lib: add fromHexString tests for distressing behaviour

emilazy · emilazy · commit 6673e05ad065 · 2025-08-14T21:02:11.000+01:00
This was cherry‐picked from <#266705> and merged as part of <#318712>, despite there being a blocking review on the former pointing out these kinds of issues. This documents some of the dodgy behaviour. It also can’t handle negative literals. It might be worth considering deprecating and dropping this, by inlining it into `lib.network.ipv6.fromString`, its only in‐tree user.
diff --git a/lib/tests/misc.nix b/lib/tests/misc.nix
@@ -390,6 +390,30 @@ runTests {
     expected = 15;
   };
 
+  # FIXME: This might be bad and should potentially be deprecated.
+  testFromHexStringQuestionableMixedCase = {
+    expr = fromHexString "eEeEe";
+    expected = 978670;
+  };
+
+  # FIXME: This is probably bad and should potentially be deprecated.
+  testFromHexStringQuestionableUnderscore = {
+    expr = fromHexString "F_f";
+    expected = 255;
+  };
+
+  # FIXME: This is definitely bad and should be deprecated.
+  testFromHexStringBadComment = {
+    expr = fromHexString "0 # oops";
+    expected = 0;
+  };
+
+  # FIXME: Oh my god.
+  testFromHexStringAwfulInjection = {
+    expr = fromHexString "1\nwhoops = {}";
+    expected = 1;
+  };
+
   testToBaseDigits = {
     expr = toBaseDigits 2 6;
     expected = [
