Add Secret::map

README.md

@@ -27,6 +27,17 @@ let encryption_key = Secret::new("hello world");
 assert_eq!("hello world", *encryption_key.expose_secret())
 ```
 
+The secret may alternatively be transformed into another secret value
+using the [map][Secret::map] method, which acts similarly to
+[Option::map][Option::map].
+
+```rust
+use redact::Secret;
+
+let encryption_key = Secret::new("hello world").map(str::to_string);
+assert_eq!("hello world", *encryption_key.expose_secret())
+```
+
 The `Secret` type doubles as a useful documentation tool.
 Documenting values maintainers should be careful with.
 

src/lib.rs

@@ -45,6 +45,15 @@ impl<T> Secret<T> {
     pub const fn expose_secret(&self) -> &T {
         &self.0
     }
+    /// See [module level documentation][crate]
+    #[inline]
+    #[must_use = "the secret will be dropped if not used"]
+    pub fn map<F, U>(self, mapper: F) -> Secret<U>
+    where
+        F: FnOnce(T) -> U,
+    {
+        Secret::new(mapper(self.0))
+    }
 }
 
 impl<T> From<T> for Secret<T> {