yash-builtin 0.4.0

Implementation of the built-in utilities of yash
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137

// This file is part of yash, an extended POSIX shell.
// Copyright (C) 2023 WATANABE Yuki
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

//! Pwd built-in.
//!
//! The **`pwd`** built-in prints the working directory path.
//!
//! # Synopsis
//!
//! ```sh
//! pwd [-L|-P]
//! ```
//!
//! # Description
//!
//! The built-in prints the pathname of the current working directory followed
//! by a newline to the standard output.
//!
//! # Options
//!
//! With the **`-L`** (**`--logical`**) option, the printed path is the value of
//! `$PWD` if it is correct ([`Env::has_correct_pwd`]). The path may contain
//! symbolic link components.
//!
//! With the **`-P`** (**`--physical`**) option (or if `$PWD` is not correct),
//! the built-in recomputes and prints the canonical path to the working
//! directory.
//!
//! These two options are mutually exclusive. The last specified one applies if
//! given both. The default is `-L`.
//!
//! # Operands
//!
//! None.
//!
//! # Errors
//!
//! This built-in may fail for various reasons. For example:
//! - The working directory has been removed from the file system.
//! - You do not have permission to access the ancestor directories of the working directory.
//! - The standard output is not writable.
//!
//! # Exit Status
//!
//! Zero if the path was successfully printed; non-zero otherwise.
//!
//! # Portability
//!
//! The `-L` and `-P` options are defined in POSIX.
//!
//! POSIX allows the built-in to apply the `-P` option if the `-L` option is
//! specified and `$PWD` is longer than PATH_MAX.
//!
//! The shell sets `$PWD` on the startup and modifies it in the [cd](crate::cd)
//! built-in. If `$PWD` is modified or unset otherwise, the behavior of the cd
//! and pwd built-ins is unspecified.
//!
//! # Implementation notes
//!
//! The result for the `-P` option is obtained with [`System::getcwd`].

use crate::common::arrange_message_and_divert;
use crate::common::output;
use crate::common::report_error;
use std::borrow::Cow;
use yash_env::builtin::Result;
use yash_env::semantics::ExitStatus;
use yash_env::semantics::Field;
use yash_env::Env;
#[cfg(doc)]
use yash_env::System;
use yash_syntax::source::pretty::Annotation;
use yash_syntax::source::pretty::AnnotationType;
use yash_syntax::source::pretty::Message;
use yash_syntax::source::Location;

/// Choice of the behavior of the built-in
#[derive(Debug, Clone, Copy, Default, Eq, Hash, PartialEq)]
#[non_exhaustive]
pub enum Mode {
    /// The built-in prints the value of `$PWD` if it is
    /// [correct](Env::has_correct_pwd).
    ///
    /// If `$PWD` is not a correct path, the built-in falls back to
    /// [`Physical`](Self::Physical).
    #[default]
    Logical,

    /// The built-in computes the canonical path to the working directory.
    Physical,
}

pub mod semantics;
pub mod syntax;

async fn report_semantics_error(env: &mut Env, error: &semantics::Error) -> Result {
    let location = env.stack.current_builtin().map_or_else(
        || Cow::Owned(Location::dummy("")),
        |field| Cow::Borrowed(&field.name.origin),
    );
    let annotation = Annotation::new(AnnotationType::Error, error.to_string().into(), &location);
    let message = Message {
        r#type: AnnotationType::Error,
        title: "cannot compute the working directory path".into(),
        annotations: vec![annotation],
        footers: vec![],
    };
    let (message, divert) = arrange_message_and_divert(env, message);
    env.system.print_error(&message).await;
    Result::with_exit_status_and_divert(ExitStatus::FAILURE, divert)
}

/// Entry point for executing the `pwd` built-in
///
/// This function uses the [`syntax`] and [`semantics`] modules to execute the built-in.
pub async fn main(env: &mut Env, args: Vec<Field>) -> Result {
    match syntax::parse(env, args) {
        Ok(mode) => match semantics::compute(env, mode) {
            Ok(result) => output(env, &result).await,
            Err(e) => report_semantics_error(env, &e).await,
        },
        Err(e) => report_error(env, &e).await,
    }
}