libtmux 0.1.0-alpha.12

//! The shared path from a list command to hydrated snapshots.
//!
//! Every public listing follows the same four steps: build a format plan for
//! the detected tmux version, render its template into a list command, parse
//! the transport bytes, and hydrate rows. Keeping that here means the public
//! handles differ only in the target they scope to.

use std::ffi::{OsStr, OsString};

use crate::error::ListingDecodeError;
use crate::formats::{FormatCodecError, FormatPlan, ListProfile};
use crate::internal::core::Core;
use crate::snapshot::{
    ClientInfo, PaneProjection, SessionInfo, WindowProjection, hydrate_client_infos_from_stdout,
    hydrate_pane_projections_from_stdout, hydrate_session_infos_from_stdout,
    hydrate_window_projections_from_stdout, pane_projection_plan, window_projection_plan,
};
use crate::{Command, Error};

/// How a listing is scoped.
///
/// tmux spells "everything on the server" and "everything under this object"
/// with different flags, so the two are distinguished here rather than by
/// passing an optional target that callers could forget.
#[derive(Clone, Copy, Debug)]
pub(crate) enum Scope<'target> {
    /// Every object on the server, using tmux's `-a` flag.
    Server,
    /// Only objects under one target, using tmux's `-t` flag.
    ///
    /// For `list-panes` the target is a window; tmux resolves a session target
    /// to that session's current window, which is rarely what a caller means.
    Target(&'target str),
    /// Every pane in one session, using tmux's `-s -t` flags.
    ///
    /// `list-panes` needs `-s` to widen a session target from the current
    /// window to the whole session.
    SessionTarget(&'target str),
    /// No scoping flag, for commands that are already server-wide.
    ///
    /// `list-sessions` and `list-clients` cover the whole server and reject
    /// `-a`, so they take neither flag.
    Unscoped,
}

impl<'target> Scope<'target> {
    /// Return the target this scope names, if it names one.
    const fn target(self) -> Option<&'target str> {
        match self {
            Self::Target(target) | Self::SessionTarget(target) => Some(target),
            Self::Server | Self::Unscoped => None,
        }
    }

    /// Apply this scope's flags to a list command.
    fn apply(self, command: Command) -> Command {
        match self {
            Self::Server => command.arg("-a"),
            Self::Target(target) => command.arg("-t").arg(OsString::from(target)),
            Self::SessionTarget(target) => command.arg("-s").arg("-t").arg(OsString::from(target)),
            Self::Unscoped => command,
        }
    }
}

/// A value that may be interpolated into a tmux `-f` predicate.
///
/// tmux documents no escaping for a predicate, so a value that could contain
/// `#`, `}`, or a comma would change what the predicate means. Only values
/// drawn from a validated domain implement this: an id is a sigil followed by
/// digits, and an index is an integer. A name is user-chosen text and is
/// deliberately absent, which is what keeps the rule enforced by the compiler
/// rather than by remembering it.
pub(crate) trait Pushdown {
    /// Render this value as a tmux predicate comparing one format field.
    fn predicate(&self, field: &str) -> String;
}

macro_rules! pushdown_via_display {
    ($($type:ty),+ $(,)?) => {
        $(impl Pushdown for $type {
            fn predicate(&self, field: &str) -> String {
                format!("#{{==:#{{{field}}},{self}}}")
            }
        })+
    };
}

pushdown_via_display!(crate::SessionId, crate::WindowId, crate::PaneId, i32, u32,);

/// Run one list command and return its raw stdout.
async fn list(
    core: &Core,
    list_command: &'static str,
    scope: Scope<'_>,
    filter: Option<&str>,
    template: &str,
) -> Result<Vec<u8>, Error> {
    let mut command = scope.apply(Command::new(list_command));
    // tmux evaluates the predicate per row, so a filtered listing returns only
    // matching rows rather than every row for the caller to scan.
    if let Some(filter) = filter {
        command = command.arg("-f").arg(OsString::from(filter));
    }
    let result = core
        .execute(command.arg("-F").arg(OsString::from(template)))
        .await?;
    if !result.success() {
        let stderr = result.stderr_lossy().into_owned();
        // A server holding no sessions has no current target, and tmux says
        // so even for `-a`, which asks for everything. A server-wide listing
        // has nothing to list; a listing under a target could not resolve it,
        // which the classifier reports as the target being gone.
        if scope.target().is_none() && stderr.trim_end() == crate::error::NO_CURRENT_TARGET {
            return Ok(Vec::new());
        }

        // Anything else is not an empty listing. The lenient accessors turn
        // this back into an empty Vec; the loud forms exist so a caller who
        // must not guess gets the reason instead.
        return Err(Error::from_refused_result(
            list_command,
            &result,
            scope.target().map(OsStr::new),
        ));
    }

