#
cargo/core/
shell.rs

    1use std::fmt;
    2use std::io::prelude::*;
    3use std::io::IsTerminal;
    4
    5use annotate_snippets::{Message, Renderer};
    6use anstream::AutoStream;
    7use anstyle::Style;
    8
    9use crate::util::errors::CargoResult;
    10use crate::util::hostname;
    11use crate::util::style::*;
    12
    13/// An abstraction around console output that remembers preferences for output
    14/// verbosity and color.
    15pub struct Shell {
    16    /// Wrapper around stdout/stderr. This helps with supporting sending
    17    /// output to a memory buffer which is useful for tests.
    18    output: ShellOut,
    19    /// How verbose messages should be.
    20    verbosity: Verbosity,
    21    /// Flag that indicates the current line needs to be cleared before
    22    /// printing. Used when a progress bar is currently displayed.
    23    needs_clear: bool,
    24    hostname: Option<String>,
    25}
    26
    27impl fmt::Debug for Shell {
    28    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    29        match self.output {
    30            ShellOut::Write(_) => f
    31                .debug_struct("Shell")
    32                .field("verbosity", &self.verbosity)
    33                .finish(),
    34            ShellOut::Stream { color_choice, .. } => f
    35                .debug_struct("Shell")
    36                .field("verbosity", &self.verbosity)
    37                .field("color_choice", &color_choice)
    38                .finish(),
    39        }
    40    }
    41}
    42
    43impl Shell {
    44    /// Creates a new shell (color choice and verbosity), defaulting to 'auto' color and verbose
    45    /// output.
    46    pub fn new() -> Shell {
    47        let auto_clr = ColorChoice::CargoAuto;
    48        let stdout_choice = auto_clr.to_anstream_color_choice();
    49        let stderr_choice = auto_clr.to_anstream_color_choice();
    50        Shell {
    51            output: ShellOut::Stream {
    52                stdout: AutoStream::new(std::io::stdout(), stdout_choice),
    53                stderr: AutoStream::new(std::io::stderr(), stderr_choice),
    54                color_choice: auto_clr,
    55                hyperlinks: supports_hyperlinks(),
    56                stderr_tty: std::io::stderr().is_terminal(),
    57                stdout_unicode: supports_unicode(&std::io::stdout()),
    58                stderr_unicode: supports_unicode(&std::io::stderr()),
    59                stderr_term_integration: supports_term_integration(&std::io::stderr()),
    60            },
    61            verbosity: Verbosity::Verbose,
    62            needs_clear: false,
    63            hostname: None,
    64        }
    65    }
    66
    67    /// Creates a shell from a plain writable object, with no color, and max verbosity.
    68    pub fn from_write(out: Box<dyn Write>) -> Shell {
    69        Shell {
    70            output: ShellOut::Write(AutoStream::never(out)), // strip all formatting on write
    71            verbosity: Verbosity::Verbose,
    72            needs_clear: false,
    73            hostname: None,
    74        }
    75    }
    76
    77    /// Prints a message, where the status will have `color` color, and can be justified. The
    78    /// messages follows without color.
    79    fn print(
    80        &mut self,
    81        status: &dyn fmt::Display,
    82        message: Option<&dyn fmt::Display>,
    83        color: &Style,
    84        justified: bool,
    85    ) -> CargoResult<()> {
    86        match self.verbosity {
    87            Verbosity::Quiet => Ok(()),
    88            _ => {
    89                if self.needs_clear {
    90                    self.err_erase_line();
    91                }
    92                self.output
    93                    .message_stderr(status, message, color, justified)
    94            }
    95        }
    96    }
    97
    98    /// Sets whether the next print should clear the current line.
    99    pub fn set_needs_clear(&mut self, needs_clear: bool) {
    100        self.needs_clear = needs_clear;
    101    }
    102
    103    /// Returns `true` if the `needs_clear` flag is unset.
