Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/jinja2/optimizer.py: 42%

1"""The optimizer tries to constant fold expressions and modify the AST 

2in place so that it should be faster to evaluate. 

3 

4Because the AST does not contain all the scoping information and the 

5compiler has to find that out, we cannot do all the optimizations we 

6want. For example, loop unrolling doesn't work because unrolled loops 

7would have a different scope. The solution would be a second syntax tree 

8that stored the scoping rules. 

9""" 

10 

11import typing as t 

12 

13from . import nodes 

14from .visitor import NodeTransformer 

15 

16if t.TYPE_CHECKING: 

17 from .environment import Environment 

18 

19 

20def optimize(node: nodes.Node, environment: "Environment") -> nodes.Node: 

21 """The context hint can be used to perform an static optimization 

22 based on the context given.""" 

23 optimizer = Optimizer(environment) 

24 return t.cast(nodes.Node, optimizer.visit(node)) 

25 

26 

27class Optimizer(NodeTransformer): 

28 def __init__(self, environment: "t.Optional[Environment]") -> None: 

29 self.environment = environment 

30 

31 def generic_visit( 

32 self, node: nodes.Node, *args: t.Any, **kwargs: t.Any 

33 ) -> nodes.Node: 

34 node = super().generic_visit(node, *args, **kwargs) 

35 

36 # Do constant folding. Some other nodes besides Expr have 

37 # as_const, but folding them causes errors later on. 

38 if isinstance(node, nodes.Expr): 

39 try: 

40 return nodes.Const.from_untrusted( 

41 node.as_const(args[0] if args else None), 

42 lineno=node.lineno, 

43 environment=self.environment, 

44 ) 

45 except nodes.Impossible: 

46 pass 

47 

48 return node