starlark_syntax/
dialect.rs

1/*
2 * Copyright 2018 The Starlark in Rust Authors.
3 * Copyright (c) Facebook, Inc. and its affiliates.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 *     https://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18use dupe::Dupe;
19
20/// How to handle type annotations in Starlark.
21///
22/// If you are enabling types, you will often want to use
23/// `LibraryExtension::Typing` when constructing a `Globals` environment.
24#[derive(Debug, Clone, Copy, Dupe, Eq, PartialEq, Hash)]
25pub enum DialectTypes {
26    /// Prohibit types at parse time.
27    Disable,
28    /// Allow types at parse time, but ignore types at runtime.
29    ParseOnly,
30    /// Check types at runtime.
31    Enable,
32}
33
34/// Starlark language features to enable, e.g. [`Standard`](Dialect::Standard) to follow the Starlark standard.
35#[derive(Debug, Clone, Eq, PartialEq, Hash)]
36pub struct Dialect {
37    /// Are `def` statements permitted.
38    /// Enabled by default.
39    pub enable_def: bool,
40    /// Are `lambda` expressions permitted.
41    /// Enabled by default.
42    pub enable_lambda: bool,
43    /// Are `load` statements permitted.
44    /// Enabled by default.
45    pub enable_load: bool,
46    /// Are `*` keyword-only arguments allowed as per [PEP 3102](https://www.python.org/dev/peps/pep-3102/).
47    /// Disabled by default.
48    pub enable_keyword_only_arguments: bool,
49    /// Are `/` for positional-only arguments allowed.
50    pub enable_positional_only_arguments: bool,
51    /// Are expressions allowed in type positions as per [PEP 484](https://www.python.org/dev/peps/pep-0484/).
52    /// Disabled by default.
53    pub enable_types: DialectTypes,
54    /// Do `load()` statements reexport their definition.
55    /// Enabled by default,
56    /// but may change in future definitions of the standard.
57    pub enable_load_reexport: bool,
58    /// Are `for`, `if` and other statements allowed at the top level.
59    /// Disabled by default.
60    pub enable_top_level_stmt: bool,
61    /// Are `f"{expression}"` strings supported? Only works where `expression` is an atomic
62    /// identifier.
63    /// Disabled by default.
64    ///
65    /// [Starlark spec proposal](https://github.com/bazelbuild/starlark/issues/91).
66    pub enable_f_strings: bool,
67    /// Like `#[non_exhaustive]`, but allows struct expression.
68    ///
69    /// [Explanation](https://github.com/rust-lang/rust-clippy/issues/6559).
70    pub _non_exhaustive: (),
71}
72
73impl Default for Dialect {
74    fn default() -> Dialect {
75        Dialect::Standard
76    }
77}
78
79// These are morally enumerations, so give them enumeration-like names
80// even though they are actually global constants
81#[allow(non_upper_case_globals)]
82impl Dialect {
83    /// Follow the [Starlark language standard](https://github.com/bazelbuild/starlark/blob/master/spec.md) as much as possible.
84    ///
85    /// This is also returned by [`Dialect::default()`](Dialect::default).
86    pub const Standard: Self = Self {
87        enable_def: true,
88        enable_lambda: true,
89        enable_load: true,
90        enable_keyword_only_arguments: false,
91        enable_positional_only_arguments: false,
92        enable_types: DialectTypes::Disable,
93        enable_load_reexport: true, // But they plan to change it
94        enable_top_level_stmt: false,
95        enable_f_strings: false,
96        _non_exhaustive: (),
97    };
98
99    /// This option is deprecated. Extend `Standard` instead.
100    #[doc(hidden)]
101    pub const Extended: Self = Self {
102        enable_def: true,
103        enable_lambda: true,
104        enable_load: true,
105        enable_keyword_only_arguments: true,
106        enable_positional_only_arguments: false,
107        enable_types: DialectTypes::Enable,
108        enable_load_reexport: true,
109        enable_top_level_stmt: true,
110        enable_f_strings: false,
111        _non_exhaustive: (),
112    };
113
114    /// Only for starlark-rust self tests.
115    #[doc(hidden)]
116    pub const AllOptionsInternal: Self = Self {
117        enable_def: true,
118        enable_lambda: true,
119        enable_load: true,
120        enable_keyword_only_arguments: true,
121        enable_positional_only_arguments: true,
122        enable_types: DialectTypes::Enable,
123        enable_load_reexport: true,
124        enable_top_level_stmt: true,
125        enable_f_strings: true,
126        _non_exhaustive: (),
127    };
128}
starlark_syntax/dialect.rs

starlark_syntax/
dialect.rs