    104    pub fn is_cleared(&self) -> bool {
    105        !self.needs_clear
    106    }
    107
    108    /// Returns the width of the terminal in spaces, if any.
    109    pub fn err_width(&self) -> TtyWidth {
    110        match self.output {
    111            ShellOut::Stream {
    112                stderr_tty: true, ..
    113            } => imp::stderr_width(),
    114            _ => TtyWidth::NoTty,
    115        }
    116    }
    117
    118    /// Returns `true` if stderr is a tty.
    119    pub fn is_err_tty(&self) -> bool {
    120        match self.output {
    121            ShellOut::Stream { stderr_tty, .. } => stderr_tty,
    122            _ => false,
    123        }
    124    }
    125
    126    pub fn is_err_term_integration_available(&self) -> bool {
    127        if let ShellOut::Stream {
    128            stderr_term_integration,
    129            ..
    130        } = self.output
    131        {
    132            stderr_term_integration
    133        } else {
    134            false
    135        }
    136    }
    137
    138    /// Gets a reference to the underlying stdout writer.
    139    pub fn out(&mut self) -> &mut dyn Write {
    140        if self.needs_clear {
    141            self.err_erase_line();
    142        }
    143        self.output.stdout()
    144    }
    145
    146    /// Gets a reference to the underlying stderr writer.
    147    pub fn err(&mut self) -> &mut dyn Write {
    148        if self.needs_clear {
    149            self.err_erase_line();
    150        }
    151        self.output.stderr()
    152    }
    153
    154    /// Erase from cursor to end of line.
    155    pub fn err_erase_line(&mut self) {
    156        if self.err_supports_color() {
    157            imp::err_erase_line(self);
    158            self.needs_clear = false;
    159        }
    160    }
    161
    162    /// Shortcut to right-align and color green a status message.
    163    pub fn status<T, U>(&mut self, status: T, message: U) -> CargoResult<()>
    164    where
    165        T: fmt::Display,
    166        U: fmt::Display,
    167    {
    168        self.print(&status, Some(&message), &HEADER, true)
    169    }
    170
    171    pub fn status_header<T>(&mut self, status: T) -> CargoResult<()>
    172    where
    173        T: fmt::Display,
    174    {
    175        self.print(&status, None, &NOTE, true)
    176    }
    177
    178    /// Shortcut to right-align a status message.
    179    pub fn status_with_color<T, U>(
    180        &mut self,
    181        status: T,
    182        message: U,
    183        color: &Style,
    184    ) -> CargoResult<()>
    185    where
    186        T: fmt::Display,
    187        U: fmt::Display,
    188    {
    189        self.print(&status, Some(&message), color, true)
    190    }
    191
    192    /// Runs the callback only if we are in verbose mode.
    193    pub fn verbose<F>(&mut self, mut callback: F) -> CargoResult<()>
    194    where
    195        F: FnMut(&mut Shell) -> CargoResult<()>,
    196    {
    197        match self.verbosity {
    198            Verbosity::Verbose => callback(self),
    199            _ => Ok(()),
    200        }
    201    }
    202
    203    /// Runs the callback if we are not in verbose mode.
    204    pub fn concise<F>(&mut self, mut callback: F) -> CargoResult<()>
    205    where
    206        F: FnMut(&mut Shell) -> CargoResult<()>,
    207    {
    208        match self.verbosity {
    209            Verbosity::Verbose => Ok(()),
    210            _ => callback(self),
    211        }
    212    }
    213
    214    /// Prints a red 'error' message.
    215    pub fn error<T: fmt::Display>(&mut self, message: T) -> CargoResult<()> {
    216        if self.needs_clear {
    217            self.err_erase_line();
    218        }
    219        self.output
    220            .message_stderr(&"error", Some(&message), &ERROR, false)
    221    }
    222
    223    /// Prints an amber 'warning' message.
    224    pub fn warn<T: fmt::Display>(&mut self, message: T) -> CargoResult<()> {
    225        match self.verbosity {
    226            Verbosity::Quiet => Ok(()),
    227            _ => self.print(&"warning", Some(&message), &WARN, false),
    228        }
    229    }
    230
    231    /// Prints a cyan 'note' message.
