Make predicate w. missing capture return true

If a predicate in a query references a capture that was not matched
because it was optional in the query, return true rather than throw an
error. In other words, if the capture was not found, ignore the
predicate entirely.

This matches the behavior of tree-sitter CLI and the playground. It
 is not a common case but we have run into the issue matching Kotlin functions
where the return type of a function is optional in the grammar requiring
us to do additional filtering in the app code after the query.

tests/test_tree_sitter.py

@@ -1432,6 +1432,55 @@ def test_text_predicates(self):
         self.assertEqual(2, len(captures_notext))
         self.assertSetEqual({"function-name"}, set([c[1] for c in captures_notext]))
 
+    def test_text_predicate_on_optional_capture(self):
+        parser = Parser()
+        parser.set_language(JAVASCRIPT)
+        source = b"fun1(1)"
+        tree = parser.parse(source)
+        root_node = tree.root_node
+
+        # optional capture that is missing in source used in #eq? @capture string
+        query1 = JAVASCRIPT.query(
+            """
+            ((call_expression
+                function: (identifier) @function-name
+                arguments: (arguments (string)? @optional-string-arg)
+                (#eq? @optional-string-arg "1")))
+            """
+        )
+        captures1 = query1.captures(root_node)
+        self.assertEqual(1, len(captures1))
+        self.assertEqual(b"fun1", captures1[0][0].text)
+        self.assertEqual("function-name", captures1[0][1])
+
+        # optional capture that is missing in source used in #eq? @capture @capture
+        query2 = JAVASCRIPT.query(
+            """
+            ((call_expression
+                function: (identifier) @function-name
+                arguments: (arguments (string)? @optional-string-arg)
+                (#eq? @optional-string-arg @function-name)))
+            """
+        )
+        captures2 = query2.captures(root_node)
+        self.assertEqual(1, len(captures2))
+        self.assertEqual(b"fun1", captures2[0][0].text)
+        self.assertEqual("function-name", captures2[0][1])
+
+        # optional capture that is missing in source used in #match? @capture string
+        query3 = JAVASCRIPT.query(
+            """
+            ((call_expression
+                function: (identifier) @function-name
+                arguments: (arguments (string)? @optional-string-arg)
+                (#match? @optional-string-arg "\\d+")))
+            """
+        )
+        captures3 = query3.captures(root_node)
+        self.assertEqual(1, len(captures3))
+        self.assertEqual(b"fun1", captures3[0][0].text)
+        self.assertEqual("function-name", captures3[0][1])
+
     def test_text_predicates_errors(self):
         parser = Parser()
         parser.set_language(JAVASCRIPT)

tree_sitter/binding.c

@@ -1853,7 +1853,6 @@ static Node *node_for_capture_index(ModuleState *state, uint32_t index, TSQueryM
             return capture_node;
         }
     }
-    PyErr_SetString(PyExc_ValueError, "An error occurred, capture was not found with given index");
     return NULL;
 }
 
@@ -1879,36 +1878,38 @@ static bool satisfies_text_predicates(Query *query, TSQueryMatch match, Tree *tr
             node1 = node_for_capture_index(state, capture1_value_id, match, tree);
             node2 = node_for_capture_index(state, capture2_value_id, match, tree);
             if (node1 == NULL || node2 == NULL) {
-                goto error;
-            }
-            node1_text = node_get_text(node1, NULL);
-            node2_text = node_get_text(node2, NULL);
-            if (node1_text == NULL || node2_text == NULL) {
-                goto error;
+                is_satisfied = true;
+            } else {
+                node1_text = node_get_text(node1, NULL);
+                node2_text = node_get_text(node2, NULL);
+                if (node1_text == NULL || node2_text == NULL) {
+                    goto error;
+                }
+                is_satisfied = PyObject_RichCompareBool(node1_text, node2_text, Py_EQ) ==
+                               ((CaptureEqCapture *)text_predicate)->is_positive;
+                Py_XDECREF(node1);
+                Py_XDECREF(node2);
+                Py_XDECREF(node1_text);
+                Py_XDECREF(node2_text);
             }
-            Py_XDECREF(node1);
-            Py_XDECREF(node2);
-            is_satisfied = PyObject_RichCompareBool(node1_text, node2_text, Py_EQ) ==
-                           ((CaptureEqCapture *)text_predicate)->is_positive;
-            Py_XDECREF(node1_text);
-            Py_XDECREF(node2_text);
             if (!is_satisfied) {
                 return false;
             }
         } else if (capture_eq_string_is_instance(text_predicate)) {
             uint32_t capture_value_id = ((CaptureEqString *)text_predicate)->capture_value_id;
             node1 = node_for_capture_index(state, capture_value_id, match, tree);
             if (node1 == NULL) {
-                goto error;
-            }
-            node1_text = node_get_text(node1, NULL);
-            if (node1_text == NULL) {
-                goto error;
+                is_satisfied = true;
+            } else {
+                node1_text = node_get_text(node1, NULL);
+                if (node1_text == NULL) {
+                    goto error;
+                }
+                PyObject *string_value = ((CaptureEqString *)text_predicate)->string_value;
+                is_satisfied = PyObject_RichCompareBool(node1_text, string_value, Py_EQ) ==
+                               ((CaptureEqString *)text_predicate)->is_positive;
             }
             Py_XDECREF(node1);
-            PyObject *string_value = ((CaptureEqString *)text_predicate)->string_value;
-            is_satisfied = PyObject_RichCompareBool(node1_text, string_value, Py_EQ) ==
-                           ((CaptureEqString *)text_predicate)->is_positive;
             Py_XDECREF(node1_text);
             if (!is_satisfied) {
                 return false;
@@ -1917,22 +1918,23 @@ static bool satisfies_text_predicates(Query *query, TSQueryMatch match, Tree *tr
             uint32_t capture_value_id = ((CaptureMatchString *)text_predicate)->capture_value_id;
             node1 = node_for_capture_index(state, capture_value_id, match, tree);
             if (node1 == NULL) {
-                goto error;
-            }
-            node1_text = node_get_text(node1, NULL);
-            if (node1_text == NULL) {
-                goto error;
+                is_satisfied = true;
+            } else {
+                node1_text = node_get_text(node1, NULL);
+                if (node1_text == NULL) {
+                    goto error;
+                }
+                PyObject *search_result =
+                    PyObject_CallMethod(((CaptureMatchString *)text_predicate)->regex, "search",
+                                        "s", PyBytes_AsString(node1_text));
+                Py_XDECREF(node1_text);
+                is_satisfied = (search_result != NULL && search_result != Py_None) ==
+                               ((CaptureMatchString *)text_predicate)->is_positive;
+                if (search_result != NULL) {
+                    Py_DECREF(search_result);
+                }
             }
             Py_XDECREF(node1);
-            PyObject *search_result =
-                PyObject_CallMethod(((CaptureMatchString *)text_predicate)->regex, "search", "s",
-                                    PyBytes_AsString(node1_text));
-            Py_XDECREF(node1_text);
-            is_satisfied = (search_result != NULL && search_result != Py_None) ==
-                           ((CaptureMatchString *)text_predicate)->is_positive;
-            if (search_result != NULL) {
-                Py_DECREF(search_result);
-            }
             if (!is_satisfied) {
                 return false;
             }