    Ok(result.stdout().to_vec())
}

/// Convert a private codec failure into the public listing error.
fn decode_error(list_command: &'static str) -> impl Fn(FormatCodecError) -> Error {
    move |error| Error::DecodeListing {
        list_command,
        detail: ListingDecodeError::new(error),
    }
}

/// List sessions.
pub(crate) async fn sessions(core: &Core, filter: Option<&str>) -> Result<Vec<SessionInfo>, Error> {
    const LIST_COMMAND: &str = "list-sessions";

    let version = core.capabilities().await?.tmux_version().clone();
    let plan = FormatPlan::for_profile(ListProfile::Sessions, &version);
    let stdout = list(core, LIST_COMMAND, Scope::Unscoped, filter, plan.template()).await?;

    hydrate_session_infos_from_stdout(&plan, &stdout).map_err(decode_error(LIST_COMMAND))
}

/// List windows, either server-wide or under one target.
pub(crate) async fn windows(
    core: &Core,
    scope: Scope<'_>,
    filter: Option<&str>,
) -> Result<Vec<WindowProjection>, Error> {
    const LIST_COMMAND: &str = "list-windows";

    let version = core.capabilities().await?.tmux_version().clone();
    let plan = window_projection_plan(&version).map_err(decode_error(LIST_COMMAND))?;
    let stdout = list(core, LIST_COMMAND, scope, filter, plan.template()).await?;

    hydrate_window_projections_from_stdout(core.configuration().identity(), &plan, &stdout)
        .map_err(decode_error(LIST_COMMAND))
}

/// Resolve one pane and hydrate its containing window from the same tmux row.
pub(crate) async fn window_for_pane(
    core: &Core,
    pane: &crate::PaneId,
) -> Result<Option<WindowProjection>, Error> {
    const LIST_COMMAND: &str = "list-panes";

    let version = core.capabilities().await?.tmux_version().clone();
    let plan = window_projection_plan(&version).map_err(decode_error(LIST_COMMAND))?;
    let target = pane.to_string();
    let filter = pane.predicate("pane_id");
    let stdout = match list(
        core,
        LIST_COMMAND,
        Scope::Target(&target),
        Some(&filter),
        plan.template(),
    )
    .await
    {
        Err(error) if error.is_object_gone() => return Ok(None),
        result => result?,
    };

    Ok(
        hydrate_window_projections_from_stdout(core.configuration().identity(), &plan, &stdout)
            .map_err(decode_error(LIST_COMMAND))?
            .into_iter()
            .next(),
    )
}

/// List panes, either server-wide or under one target.
pub(crate) async fn panes(
    core: &Core,
    scope: Scope<'_>,
    filter: Option<&str>,
) -> Result<Vec<PaneProjection>, Error> {
    const LIST_COMMAND: &str = "list-panes";

    let version = core.capabilities().await?.tmux_version().clone();
    let plan = pane_projection_plan(&version).map_err(decode_error(LIST_COMMAND))?;
    let stdout = list(core, LIST_COMMAND, scope, filter, plan.template()).await?;

    hydrate_pane_projections_from_stdout(core.configuration().identity(), &plan, &stdout)
        .map_err(decode_error(LIST_COMMAND))
}

/// List attached clients.
pub(crate) async fn clients(core: &Core, filter: Option<&str>) -> Result<Vec<ClientInfo>, Error> {
    const LIST_COMMAND: &str = "list-clients";

    let version = core.capabilities().await?.tmux_version().clone();
    let plan = FormatPlan::for_profile(ListProfile::Clients, &version);
    let stdout = list(core, LIST_COMMAND, Scope::Unscoped, filter, plan.template()).await?;

    hydrate_client_infos_from_stdout(&plan, &stdout).map_err(decode_error(LIST_COMMAND))
}

/// The command that renders a format in one client's context.
const IN_CLIENT: &str = "display-message";

