Feat: Index cheatcode for Strings (#7539)

* feat: index cheatcode

* some nits to make it work

* nit: use as_str()

* final changes

* chore: reviewed changes

crates/cheatcodes/spec/src/vm.rs

@@ -1680,6 +1680,11 @@ interface Vm {
     /// Splits the given `string` into an array of strings divided by the `delimiter`.
     #[cheatcode(group = String)]
     function split(string calldata input, string calldata delimiter) external pure returns (string[] memory outputs);
+    /// Returns the index of the first occurrence of a `key` in an `input` string.
+    /// Returns `NOT_FOUND` (i.e. `type(uint256).max`) if the `key` is not found.
+    /// Returns 0 in case of an empty `key`.
+    #[cheatcode(group = String)]
+    function indexOf(string memory input, string memory key) external pure returns (uint256);
 
     // ======== JSON Parsing and Manipulation ========
 

crates/cheatcodes/src/string.rs

@@ -2,6 +2,7 @@
 
 use crate::{Cheatcode, Cheatcodes, Result, Vm::*};
 use alloy_dyn_abi::{DynSolType, DynSolValue};
+use alloy_primitives::U256;
 use alloy_sol_types::SolValue;
 
 // address
@@ -135,6 +136,14 @@ impl Cheatcode for splitCall {
     }
 }
 
+// indexOf
+impl Cheatcode for indexOfCall {
+    fn apply(&self, _state: &mut Cheatcodes) -> Result {
+        let Self { input, key } = self;
+        Ok(input.find(key).map(U256::from).unwrap_or(U256::MAX).abi_encode())
+    }
+}
+
 pub(super) fn parse(s: &str, ty: &DynSolType) -> Result {
     parse_value(s, ty).map(|v| v.abi_encode())
 }

testdata/default/cheats/StringUtils.t.sol

@@ -39,4 +39,16 @@ contract StringManipulationTest is DSTest {
         assertEq("World", splitResult[1]);
         assertEq("Reth", splitResult[2]);
     }
+
+    function testIndexOf() public {
+        string memory input = "Hello, World!";
+        string memory key1 = "Hello,";
+        string memory key2 = "World!";
+        string memory key3 = "";
+        string memory key4 = "foundry";
+        assertEq(vm.indexOf(input, key1), 0);
+        assertEq(vm.indexOf(input, key2), 7);
+        assertEq(vm.indexOf(input, key3), 0);
+        assertEq(vm.indexOf(input, key4), type(uint256).max);
+    }
 }