16]"
-        );
-    }
-
     #[test]
     fn test_property_type_registration() {
         assert_eq!(

crates/bevy_utils/src/lib.rs

@@ -4,6 +4,8 @@ pub mod prelude {
 
 pub mod futures;
 pub mod label;
+mod short_names;
+pub use short_names::get_short_name;
 
 mod default;
 mod float_ord;

crates/bevy_utils/src/short_names.rs

@@ -0,0 +1,110 @@
+/// Shortens a type name to remove all module paths.
+///
+/// The short name of a type is its full name as returned by
+/// [`std::any::type_name`], but with the prefix of all paths removed. For
+/// example, the short name of `alloc::vec::Vec<core::option::Option<u32>>`
+/// would be `Vec<Option<u32>>`.
+pub fn get_short_name(full_name: &str) -> String {
+    // Generics result in nested paths within <..> blocks.
+    // Consider "bevy_render::camera::camera::extract_cameras<bevy_render::camera::bundle::Camera3d>".
+    // To tackle this, we parse the string from left to right, collapsing as we go.
+    let mut index: usize = 0;
+    let end_of_string = full_name.len();
+    let mut parsed_name = String::new();
+
+    while index < end_of_string {
+        let rest_of_string = full_name.get(index..end_of_string).unwrap_or_default();
+
+        // Collapse everything up to the next special character,
+        // then skip over it
+        if let Some(special_character_index) = rest_of_string.find(|c: char| {
+            (c == ' ')
+                || (c == '<')
+                || (c == '>')
+                || (c == '(')
+                || (c == ')')
+                || (c == '[')
+                || (c == ']')
+                || (c == ',')
+                || (c == ';')
+        }) {
+            let segment_to_collapse = rest_of_string
+                .get(0..special_character_index)
+                .unwrap_or_default();
+            parsed_name += collapse_type_name(segment_to_collapse);
+            // Insert the special character
+            let special_character =
+                &rest_of_string[special_character_index..=special_character_index];
+            parsed_name.push_str(special_character);
+            // Move the index just past the special character
+            index += special_character_index + 1;
+        } else {
+            // If there are no special characters left, we're done!
+            parsed_name += collapse_type_name(rest_of_string);
+            index = end_of_string;
+        }
+    }
+    parsed_name
+}
+
+#[inline(always)]
+fn collapse_type_name(string: &str) -> &str {
+    string.split("::").last().unwrap()
+}
+
+#[cfg(test)]
+mod name_formatting_tests {
+    use super::get_short_name;
+
+    #[test]
+    fn trivial() {
+        assert_eq!(get_short_name("test_system"), "test_system");
+    }
+
+    #[test]
+    fn path_seperated() {
+        assert_eq!(
+            get_short_name("bevy_prelude::make_fun_game"),
+            "make_fun_game".to_string()
+        );
+    }
+
+    #[test]
+    fn tuple_type() {
+        assert_eq!(
+            get_short_name("(String, String)"),
+            "(String, String)".to_string()
+        );
+    }
+
+    #[test]
+    fn array_type() {
+        assert_eq!(get_short_name("[i32; 3]"), "[i32; 3]".to_string());
+    }
+
+    #[test]
+    fn trivial_generics() {
+        assert_eq!(get_short_name("a<B>"), "a<B>".to_string());
+    }
+
+    #[test]
+    fn multiple_type_parameters() {
+        assert_eq!(get_short_name("a<B, C>"), "a<B, C>".to_string());
+    }
+
+    #[test]
+    fn generics() {
+        assert_eq!(
+            get_short_name("bevy_render::camera::camera::extract_cameras<bevy_render::camera::bundle::Camera3d>"),
+            "extract_cameras<Camera3d>".to_string()
+        );
+    }
+
+    #[test]
+    fn nested_generics() {
+        assert_eq!(
+            get_short_name("bevy::mad_science::do_mad_science<mad_science::Test<mad_science::Tube>, bavy::TypeSystemAbuse>"),
+            "do_mad_science<Test<Tube>, TypeSystemAbuse>".to_string()
+        );
+    }
+}

tools/spancmp/Cargo.toml

@@ -12,5 +12,5 @@ serde = { version = "1.0", features = ["derive"] }
 clap = { version = "3.2", features = ["derive"] }
 regex = "1.5"
 termcolor = "1.1"
-bevy_reflect = { path = "../../crates/bevy_reflect", version = "0.8.0-dev" }
+bevy_utils = { path = "../../crates/bevy_utils", version = "0.8.0-dev" }
 lazy_static = "1.4"

tools/spancmp/src/pretty.rs

@@ -1,4 +1,4 @@
-use bevy_reflect::TypeRegistration;
+use bevy_utils::get_short_name;
 use lazy_static::lazy_static;
 use regex::Regex;
 use termcolor::{Color, ColorSpec, StandardStream, WriteColor};
@@ -206,21 +206,18 @@ lazy_static! {
 
 pub fn simplify_name(name: &str) -> String {
     if let Some(captures) = SYSTEM_NAME.captures(name) {
-        return format!(
+        return format!(r#"system: name="{}""#, get_short_name(&captures[1]));
-            r#"system: name="{}""#,
-            TypeRegistration::get_short_name(&captures[1])
-        );
     }
     if let Some(captures) = SYSTEM_OVERHEAD.captures(name) {
         return format!(
             r#"system overhead: name="{}""#,
-            TypeRegistration::get_short_name(&captures[1])
+            get_short_name(&captures[1])
         );
     }
     if let Some(captures) = SYSTEM_COMMANDS.captures(name) {
         return format!(
             r#"system_commands: name="{}""#,
-            TypeRegistration::get_short_name(&captures[1])
+            get_short_name(&captures[1])
         );
     }
     name.to_string()