/// Render a listing template in one client's context and hydrate one row.
///
/// tmux runs `display-message` through the same format machinery as a list
/// command, and fills in what the client implies: `format_defaults` takes the
/// session from the client, the window from that session's current window, and
/// the pane from that window's active pane. So one round trip returns the whole
/// snapshot, where asking for an id and then listing the object that owns it
/// costs two. The row is byte-identical to the matching `list-sessions -f` row,
/// `#{q:}` escaping included.
///
/// `None` when the client is attached to nothing, which is an ordinary state.
/// The template is wrapped in `#{?session_id,...,}` so tmux expands it to
/// nothing in that case: a format plan asks for fields that are `Required`, and
/// hydrating a row of empty ones would report a decode failure for a client
/// that is simply not attached yet. Nesting is safe because a plan's template
/// is `#{q:<name>}=` repeated and a tmux format name carries no comma.
///
/// This is the one route where a plan's `FIELD_SEPARATOR` must not be `%`.
/// `display-message` expands through `format_expand_time`
/// (`cmd-display-message.c:141`), which runs the template through `strftime`
/// before tmux reads a single `#{`; a list command calls `format_expand`
/// (`cmd-list-clients.c:99`) and never time-expands. Apple's libc drops the
/// `%` of a conversion it does not define and keeps the character alone, so a
/// `%`-separated template would arrive here with its separators eaten and the
/// row would fail to decode on macOS and nowhere else. The separator is
/// chosen in `formats/row.rs` to keep this template free of `%` entirely.
///
/// Targeted with `-t` rather than `-c`, and that is not a preference.
/// `display-message`'s option string is `acd:INpt:F:v` on 3.2a, where `c`
/// carries no colon and so takes no argument: a client name after it becomes a
/// positional argument, the command exceeds its one-argument maximum, and tmux
/// answers with a usage error while every format expands empty. `-c` gained its
/// argument in 3.5a. The usage line on 3.2a advertises `[-c target-client]`
/// anyway, on the line after the option string that refuses it, so the error
/// quotes the flag it just rejected and reads as a typo rather than as a
/// disagreement between tmux's help and its parser.
///
/// `-t` resolves a client on every supported release. Verified to report the
/// target rather than the caller, which the obvious probe cannot show: the
/// asking process and the client usually share a `TERM`, so a wrong answer is
/// byte-identical to a right one. With the client attached as
/// `screen-256color` and the caller at `vt100`, 3.2a and 3.7c both answer
/// `screen-256color`.
async fn in_client_context<T>(
    core: &Core,
    client: &OsStr,
    plan: &FormatPlan,
    hydrate: impl FnOnce(&FormatPlan, &[u8]) -> Result<Vec<T>, FormatCodecError>,
) -> Result<Option<T>, Error> {
    let guarded = format!("#{{?session_id,{},}}", plan.template());
    let result = core
        .execute(
            Command::new(IN_CLIENT)
                .arg("-p")
                .arg("-t")
                .arg(client.to_os_string())
                .arg(OsString::from(guarded)),
        )
        .await?;

    if !result.success() {
        let stderr = result.stderr_lossy();
        if stderr.trim_end() == crate::error::NO_CURRENT_CLIENT {
            return Ok(None);
        }
        return Err(Error::from_refused_result(IN_CLIENT, &result, None));
    }

    let stdout = result.stdout();
    if stdout.strip_suffix(b"\n").unwrap_or(stdout).is_empty() {
        return Ok(None);
    }

    Ok(hydrate(plan, stdout)
        .map_err(decode_error(IN_CLIENT))?
        .into_iter()
        .next())
}

/// The session one client is attached to, in one round trip.
pub(crate) async fn client_session(
    core: &Core,
    client: &OsStr,
) -> Result<Option<SessionInfo>, Error> {
    let version = core.capabilities().await?.tmux_version().clone();
    let plan = FormatPlan::for_profile(ListProfile::Sessions, &version);

    in_client_context(core, client, &plan, hydrate_session_infos_from_stdout).await
}

/// The current window of the session one client is attached to.
pub(crate) async fn client_window(
    core: &Core,
    client: &OsStr,
) -> Result<Option<WindowProjection>, Error> {
    let version = core.capabilities().await?.tmux_version().clone();
    let plan = window_projection_plan(&version).map_err(decode_error(IN_CLIENT))?;

    in_client_context(core, client, &plan, |plan, stdout| {
        hydrate_window_projections_from_stdout(core.configuration().identity(), plan, stdout)
    })
    .await
}

/// The active pane of that window.
pub(crate) async fn client_pane(
    core: &Core,
    client: &OsStr,
) -> Result<Option<PaneProjection>, Error> {
    let version = core.capabilities().await?.tmux_version().clone();
    let plan = pane_projection_plan(&version).map_err(decode_error(IN_CLIENT))?;

    in_client_context(core, client, &plan, |plan, stdout| {
        hydrate_pane_projections_from_stdout(core.configuration().identity(), plan, stdout)
    })
    .await
}

