Test case added, API output asserted, output format slightly changed

slither/analyses/data_dependency/data_dependency.py

@@ -302,9 +302,8 @@ def get_must_depends_on(variable: SUPPORTED_TYPES) -> SUPPORTED_TYPES | None:
     """
     must_dependencies = compute_must_dependencies(variable)
     if len(must_dependencies) > 1 or len(must_dependencies) == 0:
-        return None
-    return list(must_dependencies)[0]
-
+        return []
+    return [list(must_dependencies)[0]]
 
 def compute_must_dependencies(v:SUPPORTED_TYPES) -> Set[Variable]:
     if isinstance(v, (SolidityVariableComposed, Constant)) or (

tests/unit/core/test_data/must_depend_on.sol

@@ -0,0 +1,29 @@
+pragma solidity ^0.8.19;
+
+interface IERC20 {
+  function transferFrom(address from, address to, uint amount) external returns (bool);
+}
+
+/**
+ * @title MissingReturnBug
+ * @author IllIllI
+ */
+
+// test case of the missing return bug described here:
+// https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca
+contract Unsafe {
+    IERC20 erc20;
+    function good2(address to, uint256 am) public {
+        address from_msgsender = msg.sender;
+        int_transferFrom(from_msgsender, to, am); // from is constant
+    }
+
+    // This is not detected
+    function bad2(address from, address to, uint256 am) public {
+        int_transferFrom(from, to, amount); // from is not a constant
+    }
+
+    function int_transferFrom(address from, address to, uint256 amount) internal {
+        erc20.transferFrom(from, to, amount); // not a constant = not a constant U constant
+    }
+}

tests/unit/core/test_must_depend_on.py

@@ -0,0 +1,14 @@
+from pathlib import Path
+from slither import Slither
+from slither.analyses.data_dependency.data_dependency import (
+    get_must_depends_on
+)
+
+TEST_DATA_DIR = Path(__file__).resolve().parent / "test_data"
+
+def test_must_depend_on_returns(solc_binary_path):
+    solc_path = solc_binary_path("0.8.19")
+    file = Path(TEST_DATA_DIR, "must_depend_on.sol").as_posix()
+    slither_obj = Slither(file, solc=solc_path)
+    result = get_must_depends_on(slither_obj.contracts[1].functions[2].parameters[0])
+    assert isinstance(result, list) and len(result) <= 1