Save information about old values of values

powerline/lint/markedjson/error.py

@@ -42,15 +42,16 @@ def strtrans(s):
 
 
 class Mark:
-	def __init__(self, name, line, column, buffer, pointer):
+	def __init__(self, name, line, column, buffer, pointer, old_mark=None):
 		self.name = name
 		self.line = line
 		self.column = column
 		self.buffer = buffer
 		self.pointer = pointer
+		self.old_mark = old_mark
 
 	def copy(self):
-		return Mark(self.name, self.line, self.column, self.buffer, self.pointer)
+		return Mark(self.name, self.line, self.column, self.buffer, self.pointer, self.old_mark)
 
 	def get_snippet(self, indent=4, max_length=75):
 		if self.buffer is None:
@@ -85,17 +86,46 @@ class Mark:
 		ret.pointer += diff
 		return ret
 
-	def __str__(self):
-		snippet = self.get_snippet()
-		where = ('  in "%s", line %d, column %d' % (
-			self.name, self.line + 1, self.column + 1))
-		if snippet is not None:
-			where += ':\n' + snippet
+	def set_old_mark(self, old_mark):
+		if self is old_mark:
+			return
+		checked_marks = set([id(self)])
+		older_mark = old_mark
+		while True:
+			if id(older_mark) in checked_marks:
+				raise ValueError('Trying to set recursive marks')
+			checked_marks.add(id(older_mark))
+			older_mark = older_mark.old_mark
+			if not older_mark:
+				break
+		self.old_mark = old_mark
+
+	def to_string(self, indent=0):
+		mark = self
+		where = ''
+		processed_marks = set()
+		while mark:
+			indentstr = ' ' * indent
+			snippet = mark.get_snippet(indent=(indent + 4))
+			where += (indentstr + '  in "%s", line %d, column %d' % (
+				mark.name, mark.line + 1, mark.column + 1))
+			if snippet:
+				where += ':\n' + snippet
+			processed_marks.add(id(mark))
+			if mark.old_mark:
+				where += '\n' + indentstr + '  which replaced value\n'
+				indent += 4
+			mark = mark.old_mark
+			if id(mark) in processed_marks:
+				raise ValueError('Trying to dump recursive mark')
 		if type(where) is str:
 			return where
 		else:
 			return where.encode('utf-8')
 
+	def __str__(self):
+		return self.to_string()
+
 
 def echoerr(*args, **kwargs):
 	stream = kwargs.pop('stream', sys.stderr)

powerline/lint/markedjson/markedvalue.py

@@ -66,6 +66,21 @@ class MarkedDict(dict):
 		return r
 
 	def __setitem__(self, key, value):
+		try:
+			old_value = self[key]
+		except KeyError:
+			pass
+		else:
+			try:
+				key.mark.set_old_mark(self.keydict[key].mark)
+			except AttributeError:
+				pass
+			except KeyError:
+				pass
+			try:
+				value.mark.set_old_mark(old_value.mark)
+			except AttributeError:
+				pass
 		dict.__setitem__(self, key, value)
 		self.keydict[key] = key