    232    pub fn note<T: fmt::Display>(&mut self, message: T) -> CargoResult<()> {
    233        self.print(&"note", Some(&message), &NOTE, false)
    234    }
    235
    236    /// Updates the verbosity of the shell.
    237    pub fn set_verbosity(&mut self, verbosity: Verbosity) {
    238        self.verbosity = verbosity;
    239    }
    240
    241    /// Gets the verbosity of the shell.
    242    pub fn verbosity(&self) -> Verbosity {
    243        self.verbosity
    244    }
    245
    246    /// Updates the color choice (always, never, or auto) from a string..
    247    pub fn set_color_choice(&mut self, color: Option<&str>) -> CargoResult<()> {
    248        if let ShellOut::Stream {
    249            stdout,
    250            stderr,
    251            color_choice,
    252            ..
    253        } = &mut self.output
    254        {
    255            let cfg = color
    256                .map(|c| c.parse())
    257                .transpose()?
    258                .unwrap_or(ColorChoice::CargoAuto);
    259            *color_choice = cfg;
    260            let stdout_choice = cfg.to_anstream_color_choice();
    261            let stderr_choice = cfg.to_anstream_color_choice();
    262            *stdout = AutoStream::new(std::io::stdout(), stdout_choice);
    263            *stderr = AutoStream::new(std::io::stderr(), stderr_choice);
    264        }
    265        Ok(())
    266    }
    267
    268    pub fn set_unicode(&mut self, yes: bool) -> CargoResult<()> {
    269        if let ShellOut::Stream {
    270            stdout_unicode,
    271            stderr_unicode,
    272            ..
    273        } = &mut self.output
    274        {
    275            *stdout_unicode = yes;
    276            *stderr_unicode = yes;
    277        }
    278        Ok(())
    279    }
    280
    281    pub fn set_hyperlinks(&mut self, yes: bool) -> CargoResult<()> {
    282        if let ShellOut::Stream { hyperlinks, .. } = &mut self.output {
    283            *hyperlinks = yes;
    284        }
    285        Ok(())
    286    }
    287
    288    pub fn out_unicode(&self) -> bool {
    289        match &self.output {
    290            ShellOut::Write(_) => true,
    291            ShellOut::Stream { stdout_unicode, .. } => *stdout_unicode,
    292        }
    293    }
    294
    295    pub fn err_unicode(&self) -> bool {
    296        match &self.output {
    297            ShellOut::Write(_) => true,
    298            ShellOut::Stream { stderr_unicode, .. } => *stderr_unicode,
    299        }
    300    }
    301
    302    /// Gets the current color choice.
    303    ///
    304    /// If we are not using a color stream, this will always return `Never`, even if the color
    305    /// choice has been set to something else.
    306    pub fn color_choice(&self) -> ColorChoice {
    307        match self.output {
    308            ShellOut::Stream { color_choice, .. } => color_choice,
    309            ShellOut::Write(_) => ColorChoice::Never,
    310        }
    311    }
    312
    313    /// Whether the shell supports color.
    314    pub fn err_supports_color(&self) -> bool {
    315        match &self.output {
    316            ShellOut::Write(_) => false,
    317            ShellOut::Stream { stderr, .. } => supports_color(stderr.current_choice()),
    318        }
    319    }
    320
    321    pub fn out_supports_color(&self) -> bool {
    322        match &self.output {
    323            ShellOut::Write(_) => false,
    324            ShellOut::Stream { stdout, .. } => supports_color(stdout.current_choice()),
    325        }
    326    }
    327
    328    pub fn out_hyperlink<D: fmt::Display>(&self, url: D) -> Hyperlink<D> {
    329        let supports_hyperlinks = match &self.output {
    330            ShellOut::Write(_) => false,
    331            ShellOut::Stream {
    332                stdout, hyperlinks, ..
