[gtk-doc/wip/smcv/internal-tree] Implement a simple tree structure without using anytree

[Simon McVittie <smcv src gnome org>]

commit 9e289cd74056c42ac6ea824809efcb65bd265a85
Author: Simon McVittie <smcv debian org>
Date:   Thu Aug 22 09:31:19 2019 +0100

    Implement a simple tree structure without using anytree
    
    anytree isn't currently available in Debian or Ubuntu, and seems like
    a lot of code just to get a tree data structure. Reimplement just the
    bits we need, with a compatible API.
    
    Signed-off-by: Simon McVittie <smcv debian org>

 gtkdoc/mkhtml2.py | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 tests/mkhtml2.py  |  2 +-
 2 files changed, 52 insertions(+), 2 deletions(-)
---
diff --git a/gtkdoc/mkhtml2.py b/gtkdoc/mkhtml2.py
index 2eb5c73..093deb3 100644
--- a/gtkdoc/mkhtml2.py
+++ b/gtkdoc/mkhtml2.py
@@ -101,7 +101,6 @@ import os
 import shutil
 import sys
 
-from anytree import Node, PreOrderIter
 from copy import deepcopy
 from glob import glob
 from lxml import etree
@@ -254,6 +253,57 @@ def get_chunk_titles(module, node, tree_node):
     return result
 
 
+class PreOrderIter:
+    def __init__(self, node):
+        self.__node = node
+
+    def __iter__(self):
+        yield self.__node
+
+        for child in self.__node.descendants:
+            yield child
+
+
+class Node:
+    def __init__(self, name, parent=None, **kwargs):
+        self.name = name
+        self.__root = None
+        self.__attrs = kwargs
+        self.children = []
+
+        assert parent is None or isinstance(parent, Node)
+        self.parent = parent
+        if parent is not None:
+            self.__root = parent.root
+            parent.children.append(self)
+
+    @property
+    def root(self):
+        return self.__root or self
+
+    @property
+    def descendants(self):
+        ret = []
+
+        for child in self.children:
+            ret.append(child)
+
+            for other in child.descendants:
+                ret.append(other)
+
+        return ret
+
+    def __iter__(self):
+        for child in self.children:
+            yield child
+
+    def __getattr__(self, name):
+        try:
+            return self.__attrs[name]
+        except KeyError as e:
+            raise AttributeError(str(e))
+
+
 def chunk(xml_node, module, depth=0, idx=0, parent=None):
     """Chunk the tree.
 
diff --git a/tests/mkhtml2.py b/tests/mkhtml2.py
index c61ee27..439e7fe 100755
--- a/tests/mkhtml2.py
+++ b/tests/mkhtml2.py
@@ -22,11 +22,11 @@ import logging
 import textwrap
 import unittest
 
-from anytree import PreOrderIter
 from lxml import etree
 from parameterized import parameterized
 
 from gtkdoc import mkhtml2
+from gtkdoc.mkhtml2 import PreOrderIter
 
 
 class TestChunking(unittest.TestCase):