• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1import typing as t
2
3from . import nodes
4from .visitor import NodeVisitor
5
6VAR_LOAD_PARAMETER = "param"
7VAR_LOAD_RESOLVE = "resolve"
8VAR_LOAD_ALIAS = "alias"
9VAR_LOAD_UNDEFINED = "undefined"
10
11
12def find_symbols(
13    nodes: t.Iterable[nodes.Node], parent_symbols: t.Optional["Symbols"] = None
14) -> "Symbols":
15    sym = Symbols(parent=parent_symbols)
16    visitor = FrameSymbolVisitor(sym)
17    for node in nodes:
18        visitor.visit(node)
19    return sym
20
21
22def symbols_for_node(
23    node: nodes.Node, parent_symbols: t.Optional["Symbols"] = None
24) -> "Symbols":
25    sym = Symbols(parent=parent_symbols)
26    sym.analyze_node(node)
27    return sym
28
29
30class Symbols:
31    def __init__(
32        self, parent: t.Optional["Symbols"] = None, level: t.Optional[int] = None
33    ) -> None:
34        if level is None:
35            if parent is None:
36                level = 0
37            else:
38                level = parent.level + 1
39
40        self.level: int = level
41        self.parent = parent
42        self.refs: t.Dict[str, str] = {}
43        self.loads: t.Dict[str, t.Any] = {}
44        self.stores: t.Set[str] = set()
45
46    def analyze_node(self, node: nodes.Node, **kwargs: t.Any) -> None:
47        visitor = RootVisitor(self)
48        visitor.visit(node, **kwargs)
49
50    def _define_ref(
51        self, name: str, load: t.Optional[t.Tuple[str, t.Optional[str]]] = None
52    ) -> str:
53        ident = f"l_{self.level}_{name}"
54        self.refs[name] = ident
55        if load is not None:
56            self.loads[ident] = load
57        return ident
58
59    def find_load(self, target: str) -> t.Optional[t.Any]:
60        if target in self.loads:
61            return self.loads[target]
62
63        if self.parent is not None:
64            return self.parent.find_load(target)
65
66        return None
67
68    def find_ref(self, name: str) -> t.Optional[str]:
69        if name in self.refs:
70            return self.refs[name]
71
72        if self.parent is not None:
73            return self.parent.find_ref(name)
74
75        return None
76
77    def ref(self, name: str) -> str:
78        rv = self.find_ref(name)
79        if rv is None:
80            raise AssertionError(
81                "Tried to resolve a name to a reference that was"
82                f" unknown to the frame ({name!r})"
83            )
84        return rv
85
86    def copy(self) -> "Symbols":
87        rv = object.__new__(self.__class__)
88        rv.__dict__.update(self.__dict__)
89        rv.refs = self.refs.copy()
90        rv.loads = self.loads.copy()
91        rv.stores = self.stores.copy()
92        return rv
93
94    def store(self, name: str) -> None:
95        self.stores.add(name)
96
97        # If we have not see the name referenced yet, we need to figure
98        # out what to set it to.
99        if name not in self.refs:
100            # If there is a parent scope we check if the name has a
101            # reference there.  If it does it means we might have to alias
102            # to a variable there.
103            if self.parent is not None:
104                outer_ref = self.parent.find_ref(name)
105                if outer_ref is not None:
106                    self._define_ref(name, load=(VAR_LOAD_ALIAS, outer_ref))
107                    return
108
109            # Otherwise we can just set it to undefined.
110            self._define_ref(name, load=(VAR_LOAD_UNDEFINED, None))
111
112    def declare_parameter(self, name: str) -> str:
113        self.stores.add(name)
114        return self._define_ref(name, load=(VAR_LOAD_PARAMETER, None))
115
116    def load(self, name: str) -> None:
117        if self.find_ref(name) is None:
118            self._define_ref(name, load=(VAR_LOAD_RESOLVE, name))
119
120    def branch_update(self, branch_symbols: t.Sequence["Symbols"]) -> None:
121        stores: t.Dict[str, int] = {}
122        for branch in branch_symbols:
123            for target in branch.stores:
124                if target in self.stores:
125                    continue
126                stores[target] = stores.get(target, 0) + 1
127
128        for sym in branch_symbols:
129            self.refs.update(sym.refs)
130            self.loads.update(sym.loads)
131            self.stores.update(sym.stores)
132
133        for name, branch_count in stores.items():
134            if branch_count == len(branch_symbols):
135                continue
136
137            target = self.find_ref(name)  # type: ignore
138            assert target is not None, "should not happen"
139
140            if self.parent is not None:
141                outer_target = self.parent.find_ref(name)
142                if outer_target is not None:
143                    self.loads[target] = (VAR_LOAD_ALIAS, outer_target)
144                    continue
145            self.loads[target] = (VAR_LOAD_RESOLVE, name)
146
147    def dump_stores(self) -> t.Dict[str, str]:
148        rv: t.Dict[str, str] = {}
149        node: t.Optional["Symbols"] = self
150
151        while node is not None:
152            for name in sorted(node.stores):
153                if name not in rv:
154                    rv[name] = self.find_ref(name)  # type: ignore
155
156            node = node.parent
157
158        return rv
159
160    def dump_param_targets(self) -> t.Set[str]:
161        rv = set()
162        node: t.Optional["Symbols"] = self
163
164        while node is not None:
165            for target, (instr, _) in self.loads.items():
166                if instr == VAR_LOAD_PARAMETER:
167                    rv.add(target)
168
169            node = node.parent
170
171        return rv
172
173
174class RootVisitor(NodeVisitor):
