Add ast visitor for whitespaces and symbols

The `AstVisitor` intentionally ignores whitespaces and symbols,
as they are not useful for tne interpreter. However, when formatting a
build file, we need them. This commit introduces a `FullAstVisitor` that
visits every Nodes, including whitespaces and symbols.

mesonbuild/ast/visitor.py

@@ -6,6 +6,7 @@
 from __future__ import annotations
 
 import typing as T
+from itertools import zip_longest
 
 if T.TYPE_CHECKING:
     from .. import mparser
@@ -32,10 +33,10 @@ class AstVisitor:
     def visit_FormatStringNode(self, node: mparser.FormatStringNode) -> None:
         self.visit_default_func(node)
 
-    def visit_MultilineStringNode(self, node: mparser.MultilineFormatStringNode) -> None:
+    def visit_MultilineStringNode(self, node: mparser.MultilineStringNode) -> None:
         self.visit_default_func(node)
 
-    def visit_FormatMultilineStringNode(self, node: mparser.FormatStringNode) -> None:
+    def visit_FormatMultilineStringNode(self, node: mparser.MultilineFormatStringNode) -> None:
         self.visit_default_func(node)
 
     def visit_ContinueNode(self, node: mparser.ContinueNode) -> None:
@@ -159,3 +160,181 @@ class AstVisitor:
     def visit_ParenthesizedNode(self, node: mparser.ParenthesizedNode) -> None:
         self.visit_default_func(node)
         node.inner.accept(self)
+
+class FullAstVisitor(AstVisitor):
+    """Visit all nodes, including Symbol and Whitespaces"""
+
+    def enter_node(self, node: mparser.BaseNode) -> None:
+        pass
+
+    def exit_node(self, node: mparser.BaseNode) -> None:
+        if node.whitespaces:
+            node.whitespaces.accept(self)
+
+    def visit_default_func(self, node: mparser.BaseNode) -> None:
+        self.enter_node(node)
+        self.exit_node(node)
+
+    def visit_UnaryOperatorNode(self, node: mparser.UnaryOperatorNode) -> None:
+        self.enter_node(node)
+        node.operator.accept(self)
+        node.value.accept(self)
+        self.exit_node(node)
+
+    def visit_BinaryOperatorNode(self, node: mparser.BinaryOperatorNode) -> None:
+        self.enter_node(node)
+        node.left.accept(self)
+        node.operator.accept(self)
+        node.right.accept(self)
+        self.exit_node(node)
+
+    def visit_ArrayNode(self, node: mparser.ArrayNode) -> None:
+        self.enter_node(node)
+        node.lbracket.accept(self)
+        node.args.accept(self)
+        node.rbracket.accept(self)
+        self.exit_node(node)
+
+    def visit_DictNode(self, node: mparser.DictNode) -> None:
+        self.enter_node(node)
+        node.lcurl.accept(self)
+        node.args.accept(self)
+        node.rcurl.accept(self)
+        self.exit_node(node)
+
+    def visit_OrNode(self, node: mparser.OrNode) -> None:
+        self.visit_BinaryOperatorNode(node)
+
+    def visit_AndNode(self, node: mparser.AndNode) -> None:
+        self.visit_BinaryOperatorNode(node)
+
+    def visit_ComparisonNode(self, node: mparser.ComparisonNode) -> None:
+        self.visit_BinaryOperatorNode(node)
+
+    def visit_ArithmeticNode(self, node: mparser.ArithmeticNode) -> None:
+        self.visit_BinaryOperatorNode(node)
+
+    def visit_NotNode(self, node: mparser.NotNode) -> None:
+        self.visit_UnaryOperatorNode(node)
+
+    def visit_CodeBlockNode(self, node: mparser.CodeBlockNode) -> None:
+        self.enter_node(node)
+        if node.pre_whitespaces:
+            node.pre_whitespaces.accept(self)
+        for i in node.lines:
+            i.accept(self)
+        self.exit_node(node)
+
+    def visit_IndexNode(self, node: mparser.IndexNode) -> None:
+        self.enter_node(node)
+        node.iobject.accept(self)
