Add a get_additional_deps hook to Plugin to support django-stubs (#6598)

django-stubs needs to be able to add in additional dependencies to
modules and is currently using monkeypatching to do it.

That is 1) not great and 2) breaks under mypyc.
Add a hook to support generating additional dependencies from a plugin.

mypy/build.py

@@ -1967,7 +1967,9 @@ def compute_dependencies(self) -> None:
         dependencies = []
         priorities = {}  # type: Dict[str, int]  # id -> priority
         dep_line_map = {}  # type: Dict[str, int]  # id -> line
-        for pri, id, line in manager.all_imported_modules_in_file(self.tree):
+        dep_entries = (manager.all_imported_modules_in_file(self.tree) +
+                       self.manager.plugin.get_additional_deps(self.tree))
+        for pri, id, line in dep_entries:
             priorities[id] = min(pri, priorities.get(id, PRI_ALL))
             if id == self.id:
                 continue

mypy/interpreted_plugin.py

@@ -1,6 +1,6 @@
 """Hack for handling non-mypyc compiled plugins with a mypyc-compiled mypy"""
 
-from typing import Optional, Callable, Any, Dict
+from typing import Optional, Callable, Any, Dict, List, Tuple
 from mypy.options import Options
 from mypy.types import Type, CallableType
 from mypy.nodes import SymbolTableNode, MypyFile
@@ -39,6 +39,9 @@ def lookup_fully_qualified(self, fullname: str) -> Optional[SymbolTableNode]:
         assert self._modules is not None
         return lookup_fully_qualified(fullname, self._modules)
 
+    def get_additional_deps(self, file: MypyFile) -> List[Tuple[int, str, int]]:
+        return []
+
     def get_type_analyze_hook(self, fullname: str
                               ) -> Optional[Callable[['mypy.plugin.AnalyzeTypeContext'], Type]]:
         return None

mypy/plugin.py

@@ -371,6 +371,23 @@ def lookup_fully_qualified(self, fullname: str) -> Optional[SymbolTableNode]:
         assert self._modules is not None
         return lookup_fully_qualified(fullname, self._modules)
 
+    def get_additional_deps(self, file: MypyFile) -> List[Tuple[int, str, int]]:
+        """Customize dependencies for a module.
+
+        This hook allows adding in new dependencies for a module. It
+        is called after parsing a file but before analysis. This can
+        be useful if a library has dependencies that are dynamic based
+        on configuration information, for example.
+
+        Returns a list of (priority, module name, line number) tuples.
+
+        The line number can be -1 when there is not a known real line number.
+
+        Priorities are defined in mypy.build (but maybe shouldn't be).
+        10 is a good choice for priority.
+        """
+        return []
+
     def get_type_analyze_hook(self, fullname: str
                               ) -> Optional[Callable[[AnalyzeTypeContext], Type]]:
         """Customize behaviour of the type analyzer for given full names.
@@ -395,7 +412,7 @@ def get_function_hook(self, fullname: str
         """Adjust the return type of a function call.
 
         This method is called after type checking a call. Plugin may adjust the return
-        type inferred by mypy, and/or emmit some error messages. Note, this hook is also
+        type inferred by mypy, and/or emit some error messages. Note, this hook is also
         called for class instantiation calls, so that in this example:
 
             from lib import Class, do_stuff
@@ -561,6 +578,9 @@ def set_modules(self, modules: Dict[str, MypyFile]) -> None:
     def lookup_fully_qualified(self, fullname: str) -> Optional[SymbolTableNode]:
         return self.plugin.lookup_fully_qualified(fullname)
 
+    def get_additional_deps(self, file: MypyFile) -> List[Tuple[int, str, int]]:
+        return self.plugin.get_additional_deps(file)
+
     def get_type_analyze_hook(self, fullname: str
                               ) -> Optional[Callable[[AnalyzeTypeContext], Type]]:
         return self.plugin.get_type_analyze_hook(fullname)
@@ -626,6 +646,12 @@ def set_modules(self, modules: Dict[str, MypyFile]) -> None:
         for plugin in self._plugins:
             plugin.set_modules(modules)
 
+    def get_additional_deps(self, file: MypyFile) -> List[Tuple[int, str, int]]:
+        deps = []
+        for plugin in self._plugins:
+            deps.extend(plugin.get_additional_deps(file))
+        return deps
+
     def get_type_analyze_hook(self, fullname: str
                               ) -> Optional[Callable[[AnalyzeTypeContext], Type]]:
         return self._find_hook(lambda plugin: plugin.get_type_analyze_hook(fullname))

test-data/unit/check-custom-plugin.test

@@ -71,7 +71,6 @@ tmp/mypy.ini:2: error: Can't find plugin 'tmp/missing.py'
 plugins=missing
 [out]
 tmp/mypy.ini:2: error: Error importing plugin 'missing'
---' (work around syntax highlighting)
 
 [case testMultipleSectionsDefinePlugin]
 # flags: --config-file tmp/mypy.ini
@@ -585,3 +584,16 @@ reveal_type(instance(2))  # E: Revealed type is 'builtins.float*'
 [file mypy.ini]
 [[mypy]
 plugins=<ROOT>/test-data/unit/plugins/callable_instance.py
+
+[case testPluginDependencies]
+# flags: --config-file tmp/mypy.ini
+
+# The top level file here doesn't do anything, but the plugin should add
+# a dependency on err that will cause err to be processed and an error reported.
+
+[file err.py]
+1 + 'lol'  # E: Unsupported operand types for + ("int" and "str")
+
+[file mypy.ini]
+[[mypy]
+plugins=<ROOT>/test-data/unit/plugins/depshook.py

test-data/unit/plugins/depshook.py

@@ -0,0 +1,15 @@
+from typing import Optional, Callable, List, Tuple
+
+from mypy.plugin import Plugin
+from mypy.nodes import MypyFile
+
+
+class DepsPlugin(Plugin):
+    def get_additional_deps(self, file: MypyFile) -> List[Tuple[int, str, int]]:
+        if file.fullname() == '__main__':
+            return [(10, 'err', -1)]
+        return []
+
+
+def plugin(version):
+    return DepsPlugin