"""

Evaluation of Python code in |jedi| is based on three assumptions:

* The code uses as least side effects as possible. Jedi understands certain

list/tuple/set modifications, but there's no guarantee that Jedi detects

everything (list.append in different modules for example).

* No magic is being used:

- metaclasses

- ``setattr()`` / ``__import__()``

- writing to ``globals()``, ``locals()``, ``object.__dict__``

* The programmer is not a total dick, e.g. like `this

<https://github.com/davidhalter/jedi/issues/24>`_ :-)

The actual algorithm is based on a principle called lazy evaluation. That

said, the typical entry point for static analysis is calling

``eval_expr_stmt``. There's separate logic for autocompletion in the API, the

evaluator is all about evaluating an expression.

TODO this paragraph is not what jedi does anymore.

Now you need to understand what follows after ``eval_expr_stmt``. Let's

make an example::

import datetime

datetime.date.toda# <-- cursor here

First of all, this module doesn't care about completion. It really just cares

about ``datetime.date``. At the end of the procedure ``eval_expr_stmt`` will

return the ``date`` class.

To *visualize* this (simplified):

- ``Evaluator.eval_expr_stmt`` doesn't do much, because there's no assignment.

- ``Context.eval_node`` cares for resolving the dotted path

- ``Evaluator.find_types`` searches for global definitions of datetime, which

it finds in the definition of an import, by scanning the syntax tree.

- Using the import logic, the datetime module is found.

- Now ``find_types`` is called again by ``eval_node`` to find ``date``

inside the datetime module.

Now what would happen if we wanted ``datetime.date.foo.bar``? Two more

calls to ``find_types``. However the second call would be ignored, because the

first one would return nothing (there's no foo attribute in ``date``).

What if the import would contain another ``ExprStmt`` like this::

from foo import bar

Date = bar.baz

Well... You get it. Just another ``eval_expr_stmt`` recursion. It's really

easy. Python can obviously get way more complicated then this. To understand

tuple assignments, list comprehensions and everything else, a lot more code had

to be written.

Jedi has been tested very well, so you can just start modifying code. It's best

to write your own test first for your "new" feature. Don't be scared of

breaking stuff. As long as the tests pass, you're most likely to be fine.

I need to mention now that lazy evaluation is really good because it

only *evaluates* what needs to be *evaluated*. All the statements and modules

that are not used are just being ignored.

"""

import sys

from parso.python import tree

import parso

from jedi import debug

from jedi import parser_utils

from jedi.evaluate.utils import unite

from jedi.evaluate import imports

from jedi.evaluate import recursion

from jedi.evaluate.cache import evaluator_function_cache

from jedi.evaluate import compiled

from jedi.evaluate import helpers

from jedi.evaluate.filters import TreeNameDefinition, ParamName

from jedi.evaluate.base_context import ContextualizedName, ContextualizedNode, \

ContextSet, NO_CONTEXTS, iterate_contexts

from jedi.evaluate.context import ClassContext, FunctionContext, \

AnonymousInstance, BoundMethod

from jedi.evaluate.context.iterable import CompForContext

from jedi.evaluate.syntax_tree import eval_trailer, eval_expr_stmt, \

eval_node, check_tuple_assignments

class Evaluator(object):

def __init__(self, grammar, project):

self.grammar = grammar

self.latest_grammar = parso.load_grammar(version='3.6')

self.memoize_cache = {} # for memoize decorators

# To memorize modules -> equals `sys.modules`.

self.modules = {} # like `sys.modules`.

self.compiled_cache = {} # see `evaluate.compiled.create()`

self.inferred_element_counts = {}

self.mixed_cache = {} # see `evaluate.compiled.mixed._create()`

self.analysis = []

self.dynamic_params_depth = 0

self.is_analysis = False

self.python_version = sys.version_info[:2]

self.project = project

project.add_evaluator(self)

self.reset_recursion_limitations()