+        node.lbracket.accept(self)
+        node.index.accept(self)
+        node.rbracket.accept(self)
+        self.exit_node(node)
+
+    def visit_MethodNode(self, node: mparser.MethodNode) -> None:
+        self.enter_node(node)
+        node.source_object.accept(self)
+        node.dot.accept(self)
+        node.name.accept(self)
+        node.lpar.accept(self)
+        node.args.accept(self)
+        node.rpar.accept(self)
+        self.exit_node(node)
+
+    def visit_FunctionNode(self, node: mparser.FunctionNode) -> None:
+        self.enter_node(node)
+        node.func_name.accept(self)
+        node.lpar.accept(self)
+        node.args.accept(self)
+        node.rpar.accept(self)
+        self.exit_node(node)
+
+    def visit_AssignmentNode(self, node: mparser.AssignmentNode) -> None:
+        self.enter_node(node)
+        node.var_name.accept(self)
+        node.operator.accept(self)
+        node.value.accept(self)
+        self.exit_node(node)
+
+    def visit_PlusAssignmentNode(self, node: mparser.PlusAssignmentNode) -> None:
+        self.visit_AssignmentNode(node)
+
+    def visit_ForeachClauseNode(self, node: mparser.ForeachClauseNode) -> None:
+        self.enter_node(node)
+        node.foreach_.accept(self)
+        for varname, comma in zip_longest(node.varnames, node.commas):
+            varname.accept(self)
+            if comma is not None:
+                comma.accept(self)
+        node.colon.accept(self)
+        node.items.accept(self)
+        node.block.accept(self)
+        node.endforeach.accept(self)
+        self.exit_node(node)
+
+    def visit_IfClauseNode(self, node: mparser.IfClauseNode) -> None:
+        self.enter_node(node)
+        for i in node.ifs:
+            i.accept(self)
+        node.elseblock.accept(self)
+        node.endif.accept(self)
+        self.exit_node(node)
+
+    def visit_UMinusNode(self, node: mparser.UMinusNode) -> None:
+        self.visit_UnaryOperatorNode(node)
+
+    def visit_IfNode(self, node: mparser.IfNode) -> None:
+        self.enter_node(node)
+        node.if_.accept(self)
+        node.condition.accept(self)
+        node.block.accept(self)
+        self.exit_node(node)
+
+    def visit_ElseNode(self, node: mparser.ElseNode) -> None:
+        self.enter_node(node)
+        node.else_.accept(self)
+        node.block.accept(self)
+        self.exit_node(node)
+
+    def visit_TernaryNode(self, node: mparser.TernaryNode) -> None:
+        self.enter_node(node)
+        node.condition.accept(self)
+        node.questionmark.accept(self)
+        node.trueblock.accept(self)
+        node.colon.accept(self)
+        node.falseblock.accept(self)
+        self.exit_node(node)
+
+    def visit_ArgumentNode(self, node: mparser.ArgumentNode) -> None:
+        self.enter_node(node)
+        commas_iter = iter(node.commas)
+
+        for arg in node.arguments:
+            arg.accept(self)
+            try:
+                comma = next(commas_iter)
+                comma.accept(self)
+            except StopIteration:
+                pass
+
+        assert len(node.colons) == len(node.kwargs)
+        for (key, val), colon in zip(node.kwargs.items(), node.colons):
+            key.accept(self)
+            colon.accept(self)
+            val.accept(self)
+            try:
+                comma = next(commas_iter)
+                comma.accept(self)
+            except StopIteration:
+                pass
+
+        self.exit_node(node)
+
+    def visit_ParenthesizedNode(self, node: mparser.ParenthesizedNode) -> None:
+        self.enter_node(node)
+        node.lpar.accept(self)
+        node.inner.accept(self)
+        node.rpar.accept(self)
+        self.exit_node(node)