bind-gen: Improve ListNode to insert head and tail if not empty

Makes ListNode insert the head and tail section iff the content
is not empty.

Bug: 839389
Change-Id: Ie154a6f252814abc3a51284f22ac04188e168e00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1981417Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727541}

third_party/blink/renderer/bindings/scripts/bind_gen/code_node.py

@@ -432,25 +432,40 @@ class ListNode(CodeNode):
     except that addition and removal of None have no effect.
     """
 
-    def __init__(self, code_nodes=None, separator="\n", separator_last=""):
+    def __init__(self, code_nodes=None, separator="\n", head="", tail=""):
+        """
+        Args:
+            code_nodes: A list of CodeNode to be rendered.
+            separator: A str inserted between code nodes.
+            head:
+            tail: The head and tail sections that will be rendered iff the
+                content list is not empty.
+        """
         assert isinstance(separator, str)
-        assert isinstance(separator_last, str)
+        assert isinstance(head, str)
+        assert isinstance(tail, str)
 
         element_nodes_gensym = CodeNode.gensym()
         element_nodes = []
         template_text = format_template(
             """\
+% if {element_nodes}:
+{head}\\
+% endif
 % for node in {element_nodes}:
 ${node}\\
 % if not loop.last:
 {separator}\\
 % endif
 % endfor
-{separator_last}\
+% if {element_nodes}:
+{tail}\\
+% endif\
 """,
             element_nodes=element_nodes_gensym,
             separator=separator,
-            separator_last=separator_last)
+            head=head,
+            tail=tail)
         template_vars = {element_nodes_gensym: element_nodes}
 
         CodeNode.__init__(
@@ -530,12 +545,13 @@ class SequenceNode(ListNode):
     and provides the points where SymbolDefinitionNodes can be inserted.
     """
 
-    def __init__(self, code_nodes=None, separator="\n", separator_last=""):
+    def __init__(self, code_nodes=None, separator="\n", head="", tail=""):
         ListNode.__init__(
             self,
             code_nodes=code_nodes,
             separator=separator,
-            separator_last=separator_last)
+            head=head,
+            tail=tail)
 
     def _render(self, renderer, last_render_state):
         duplicates = []
@@ -558,12 +574,13 @@ class SymbolScopeNode(SequenceNode):
     insert corresponding SymbolDefinitionNodes appropriately.
     """
 
-    def __init__(self, code_nodes=None, separator="\n", separator_last=""):
+    def __init__(self, code_nodes=None, separator="\n", head="", tail=""):
         SequenceNode.__init__(
             self,
             code_nodes=code_nodes,
             separator=separator,
-            separator_last=separator_last)
+            head=head,
+            tail=tail)
 
         self._likeliness = Likeliness.ALWAYS
         self._registered_code_symbols = set()

third_party/blink/renderer/bindings/scripts/bind_gen/code_node_cxx_test.py

@@ -33,7 +33,7 @@ class CodeNodeCxxTest(unittest.TestCase):
         self.assertEqual(actual, expected)
 
     def test_symbol_definition_with_branches(self):
-        root = SymbolScopeNode(separator_last="\n")
+        root = SymbolScopeNode(tail="\n")
 
         root.register_code_symbols([
             SymbolNode("var1", "int ${var1} = 1;"),
@@ -79,7 +79,7 @@ var3;
 """)
 
     def test_symbol_definition_with_nested_branches(self):
-        root = SymbolScopeNode(separator_last="\n")
+        root = SymbolScopeNode(tail="\n")
 
         root.register_code_symbols([
             SymbolNode("var1", "int ${var1} = 1;"),
@@ -132,7 +132,7 @@ if (true) {
 """)
 
     def test_function_definition_minimum(self):
-        root = SymbolScopeNode(separator_last="\n")
+        root = SymbolScopeNode(tail="\n")
         root.append(
             CxxFuncDefNode(
                 name="blink::bindings::func", arg_decls=[],
@@ -145,7 +145,7 @@ void blink::bindings::func() {
 """)
 
     def test_function_definition_full(self):
-        root = SymbolScopeNode(separator_last="\n")
+        root = SymbolScopeNode(tail="\n")
 
         func_def = CxxFuncDefNode(
             name="blink::bindings::func",

third_party/blink/renderer/bindings/scripts/bind_gen/code_node_test.py

@@ -72,6 +72,14 @@ class CodeNodeTest(unittest.TestCase):
         root.remove(root[-1])
         self.assertRenderResult(root, "2,3,5")
 
+    def test_list_node_head_and_tail(self):
+        self.assertRenderResult(ListNode(), "")
+        self.assertRenderResult(ListNode(head="head"), "")
+        self.assertRenderResult(ListNode(tail="tail"), "")
+        self.assertRenderResult(
+            ListNode([TextNode("-content-")], head="head", tail="tail"),
+            "head-content-tail")
+
     def test_nested_sequence(self):
         """Tests nested ListNodes."""
         root = ListNode(separator=",")
@@ -93,7 +101,7 @@ class CodeNodeTest(unittest.TestCase):
         Tests that use of SymbolNode inserts necessary SymbolDefinitionNode
         appropriately.
         """
-        root = SymbolScopeNode(separator_last="\n")
+        root = SymbolScopeNode(tail="\n")
 
         root.register_code_symbols([
             SymbolNode("var1", "int ${var1} = ${var2} + ${var3};"),

third_party/blink/renderer/bindings/scripts/bind_gen/dictionary.py

@@ -637,7 +637,7 @@ def generate_dictionary_cc_file(dictionary):
             make_dict_member_set_def(cg_context.make_copy(dict_member=member)),
         ])
 
-    root_node = SymbolScopeNode(separator_last="\n")
+    root_node = ListNode(tail="\n")
     root_node.set_accumulator(CodeGenAccumulator())
     root_node.set_renderer(MakoRenderer())
 
@@ -681,7 +681,7 @@ def generate_dictionary_h_file(dictionary):
         make_dict_class_def(cg_context),
     ])
 
-    root_node = SymbolScopeNode(separator_last="\n")
+    root_node = ListNode(tail="\n")
     root_node.set_accumulator(CodeGenAccumulator())
     root_node.set_renderer(MakoRenderer())