feat: Allow clearing an existing variable

crates/snapbox/src/substitutions.rs

@@ -63,6 +63,12 @@ impl Substitutions {
         Ok(())
     }
 
+    pub fn remove(&mut self, key: &'static str) -> Result<(), crate::Error> {
+        let key = validate_key(key)?;
+        self.vars.remove(key);
+        Ok(())
+    }
+
     /// Apply match pattern to `input`
     ///
     /// If `pattern` matches `input`, then `pattern` is returned.

src/cases.rs

@@ -143,7 +143,7 @@ impl TestCases {
 
     /// Batch add variables for normalizing output
     ///
-    /// See `insert_var`.
+    /// See [`insert_var`].
     pub fn extend_vars(
         &self,
         vars: impl IntoIterator<Item = (&'static str, impl Into<Cow<'static, str>>)>,
@@ -152,6 +152,14 @@ impl TestCases {
         Ok(self)
     }
 
+    /// Remove an existing var values
+    ///
+    /// See [`insert_var`].
+    pub fn clear_var(&self, var: &'static str) -> Result<&Self, crate::Error> {
+        self.substitutions.borrow_mut().remove(var)?;
+        Ok(self)
+    }
+
     /// Run tests
     ///
     /// This will happen on `drop` if not done explicitly