    333            } => stdout.current_choice() == anstream::ColorChoice::AlwaysAnsi && *hyperlinks,
    334        };
    335        Hyperlink {
    336            url: supports_hyperlinks.then_some(url),
    337        }
    338    }
    339
    340    pub fn err_hyperlink<D: fmt::Display>(&self, url: D) -> Hyperlink<D> {
    341        let supports_hyperlinks = match &self.output {
    342            ShellOut::Write(_) => false,
    343            ShellOut::Stream {
    344                stderr, hyperlinks, ..
    345            } => stderr.current_choice() == anstream::ColorChoice::AlwaysAnsi && *hyperlinks,
    346        };
    347        if supports_hyperlinks {
    348            Hyperlink { url: Some(url) }
    349        } else {
    350            Hyperlink { url: None }
    351        }
    352    }
    353
    354    pub fn out_file_hyperlink(&mut self, path: &std::path::Path) -> Hyperlink<url::Url> {
    355        let url = self.file_hyperlink(path);
    356        url.map(|u| self.out_hyperlink(u)).unwrap_or_default()
    357    }
    358
    359    pub fn err_file_hyperlink(&mut self, path: &std::path::Path) -> Hyperlink<url::Url> {
    360        let url = self.file_hyperlink(path);
    361        url.map(|u| self.err_hyperlink(u)).unwrap_or_default()
    362    }
    363
    364    fn file_hyperlink(&mut self, path: &std::path::Path) -> Option<url::Url> {
    365        let mut url = url::Url::from_file_path(path).ok()?;
    366        // Do a best-effort of setting the host in the URL to avoid issues with opening a link
    367        // scoped to the computer you've SSHed into
    368        let hostname = if cfg!(windows) {
    369            // Not supported correctly on windows
    370            None
    371        } else {
    372            if let Some(hostname) = self.hostname.as_deref() {
    373                Some(hostname)
    374            } else {
    375                self.hostname = hostname().ok().and_then(|h| h.into_string().ok());
    376                self.hostname.as_deref()
    377            }
    378        };
    379        let _ = url.set_host(hostname);
    380        Some(url)
    381    }
    382
    383    /// Prints a message to stderr and translates ANSI escape code into console colors.
    384    pub fn print_ansi_stderr(&mut self, message: &[u8]) -> CargoResult<()> {
    385        if self.needs_clear {
    386            self.err_erase_line();
    387        }
    388        self.err().write_all(message)?;
    389        Ok(())
    390    }
    391
    392    /// Prints a message to stdout and translates ANSI escape code into console colors.
    393    pub fn print_ansi_stdout(&mut self, message: &[u8]) -> CargoResult<()> {
    394        if self.needs_clear {
    395            self.err_erase_line();
    396        }
    397        self.out().write_all(message)?;
    398        Ok(())
    399    }
    400
    401    pub fn print_json<T: serde::ser::Serialize>(&mut self, obj: &T) -> CargoResult<()> {
    402        // Path may fail to serialize to JSON ...
    403        let encoded = serde_json::to_string(&obj)?;
    404        // ... but don't fail due to a closed pipe.
    405        drop(writeln!(self.out(), "{}", encoded));
    406        Ok(())
    407    }
    408
    409    /// Prints the passed in [Message] to stderr
    410    pub fn print_message(&mut self, message: Message<'_>) -> std::io::Result<()> {
    411        let term_width = self
    412            .err_width()
    413            .diagnostic_terminal_width()
    414            .unwrap_or(annotate_snippets::renderer::DEFAULT_TERM_WIDTH);
    415        writeln!(
    416            self.err(),
    417            "{}",
    418            Renderer::styled().term_width(term_width).render(message)
    419        )
    420    }
    421}
    422
    423impl Default for Shell {
    424    fn default() -> Self {
    425        Self::new()
    426    }
    427}
    428
    429/// A `Write`able object, either with or without color support
    430enum ShellOut {
    431    /// A plain write object without color support
    432    Write(AutoStream<Box<dyn Write>>),
    433    /// Color-enabled stdio, with information on whether color should be used
    434    Stream {
    435        stdout: AutoStream<std::io::Stdout>,
    436        stderr: AutoStream<std::io::Stderr>,
    437        stderr_tty: bool,
    438        color_choice: ColorChoice,
    439        hyperlinks: bool,
    440        stdout_unicode: bool,
    441        stderr_unicode: bool,
    442        stderr_term_integration: bool,
    443    },
    444}
    445
    446impl ShellOut {
    447    /// Prints out a message with a status. The status comes first, and is bold plus the given
    448    /// color. The status can be justified, in which case the max width that will right align is
    449    /// 12 chars.
