Refactor Jupyter magic handling (#2545)

src/black/handle_ipynb_magics.py

@@ -39,18 +39,18 @@
 )
 NON_PYTHON_CELL_MAGICS = frozenset(
     (
-        "%%bash",
-        "%%html",
-        "%%javascript",
-        "%%js",
-        "%%latex",
-        "%%markdown",
-        "%%perl",
-        "%%ruby",
-        "%%script",
-        "%%sh",
-        "%%svg",
-        "%%writefile",
+        "bash",
+        "html",
+        "javascript",
+        "js",
+        "latex",
+        "markdown",
+        "perl",
+        "ruby",
+        "script",
+        "sh",
+        "svg",
+        "writefile",
     )
 )
 TOKEN_HEX = secrets.token_hex
@@ -230,10 +230,11 @@ def replace_cell_magics(src: str) -> Tuple[str, List[Replacement]]:
     cell_magic_finder.visit(tree)
     if cell_magic_finder.cell_magic is None:
         return src, replacements
-    if cell_magic_finder.cell_magic.header.split()[0] in NON_PYTHON_CELL_MAGICS:
+    if cell_magic_finder.cell_magic.name in NON_PYTHON_CELL_MAGICS:
         raise NothingChanged
-    mask = get_token(src, cell_magic_finder.cell_magic.header)
-    replacements.append(Replacement(mask=mask, src=cell_magic_finder.cell_magic.header))
+    header = cell_magic_finder.cell_magic.header
+    mask = get_token(src, header)
+    replacements.append(Replacement(mask=mask, src=header))
     return f"{mask}\n{cell_magic_finder.cell_magic.body}", replacements
 
 
@@ -311,11 +312,26 @@ def _is_ipython_magic(node: ast.expr) -> TypeGuard[ast.Attribute]:
     )
 
 
+def _get_str_args(args: List[ast.expr]) -> List[str]:
+    str_args = []
+    for arg in args:
+        assert isinstance(arg, ast.Str)
+        str_args.append(arg.s)
+    return str_args
+
+
 @dataclasses.dataclass(frozen=True)
 class CellMagic:
-    header: str
+    name: str
+    params: Optional[str]
     body: str
 
+    @property
+    def header(self) -> str:
+        if self.params:
+            return f"%%{self.name} {self.params}"
+        return f"%%{self.name}"
+
 
 @dataclasses.dataclass
 class CellMagicFinder(ast.NodeVisitor):
@@ -345,14 +361,8 @@ def visit_Expr(self, node: ast.Expr) -> None:
             and _is_ipython_magic(node.value.func)
             and node.value.func.attr == "run_cell_magic"
         ):
-            args = []
-            for arg in node.value.args:
-                assert isinstance(arg, ast.Str)
-                args.append(arg.s)
-            header = f"%%{args[0]}"
-            if args[1]:
-                header += f" {args[1]}"
-            self.cell_magic = CellMagic(header=header, body=args[2])
+            args = _get_str_args(node.value.args)
+            self.cell_magic = CellMagic(name=args[0], params=args[1], body=args[2])
         self.generic_visit(node)
 
 
@@ -404,12 +414,8 @@ def visit_Assign(self, node: ast.Assign) -> None:
             and _is_ipython_magic(node.value.func)
             and node.value.func.attr == "getoutput"
         ):
-            args = []
-            for arg in node.value.args:
-                assert isinstance(arg, ast.Str)
-                args.append(arg.s)
-            assert args
-            src = f"!{args[0]}"
+            (arg,) = _get_str_args(node.value.args)
+            src = f"!{arg}"
             self.magics[node.value.lineno].append(
                 OffsetAndMagic(node.value.col_offset, src)
             )
@@ -435,11 +441,7 @@ def visit_Expr(self, node: ast.Expr) -> None:
         and we look for instances of any of the latter.
         """
         if isinstance(node.value, ast.Call) and _is_ipython_magic(node.value.func):
-            args = []
-            for arg in node.value.args:
-                assert isinstance(arg, ast.Str)
-                args.append(arg.s)
-            assert args
+            args = _get_str_args(node.value.args)
             if node.value.func.attr == "run_line_magic":
                 if args[0] == "pinfo":
                     src = f"?{args[1]}"