OptCheckStringFormat causes Program to fail generation if format argument has field access

[rodaine]

Describe the bug

With ext.Strings, setting the OptCheckStringFormat option when generating the Program fails if the argument to the format string refers to a field on a message.

To Reproduce

• parser
• checker
• interpreter

Test setup:

func Test(t *testing.T) {
	// message Msg {
	//   double fld = 1;
	// }
	msg := &Msg{Fld: 1.23}

	expr := "'%s'.format([msg.fld])"

	env, err := cel.NewEnv(
		ext.Strings(),
		cel.Types(msg),
		cel.Variable("msg",
			cel.ObjectType(string(msg.ProtoReflect().Descriptor().FullName()))),
	)
	require.NoError(t, err)

	ast, issues := env.Compile(expr)
	require.NoError(t, issues.Err())

	prog, err := env.Program(ast, cel.EvalOptions(
		cel.OptOptimize,
		cel.OptCheckStringFormat,
	))
	require.NoError(t, err)

	val, _, err := prog.Eval(map[string]any{"msg": msg})
	require.NoError(t, err)
	t.Logf("%#v", val)
}

Actual behavior

=== RUN   Test
    validator_test.go:59: 
        	Error:      	Received unexpected error:
        	            	error during formatting: string clause can only be used on strings, bools, bytes, ints, doubles, maps, lists, types, durations, and timestamps
--- FAIL: Test (0.00s)

Expected behavior

"1.23"

Additional context

Test passes with either modification:

• Remove cel.OptCheckStringFormat
• Replace msg type with cel.DynType

[TristonianJones]

@rodaine I'm not actually able to repro the error. I am curious though whether disabling cel.OptOptimize has any effect as I notice that the tests don't check this case.

[rodaine]

Removing just cel.OptOptimize from the above still fails with the same error. I think the above case is passing for you because the variable type is being set to Dyn. If you make it the explicit type of the message, you should see the same error.

[TristonianJones]

@rodaine Thank you, that was the piece I missed. My PR now reflects the fix and test case.