    450    fn message_stderr(
    451        &mut self,
    452        status: &dyn fmt::Display,
    453        message: Option<&dyn fmt::Display>,
    454        style: &Style,
    455        justified: bool,
    456    ) -> CargoResult<()> {
    457        let bold = anstyle::Style::new() | anstyle::Effects::BOLD;
    458
    459        let mut buffer = Vec::new();
    460        if justified {
    461            write!(&mut buffer, "{style}{status:>12}{style:#}")?;
    462        } else {
    463            write!(&mut buffer, "{style}{status}{style:#}{bold}:{bold:#}")?;
    464        }
    465        match message {
    466            Some(message) => writeln!(buffer, " {message}")?,
    467            None => write!(buffer, " ")?,
    468        }
    469        self.stderr().write_all(&buffer)?;
    470        Ok(())
    471    }
    472
    473    /// Gets stdout as a `io::Write`.
    474    fn stdout(&mut self) -> &mut dyn Write {
    475        match self {
    476            ShellOut::Stream { stdout, .. } => stdout,
    477            ShellOut::Write(w) => w,
    478        }
    479    }
    480
    481    /// Gets stderr as a `io::Write`.
    482    fn stderr(&mut self) -> &mut dyn Write {
    483        match self {
    484            ShellOut::Stream { stderr, .. } => stderr,
    485            ShellOut::Write(w) => w,
    486        }
    487    }
    488}
    489
    490pub enum TtyWidth {
    491    NoTty,
    492    Known(usize),
    493    Guess(usize),
    494}
    495
    496impl TtyWidth {
    497    /// Returns the width of the terminal to use for diagnostics (which is
    498    /// relayed to rustc via `--diagnostic-width`).
    499    pub fn diagnostic_terminal_width(&self) -> Option<usize> {
    500        // ALLOWED: For testing cargo itself only.
    501        #[allow(clippy::disallowed_methods)]
    502        if let Ok(width) = std::env::var("__CARGO_TEST_TTY_WIDTH_DO_NOT_USE_THIS") {
    503            return Some(width.parse().unwrap());
    504        }
    505        match *self {
    506            TtyWidth::NoTty | TtyWidth::Guess(_) => None,
    507            TtyWidth::Known(width) => Some(width),
    508        }
    509    }
    510
    511    /// Returns the width used by progress bars for the tty.
    512    pub fn progress_max_width(&self) -> Option<usize> {
    513        match *self {
    514            TtyWidth::NoTty => None,
    515            TtyWidth::Known(width) | TtyWidth::Guess(width) => Some(width),
    516        }
    517    }
    518}
    519
    520/// The requested verbosity of output.
    521#[derive(Debug, Clone, Copy, PartialEq)]
    522pub enum Verbosity {
    523    Verbose,
    524    Normal,
    525    Quiet,
    526}
    527
    528/// Whether messages should use color output
    529#[derive(Debug, PartialEq, Clone, Copy)]
    530pub enum ColorChoice {
    531    /// Force color output
    532    Always,
    533    /// Force disable color output
    534    Never,
    535    /// Intelligently guess whether to use color output
    536    CargoAuto,
    537}
    538
    539impl ColorChoice {
    540    /// Converts our color choice to anstream's version.
