fix: `leptos_router::params_map!` (#1973)

Fixing implementation comes with the benefit of knocking a crate out of
the deps tree (`common_macros`).

router/Cargo.toml

@@ -14,7 +14,6 @@ leptos_integration_utils = { workspace = true, optional = true }
 leptos_meta = { workspace = true, optional = true }
 cached = { version = "0.45.0", optional = true }
 cfg-if = "1"
-common_macros = "0.1"
 gloo-net = { version = "0.2", features = ["http"] }
 lazy_static = "1"
 linear-map = { version = "1", features = ["serde_impl"] }

router/src/history/params.rs

@@ -72,31 +72,41 @@ impl Default for ParamsMap {
     }
 }
 
-/// A declarative way of creating a [`ParamsMap`].
+/// Create a [`ParamsMap`] in a declarative style.
 ///
 /// ```
 /// # use leptos_router::params_map;
 /// let map = params_map! {
-///     "id" => "1"
+///     "crate" => "leptos",
+///     42 => true, // where key & val: std::fmt::Display
 /// };
-/// assert_eq!(map.get("id"), Some(&"1".to_string()));
-/// assert_eq!(map.get("missing"), None)
+/// assert_eq!(map.get("crate"), Some(&"leptos".to_string()));
+/// assert_eq!(map.get("42"), Some(&true.to_string()))
 /// ```
+// Original implementation included the below credits.
+//
 // Adapted from hash_map! in common_macros crate
 // Copyright (c) 2019 Philipp Korber
 // https://github.com/rustonaut/common_macros/blob/master/src/lib.rs
 #[macro_export]
 macro_rules! params_map {
-    ($($key:expr => $val:expr),* ,) => (
-        $crate::ParamsMap!($($key => $val),*)
-    );
-    ($($key:expr => $val:expr),*) => ({
-        let start_capacity = common_macros::const_expr_count!($($key);*);
+    // Fast path avoids allocation.
+    () => { $crate::ParamsMap::with_capacity(0) };
+
+    // Counting repitions by n = 0 ( + 1 )*
+    //
+    // https://github.com/rust-lang/rust/issues/83527
+    // When stabilized you can use "metavaribale exprs" instead
+    //
+    // `$key | $val` must be included in the repetition to be valid, it is
+    // stringified to null out any possible side-effects.
+    ($($key:expr => $val:expr),* $(,)?) => {{
+        let n = 0 $(+ { _ = stringify!($key); 1 })*;
         #[allow(unused_mut)]
-        let mut map = linear_map::LinearMap::with_capacity(start_capacity);
+        let mut map = $crate::ParamsMap::with_capacity(n);
         $( map.insert($key.to_string(), $val.to_string()); )*
-        $crate::ParamsMap(map)
-    });
+        map
+    }};
 }
 
 /// A simple method of deserializing key-value data (like route params or URL search)