| # Copyright 2025 The Fuchsia Authors. All rights reserved. |
| # Use of this source code is governed by a BSD-style license that can be |
| # found in the LICENSE file. |
| |
| """Starlark related utilities.""" |
| |
| import typing as T |
| |
| |
| def to_starlark_expr(v: T.Any, indent: str = "") -> str: |
| """Convert a Python value to the corresponding Starlark expression. |
| |
| Args: |
| v: input value. |
| indent: optional starting indentation string. Empty by default. |
| this is only used when the output expression spans several |
| lines. |
| Returns: |
| the corresponding Starlark expression as a string. |
| Raises: |
| ValueError if the input value cannot be represented by a |
| Starlark expression. In particular set() values are not |
| supported by the Starlark language. |
| """ |
| return StarlarkFormatter.format(v, indent) |
| |
| |
| class StarlarkFormatter(object): |
| """Implementation class for to_starlark_expr(). |
| |
| Used to avoid redundant string allocations and concatenations during |
| formatting. Instead, each instance contains a single output buffer that |
| is appended to by the various _format_xxx() methods. |
| """ |
| |
| @staticmethod |
| def format(v: T.Any, indent: str) -> str: |
| f = StarlarkFormatter(indent) |
| f._format_value(v) |
| return f._result |
| |
| def __init__(self, indent: str = "") -> None: |
| self._result = "" |
| self._indent = indent |
| |
| def _format_value(self, v: T.Any) -> None: |
| if isinstance(v, list): |
| self._format_list(v) |
| elif isinstance(v, dict): |
| self._format_dict(v) |
| elif isinstance(v, str): |
| self._format_string(v) |
| elif isinstance(v, bool) or isinstance(v, int): |
| self._result += str(v) |
| else: |
| raise ValueError( |
| f"Unknown type of input value: {v} (type={type(v)})" |
| ) |
| |
| def _format_string(self, v: str) -> None: |
| self._result += '"' |
| for c in v: |
| if ord(c) < 32: # non-printable characters. |
| if c == "\b": |
| c = "\\b" |
| elif c == "\r": |
| c = "\\r" |
| elif c == "\f": |
| c = "\\f" |
| elif c == "\n": |
| c = "\\n" |
| elif c == "\t": |
| c = "\\t" |
| else: |
| c = "\\u%02x" % ord(c) |
| elif c == '"': |
| c = '\\"' |
| elif c == "\\": |
| c = "\\\\" |
| self._result += c |
| self._result += '"' |
| |
| def _format_list(self, v: list[T.Any]) -> None: |
| if not v: |
| self._result += "[]" |
| return |
| |
| if len(v) == 1: |
| self._result += "[" |
| self._format_value(v[0]) |
| self._result += "]" |
| return |
| |
| comma = "[" |
| self._indent += " " |
| for item in v: |
| self._result += f"{comma}\n{self._indent}" |
| self._format_value(item) |
| comma = "," |
| |
| self._indent = self._indent[:-4] |
| self._result += f"\n{self._indent}]" |
| |
| def _format_dict(self, v: dict[T.Any, T.Any]) -> None: |
| if not v: |
| self._result += "{}" |
| return |
| |
| if len(v) == 1: |
| key, value = v.popitem() |
| self._result += "{" |
| self._format_value(key) |
| self._result += ": " |
| self._format_value(value) |
| self._result += "}" |
| return |
| |
| comma = "{" |
| self._indent += " " |
| for key, value in v.items(): |
| self._result += f"{comma}\n{self._indent}" |
| self._format_value(key) |
| self._result += ": " |
| self._format_value(value) |
| comma = "," |
| |
| self._indent = self._indent[:-4] |
| self._result += f"\n{self._indent}}}" |