    541    fn to_anstream_color_choice(self) -> anstream::ColorChoice {
    542        match self {
    543            ColorChoice::Always => anstream::ColorChoice::Always,
    544            ColorChoice::Never => anstream::ColorChoice::Never,
    545            ColorChoice::CargoAuto => anstream::ColorChoice::Auto,
    546        }
    547    }
    548}
    549
    550impl std::str::FromStr for ColorChoice {
    551    type Err = anyhow::Error;
    552    fn from_str(color: &str) -> Result<Self, Self::Err> {
    553        let cfg = match color {
    554            "always" => ColorChoice::Always,
    555            "never" => ColorChoice::Never,
    556
    557            "auto" => ColorChoice::CargoAuto,
    558
    559            arg => anyhow::bail!(
    560                "argument for --color must be auto, always, or \
    561                     never, but found `{}`",
    562                arg
    563            ),
    564        };
    565        Ok(cfg)
    566    }
    567}
    568
    569fn supports_color(choice: anstream::ColorChoice) -> bool {
    570    match choice {
    571        anstream::ColorChoice::Always
    572        | anstream::ColorChoice::AlwaysAnsi
    573        | anstream::ColorChoice::Auto => true,
    574        anstream::ColorChoice::Never => false,
    575    }
    576}
    577
    578fn supports_unicode(stream: &dyn IsTerminal) -> bool {
    579    !stream.is_terminal() || supports_unicode::supports_unicode()
    580}
    581
    582fn supports_hyperlinks() -> bool {
    583    #[allow(clippy::disallowed_methods)] // We are reading the state of the system, not config
    584    if std::env::var_os("TERM_PROGRAM").as_deref() == Some(std::ffi::OsStr::new("iTerm.app")) {
    585        // Override `supports_hyperlinks` as we have an unknown incompatibility with iTerm2
    586        return false;
    587    }
    588
    589    supports_hyperlinks::supports_hyperlinks()
    590}
    591
    592/// Determines whether the terminal supports ANSI OSC 9;4.
    593#[allow(clippy::disallowed_methods)] // Read environment variables to detect terminal
    594fn supports_term_integration(stream: &dyn IsTerminal) -> bool {
    595    let windows_terminal = std::env::var("WT_SESSION").is_ok();
    596    let conemu = std::env::var("ConEmuANSI").ok() == Some("ON".into());
    597    let wezterm = std::env::var("TERM_PROGRAM").ok() == Some("WezTerm".into());
    598
    599    (windows_terminal || conemu || wezterm) && stream.is_terminal()
    600}
    601
    602pub struct Hyperlink<D: fmt::Display> {
    603    url: Option<D>,
    604}
    605
    606impl<D: fmt::Display> Default for Hyperlink<D> {
    607    fn default() -> Self {
    608        Self { url: None }
    609    }
    610}
    611
    612impl<D: fmt::Display> fmt::Display for Hyperlink<D> {
    613    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    614        let Some(url) = self.url.as_ref() else {
    615            return Ok(());
    616        };
    617        if f.alternate() {
    618            write!(f, "\x1B]8;;\x1B\\")
    619        } else {
    620            write!(f, "\x1B]8;;{url}\x1B\\")
    621        }
    622    }
    623}
    624
    625#[cfg(unix)]
    626mod imp {
    627    use super::{Shell, TtyWidth};
    628    use std::mem;
    629
    630    pub fn stderr_width() -> TtyWidth {
    631        unsafe {
    632            let mut winsize: libc::winsize = mem::zeroed();
    633            // The .into() here is needed for FreeBSD which defines TIOCGWINSZ
    634            // as c_uint but ioctl wants c_ulong.
    635            if libc::ioctl(libc::STDERR_FILENO, libc::TIOCGWINSZ.into(), &mut winsize) < 0 {
    636                return TtyWidth::NoTty;
    637            }
    638            if winsize.ws_col > 0 {
    639                TtyWidth::Known(winsize.ws_col as usize)
    640            } else {
    641                TtyWidth::NoTty
    642            }
    643        }
    644    }
    645
    646    pub fn err_erase_line(shell: &mut Shell) {
    647        // This is the "EL - Erase in Line" sequence. It clears from the cursor
    648        // to the end of line.