# Constants

self.BUILTINS = compiled.get_special_object(self, 'BUILTINS')

def reset_recursion_limitations(self):

self.recursion_detector = recursion.RecursionDetector()

self.execution_recursion_detector = recursion.ExecutionRecursionDetector(self)

def eval_element(self, context, element):

if isinstance(context, CompForContext):

return eval_node(context, element)

if_stmt = element

while if_stmt is not None:

if_stmt = if_stmt.parent

if if_stmt.type in ('if_stmt', 'for_stmt'):

break

if parser_utils.is_scope(if_stmt):

if_stmt = None

break

predefined_if_name_dict = context.predefined_names.get(if_stmt)

if predefined_if_name_dict is None and if_stmt and if_stmt.type == 'if_stmt':

if_stmt_test = if_stmt.children[1]

name_dicts = [{}]

# If we already did a check, we don't want to do it again -> If

# context.predefined_names is filled, we stop.

# We don't want to check the if stmt itself, it's just about

# the content.

if element.start_pos > if_stmt_test.end_pos:

# Now we need to check if the names in the if_stmt match the

# names in the suite.

if_names = helpers.get_names_of_node(if_stmt_test)

element_names = helpers.get_names_of_node(element)

str_element_names = [e.value for e in element_names]

if any(i.value in str_element_names for i in if_names):

for if_name in if_names:

definitions = self.goto_definitions(context, if_name)

# Every name that has multiple different definitions

# causes the complexity to rise. The complexity should

# never fall below 1.

if len(definitions) > 1:

if len(name_dicts) * len(definitions) > 16:

debug.dbg('Too many options for if branch evaluation %s.', if_stmt)

# There's only a certain amount of branches

# Jedi can evaluate, otherwise it will take to

# long.

name_dicts = [{}]

break

original_name_dicts = list(name_dicts)

name_dicts = []

for definition in definitions:

new_name_dicts = list(original_name_dicts)

for i, name_dict in enumerate(new_name_dicts):

new_name_dicts[i] = name_dict.copy()

new_name_dicts[i][if_name.value] = ContextSet(definition)

name_dicts += new_name_dicts

else:

for name_dict in name_dicts:

name_dict[if_name.value] = definitions

if len(name_dicts) > 1:

result = ContextSet()

for name_dict in name_dicts:

with helpers.predefine_names(context, if_stmt, name_dict):

result |= eval_node(context, element)

return result

else:

return self._eval_element_if_evaluated(context, element)

else:

if predefined_if_name_dict:

return eval_node(context, element)

else:

return self._eval_element_if_evaluated(context, element)

def _eval_element_if_evaluated(self, context, element):

"""

TODO This function is temporary: Merge with eval_element.

"""

parent = element

while parent is not None:

parent = parent.parent

predefined_if_name_dict = context.predefined_names.get(parent)

if predefined_if_name_dict is not None:

return eval_node(context, element)

return self._eval_element_cached(context, element)

@evaluator_function_cache(default=NO_CONTEXTS)

def _eval_element_cached(self, context, element):

return eval_node(context, element)

def goto_definitions(self, context, name):

def_ = name.get_definition(import_name_always=True)

if def_ is not None:

type_ = def_.type

if type_ == 'classdef':

return [ClassContext(self, context, name.parent)]

elif type_ == 'funcdef':

return [FunctionContext(self, context, name.parent)]

if type_ == 'expr_stmt':

is_simple_name = name.parent.type not in ('power', 'trailer')

if is_simple_name:

return eval_expr_stmt(context, def_, name)

if type_ == 'for_stmt':

container_types = context.eval_node(def_.children[3])

cn = ContextualizedNode(context, def_.children[3])

for_types = iterate_contexts(container_types, cn)

c_node = ContextualizedName(context, name)

return check_tuple_assignments(self, c_node, for_types)

if type_ in ('import_from', 'import_name'):

return imports.infer_import(context, name)

return helpers.evaluate_call_of_leaf(context, name)

def goto(self, context, name):

definition = name.get_definition(import_name_always=True)

if definition is not None:

type_ = definition.type

if type_ == 'expr_stmt':

