eval: restore context pointer of first evaluated dot/bracket expression

When an expression such as `foo.bar(a.b, c.d)` is evaluated, the state
context pointer will point to `c` while we need `foo` when invoking
functions.

Since the context pointer is only relevant for function calls and since
for function call opcodes, the lhs expression is always the first operand,
there is no need to store the context of subsequent ops.

Adjust the ut_get_operands() procedure to restore state->ctx to the result
of the first evaluated operand.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

2 files changed, 31 insertions, 0 deletions

diff --git a/eval.c b/eval.c
index 1803355..074baa5 100644
--- a/eval.c
+++ b/eval.c
@@ -746,6 +746,7 @@ ut_cmp(int how, struct json_object *v1, struct json_object *v2)
 static struct json_object *
 _ut_get_operands(struct ut_state *state, struct ut_op *op, size_t n, struct json_object **v)
 {
+	struct json_object *ctx = NULL;
 	struct ut_op *child;
 	size_t i, j;
 
@@ -759,7 +760,12 @@ _ut_get_operands(struct ut_state *state, struct ut_op *op, size_t n, struct json
 		else
 			v[i] = NULL;
 
+		if (i == 0)
+			ctx = json_object_get(state->ctx);
+
 		if (ut_is_type(v[i], T_EXCEPTION)) {
+			json_object_put(ctx);
+
 			for (j = 0; j < i; j++)
 				json_object_put(v[j]);
 
@@ -767,6 +773,9 @@ _ut_get_operands(struct ut_state *state, struct ut_op *op, size_t n, struct json
 		}
 	}
 
+	json_object_put(state->ctx);
+	state->ctx = ctx;
+
 	return NULL;
 }
 
diff --git a/tests/02_runtime/02_this b/tests/02_runtime/02_this
index d41be7f..e1efd80 100644
--- a/tests/02_runtime/02_this
+++ b/tests/02_runtime/02_this
@@ -23,3 +23,25 @@ true
 	print(o.test(), "\n");
 %}
 -- End --
+
+Test that the context is properly restored if function call arguments are
+dot or bracket expressions as well.
+
+-- Expect stdout --
+true
+true
+-- End --
+
+-- Testcase --
+{%
+	local o = {
+		test: function() {
+			return (this === o);
+		}
+	};
+
+	local dummy = { foo: true, bar: false };
+
+	print(o.test(dummy.foo, dummy.bar), "\n");
+	print(o.test(dummy.foo, o.test(dummy.foo, dummy.bar)), "\n");
+%}