    649        // https://en.wikipedia.org/wiki/ANSI_escape_code#CSI_sequences
    650        let _ = shell.output.stderr().write_all(b"\x1B[K");
    651    }
    652}
    653
    654#[cfg(windows)]
    655mod imp {
    656    use std::{cmp, mem, ptr};
    657
    658    use windows_sys::core::PCSTR;
    659    use windows_sys::Win32::Foundation::CloseHandle;
    660    use windows_sys::Win32::Foundation::INVALID_HANDLE_VALUE;
    661    use windows_sys::Win32::Foundation::{GENERIC_READ, GENERIC_WRITE};
    662    use windows_sys::Win32::Storage::FileSystem::{
    663        CreateFileA, FILE_SHARE_READ, FILE_SHARE_WRITE, OPEN_EXISTING,
    664    };
    665    use windows_sys::Win32::System::Console::{
    666        GetConsoleScreenBufferInfo, GetStdHandle, CONSOLE_SCREEN_BUFFER_INFO, STD_ERROR_HANDLE,
    667    };
    668
    669    pub(super) use super::{default_err_erase_line as err_erase_line, TtyWidth};
    670
    671    pub fn stderr_width() -> TtyWidth {
    672        unsafe {
    673            let stdout = GetStdHandle(STD_ERROR_HANDLE);
    674            let mut csbi: CONSOLE_SCREEN_BUFFER_INFO = mem::zeroed();
    675            if GetConsoleScreenBufferInfo(stdout, &mut csbi) != 0 {
    676                return TtyWidth::Known((csbi.srWindow.Right - csbi.srWindow.Left) as usize);
    677            }
    678
    679            // On mintty/msys/cygwin based terminals, the above fails with
    680            // INVALID_HANDLE_VALUE. Use an alternate method which works
    681            // in that case as well.
    682            let h = CreateFileA(
    683                "CONOUT$\0".as_ptr() as PCSTR,
    684                GENERIC_READ | GENERIC_WRITE,
    685                FILE_SHARE_READ | FILE_SHARE_WRITE,
    686                ptr::null_mut(),
    687                OPEN_EXISTING,
    688                0,
    689                std::ptr::null_mut(),
    690            );
    691            if h == INVALID_HANDLE_VALUE {
    692                return TtyWidth::NoTty;
    693            }
    694
    695            let mut csbi: CONSOLE_SCREEN_BUFFER_INFO = mem::zeroed();
    696            let rc = GetConsoleScreenBufferInfo(h, &mut csbi);
    697            CloseHandle(h);
    698            if rc != 0 {
    699                let width = (csbi.srWindow.Right - csbi.srWindow.Left) as usize;
    700                // Unfortunately cygwin/mintty does not set the size of the
    701                // backing console to match the actual window size. This
    702                // always reports a size of 80 or 120 (not sure what
    703                // determines that). Use a conservative max of 60 which should
    704                // work in most circumstances. ConEmu does some magic to
    705                // resize the console correctly, but there's no reasonable way
    706                // to detect which kind of terminal we are running in, or if
    707                // GetConsoleScreenBufferInfo returns accurate information.
    708                return TtyWidth::Guess(cmp::min(60, width));
    709            }
    710
    711            TtyWidth::NoTty
    712        }
    713    }
    714}
    715
    716#[cfg(windows)]
    717fn default_err_erase_line(shell: &mut Shell) {
    718    match imp::stderr_width() {
    719        TtyWidth::Known(max_width) | TtyWidth::Guess(max_width) => {
    720            let blank = " ".repeat(max_width);
    721            drop(write!(shell.output.stderr(), "{}\r", blank));
    722        }
    723        _ => (),
    724    }
    725}