# Only take the parent, because if it's more complicated than just

# a name it's something you can "goto" again.

is_simple_name = name.parent.type not in ('power', 'trailer')

if is_simple_name:

return [TreeNameDefinition(context, name)]

elif type_ == 'param':

return [ParamName(context, name)]

elif type_ in ('funcdef', 'classdef'):

return [TreeNameDefinition(context, name)]

elif type_ in ('import_from', 'import_name'):

module_names = imports.infer_import(context, name, is_goto=True)

return module_names

par = name.parent

node_type = par.type

if node_type == 'argument' and par.children[1] == '=' and par.children[0] == name:

# Named param goto.

trailer = par.parent

if trailer.type == 'arglist':

trailer = trailer.parent

if trailer.type != 'classdef':

if trailer.type == 'decorator':

context_set = context.eval_node(trailer.children[1])

else:

i = trailer.parent.children.index(trailer)

to_evaluate = trailer.parent.children[:i]

if to_evaluate[0] == 'await':

to_evaluate.pop(0)

context_set = context.eval_node(to_evaluate[0])

for trailer in to_evaluate[1:]:

context_set = eval_trailer(context, context_set, trailer)

param_names = []

for context in context_set:

try:

get_param_names = context.get_param_names

except AttributeError:

pass

else:

for param_name in get_param_names():

if param_name.string_name == name.value:

param_names.append(param_name)

return param_names

elif node_type == 'dotted_name': # Is a decorator.

index = par.children.index(name)

if index > 0:

new_dotted = helpers.deep_ast_copy(par)

new_dotted.children[index - 1:] = []

values = context.eval_node(new_dotted)

return unite(

value.py__getattribute__(name, name_context=context, is_goto=True)

for value in values

)

if node_type == 'trailer' and par.children[0] == '.':

values = helpers.evaluate_call_of_leaf(context, name, cut_own_trailer=True)

return unite(

value.py__getattribute__(name, name_context=context, is_goto=True)

for value in values

)

else:

stmt = tree.search_ancestor(

name, 'expr_stmt', 'lambdef'

) or name

if stmt.type == 'lambdef':

stmt = name

return context.py__getattribute__(

name,

position=stmt.start_pos,

search_global=True, is_goto=True

)

def create_context(self, base_context, node, node_is_context=False, node_is_object=False):

def parent_scope(node):

while True:

node = node.parent

if parser_utils.is_scope(node):

return node

elif node.type in ('argument', 'testlist_comp'):

if node.children[1].type == 'comp_for':

return node.children[1]

elif node.type == 'dictorsetmaker':

for n in node.children[1:4]:

# In dictionaries it can be pretty much anything.

if n.type == 'comp_for':

return n

def from_scope_node(scope_node, child_is_funcdef=None, is_nested=True, node_is_object=False):

if scope_node == base_node:

return base_context

is_funcdef = scope_node.type in ('funcdef', 'lambdef')

parent_scope = parser_utils.get_parent_scope(scope_node)

parent_context = from_scope_node(parent_scope, child_is_funcdef=is_funcdef)

if is_funcdef:

if isinstance(parent_context, AnonymousInstance):

func = BoundMethod(

self, parent_context, parent_context.class_context,

parent_context.parent_context, scope_node

)

else:

func = FunctionContext(

self,

parent_context,

scope_node

)

if is_nested and not node_is_object:

return func.get_function_execution()

return func

elif scope_node.type == 'classdef':

class_context = ClassContext(self, parent_context, scope_node)

if child_is_funcdef:

# anonymous instance

return AnonymousInstance(self, parent_context, class_context)

else:

return class_context

elif scope_node.type == 'comp_for':

if node.start_pos >= scope_node.children[-1].start_pos:

return parent_context

return CompForContext.from_comp_for(parent_context, scope_node)

raise Exception("There's a scope that was not managed.")

base_node = base_context.tree_node

if node_is_context and parser_utils.is_scope(node):

scope_node = node

else:

if node.parent.type in ('funcdef', 'classdef') and node.parent.name == node:

# When we're on class/function names/leafs that define the

# object itself and not its contents.

node = node.parent

scope_node = parent_scope(node)

return from_scope_node(scope_node, is_nested=True, node_is_object=node_is_object)