Class SemanticAnalyzerPreAnalysis

mypy/semanal_pass1.py:30–159

Analyze reachability of blocks and imports and other local things. This runs before semantic analysis, so names have not been bound. Imports are also not resolved yet, so we can only access the current module. This determines static reachability of blocks and imports due to version and

class SemanticAnalyzerPreAnalysis(TraverserVisitor):
    """Analyze reachability of blocks and imports and other local things.

    This runs before semantic analysis, so names have not been bound. Imports are
    also not resolved yet, so we can only access the current module.

    This determines static reachability of blocks and imports due to version and
    platform checks, among others.

    The main entry point is 'visit_file'.

    Reachability of imports needs to be determined very early in the build since
    this affects which modules will ultimately be processed.

    Consider this example:

      import sys

      def do_stuff() -> None:
          if sys.version_info >= (3, 11):
              import xyz  # Only available in Python 3.11+
              xyz.whatever()
          ...

    The block containing 'import xyz' is unreachable in Python 3.10 mode. The import
    shouldn't be processed in Python 3.10 mode, even if the module happens to exist.
    """

    def visit_file(self, file: MypyFile, fnam: str, mod_id: str, options: Options) -> None:
        self.platform = options.platform
        self.cur_mod_id = mod_id
        self.cur_mod_node = file
        self.options = options
        self.is_global_scope = True
        self.skipped_lines: set[int] = set()

        for i, defn in enumerate(file.defs):
            defn.accept(self)
            if isinstance(defn, AssertStmt) and assert_will_always_fail(defn, options):
                # We've encountered an assert that's always false,
                # e.g. assert sys.platform == 'lol'.  Truncate the
                # list of statements.  This mutates file.defs too.
                if i < len(file.defs) - 1:
                    next_def, last = file.defs[i + 1], file.defs[-1]
                    if last.end_line is not None:
                        # We are on a Python version recent enough to support end lines.
                        self.skipped_lines |= set(range(next_def.line, last.end_line + 1))
                file.imports = [
                    i for i in file.imports if (i.line, i.column) <= (defn.line, defn.column)
                ]
                del file.defs[i + 1 :]
                break
        file.skipped_lines = self.skipped_lines

    def visit_func_def(self, node: FuncDef) -> None:
        old_global_scope = self.is_global_scope
        self.is_global_scope = False
        super().visit_func_def(node)