175    def __init__(self, symbols: "Symbols") -> None:
176        self.sym_visitor = FrameSymbolVisitor(symbols)
177
178    def _simple_visit(self, node: nodes.Node, **kwargs: t.Any) -> None:
179        for child in node.iter_child_nodes():
180            self.sym_visitor.visit(child)
181
182    visit_Template = _simple_visit
183    visit_Block = _simple_visit
184    visit_Macro = _simple_visit
185    visit_FilterBlock = _simple_visit
186    visit_Scope = _simple_visit
187    visit_If = _simple_visit
188    visit_ScopedEvalContextModifier = _simple_visit
189
190    def visit_AssignBlock(self, node: nodes.AssignBlock, **kwargs: t.Any) -> None:
191        for child in node.body:
192            self.sym_visitor.visit(child)
193
194    def visit_CallBlock(self, node: nodes.CallBlock, **kwargs: t.Any) -> None:
195        for child in node.iter_child_nodes(exclude=("call",)):
196            self.sym_visitor.visit(child)
197
198    def visit_OverlayScope(self, node: nodes.OverlayScope, **kwargs: t.Any) -> None:
199        for child in node.body:
200            self.sym_visitor.visit(child)
201
202    def visit_For(
203        self, node: nodes.For, for_branch: str = "body", **kwargs: t.Any
204    ) -> None:
205        if for_branch == "body":
206            self.sym_visitor.visit(node.target, store_as_param=True)
207            branch = node.body
208        elif for_branch == "else":
209            branch = node.else_
210        elif for_branch == "test":
211            self.sym_visitor.visit(node.target, store_as_param=True)
212            if node.test is not None:
213                self.sym_visitor.visit(node.test)
214            return
215        else:
216            raise RuntimeError("Unknown for branch")
217
218        if branch:
219            for item in branch:
220                self.sym_visitor.visit(item)
221
222    def visit_With(self, node: nodes.With, **kwargs: t.Any) -> None:
223        for target in node.targets:
224            self.sym_visitor.visit(target)
225        for child in node.body:
226            self.sym_visitor.visit(child)
227
228    def generic_visit(self, node: nodes.Node, *args: t.Any, **kwargs: t.Any) -> None:
229        raise NotImplementedError(f"Cannot find symbols for {type(node).__name__!r}")
230
231
232class FrameSymbolVisitor(NodeVisitor):
233    """A visitor for `Frame.inspect`."""
234
235    def __init__(self, symbols: "Symbols") -> None:
236        self.symbols = symbols
237
238    def visit_Name(
239        self, node: nodes.Name, store_as_param: bool = False, **kwargs: t.Any
240    ) -> None:
241        """All assignments to names go through this function."""
242        if store_as_param or node.ctx == "param":
243            self.symbols.declare_parameter(node.name)
244        elif node.ctx == "store":
245            self.symbols.store(node.name)
246        elif node.ctx == "load":
247            self.symbols.load(node.name)
248
249    def visit_NSRef(self, node: nodes.NSRef, **kwargs: t.Any) -> None:
250        self.symbols.load(node.name)
251
252    def visit_If(self, node: nodes.If, **kwargs: t.Any) -> None:
253        self.visit(node.test, **kwargs)
254        original_symbols = self.symbols
255
256        def inner_visit(nodes: t.Iterable[nodes.Node]) -> "Symbols":
257            self.symbols = rv = original_symbols.copy()
258
259            for subnode in nodes:
260                self.visit(subnode, **kwargs)
261
262            self.symbols = original_symbols
263            return rv
264
265        body_symbols = inner_visit(node.body)
266        elif_symbols = inner_visit(node.elif_)
267        else_symbols = inner_visit(node.else_ or ())
268        self.symbols.branch_update([body_symbols, elif_symbols, else_symbols])
269
270    def visit_Macro(self, node: nodes.Macro, **kwargs: t.Any) -> None:
271        self.symbols.store(node.name)
272
273    def visit_Import(self, node: nodes.Import, **kwargs: t.Any) -> None:
274        self.generic_visit(node, **kwargs)
275        self.symbols.store(node.target)
276
277    def visit_FromImport(self, node: nodes.FromImport, **kwargs: t.Any) -> None:
278        self.generic_visit(node, **kwargs)
279
280        for name in node.names:
281            if isinstance(name, tuple):
282                self.symbols.store(name[1])
283            else:
284                self.symbols.store(name)
285
286    def visit_Assign(self, node: nodes.Assign, **kwargs: t.Any) -> None:
287        """Visit assignments in the correct order."""
288        self.visit(node.node, **kwargs)
289        self.visit(node.target, **kwargs)
290
291    def visit_For(self, node: nodes.For, **kwargs: t.Any) -> None:
292        """Visiting stops at for blocks.  However the block sequence
293        is visited as part of the outer scope.
294        """
295        self.visit(node.iter, **kwargs)
296
297    def visit_CallBlock(self, node: nodes.CallBlock, **kwargs: t.Any) -> None:
298        self.visit(node.call, **kwargs)
299
300    def visit_FilterBlock(self, node: nodes.FilterBlock, **kwargs: t.Any) -> None:
301        self.visit(node.filter, **kwargs)
302
303    def visit_With(self, node: nodes.With, **kwargs: t.Any) -> None:
304        for target in node.values:
305            self.visit(target)
306
307    def visit_AssignBlock(self, node: nodes.AssignBlock, **kwargs: t.Any) -> None:
308        """Stop visiting at block assigns."""
309        self.visit(node.target, **kwargs)
310
311    def visit_Scope(self, node: nodes.Scope, **kwargs: t.Any) -> None:
312        """Stop visiting at scopes."""
313
314    def visit_Block(self, node: nodes.Block, **kwargs: t.Any) -> None:
315        """Stop visiting at blocks."""
316
317    def visit_OverlayScope(self, node: nodes.OverlayScope, **kwargs: t.Any) -> None:
318        """Do not visit into overlay scopes."""
319