/// Run a creating command that prints its new object, and hydrate it.
///
/// tmux's `-P -F` prints the created object through the same format machinery
/// as a listing, so creation costs one round trip rather than a create
/// followed by a lookup.
async fn create_one<T>(
    core: &Core,
    command_name: &'static str,
    build: impl FnOnce(&str) -> Command,
    template: &str,
    hydrate: impl FnOnce(&[u8]) -> Result<Vec<T>, Error>,
) -> Result<T, Error> {
    // The builder places `-P -F` itself, because tmux stops parsing flags at
    // the first positional and these commands end with a shell command.
    let command = build(template);
    let target = command.target().map(OsStr::to_os_string);
    let result = core.execute(command).await?;
    if !result.success() {
        return Err(Error::from_refused_result(
            command_name,
            &result,
            target.as_deref(),
        ));
    }
    // tmux can exit 0 having done nothing: `-S <dir>/missing/sock` prints
    // `error creating ... (No such file or directory)` on stderr and exits
    // 0 with empty stdout, though not every build writes that line -- an
    // empty stdout alone already means nothing was created. Either way this
    // is a plain refusal, not a partial effect, and tmux's own reason (when
    // it gave one) is worth more than the generic message below.
    if result.stdout().is_empty() {
        let stderr = result.stderr_lossy();
        return Err(Error::NoEffect {
            command: command_name,
            stderr: if stderr.trim().is_empty() {
                "tmux gave no reason".to_owned()
            } else {
                stderr.into_owned()
            },
        });
    }

    hydrate(result.stdout())
        .map_err(|error| error.after_effect(command_name))?
        .into_iter()
        .next()
        .ok_or_else(|| {
            Error::CommandFailed {
                command: command_name,
                exit_code: result.exit_code(),
                stderr: String::from("tmux printed no object for a creating command"),
            }
            .after_effect(command_name)
        })
}

/// Create one session and return its hydrated snapshot.
pub(crate) async fn create_session(
    core: &Core,
    build: impl FnOnce(&str) -> Command,
) -> Result<SessionInfo, Error> {
    let version = core.capabilities().await?.tmux_version().clone();
    let plan = FormatPlan::for_profile(ListProfile::Sessions, &version);
    let template = plan.template().to_owned();

    create_one(core, "new-session", build, &template, |stdout| {
        hydrate_session_infos_from_stdout(&plan, stdout).map_err(decode_error("new-session"))
    })
    .await
}

/// Create one window and return its hydrated projection.
pub(crate) async fn create_window(
    core: &Core,
    build: impl FnOnce(&str) -> Command,
) -> Result<WindowProjection, Error> {
    let version = core.capabilities().await?.tmux_version().clone();
    let plan = window_projection_plan(&version).map_err(decode_error("new-window"))?;
    let template = plan.template().to_owned();
    let identity = core.configuration().identity();

    create_one(core, "new-window", build, &template, |stdout| {
        hydrate_window_projections_from_stdout(identity, &plan, stdout)
            .map_err(decode_error("new-window"))
    })
    .await
}

/// Create one pane and return its hydrated projection.
pub(crate) async fn create_pane(
    core: &Core,
    build: impl FnOnce(&str) -> Command,
) -> Result<PaneProjection, Error> {
    let version = core.capabilities().await?.tmux_version().clone();
    let plan = pane_projection_plan(&version).map_err(decode_error("split-window"))?;
    let template = plan.template().to_owned();
    let identity = core.configuration().identity();

    create_one(core, "split-window", build, &template, |stdout| {
        hydrate_pane_projections_from_stdout(identity, &plan, stdout)
            .map_err(decode_error("split-window"))
    })
    .await
}

/// Run a mutation that returns nothing, requiring tmux to accept it.
pub(crate) async fn mutate(
    core: &Core,
    command_name: &'static str,
    command: Command,
) -> Result<(), Error> {
    let target = command.target().map(OsStr::to_os_string);
    let result = core.execute(command).await?;
    if result.success() {
        return Ok(());
    }

    Err(mutation_failure(command_name, &result, target.as_deref()))
}

pub(crate) fn mutation_failure(
    command_name: &'static str,
    result: &crate::CommandResult,
    target: Option<&OsStr>,
) -> Error {
    Error::from_refused_result(command_name, result, target)
}

#[cfg(test)]
mod tests {
    use std::os::unix::process::ExitStatusExt as _;
    use std::process::ExitStatus;
    use std::sync::Arc;
    use std::sync::atomic::{AtomicUsize, Ordering};

    use super::{client_session, create_session, mutation_failure};
    use crate::command::{CommandRequest, CommandResult, ProcessStatus, RequestId};
    use crate::formats::{FIELD_SEPARATOR, FormatPlan, ListProfile};
    use crate::internal::core::Core;
    use crate::internal::executor::{DispatchFuture, Executor, ShutdownFuture};
    use crate::{Command, Error, ErrorKind};

    struct CreationExecutor {
        calls: AtomicUsize,
        stdout: &'static [u8],
    }

    impl Executor for CreationExecutor {
        fn execute(&self, request: CommandRequest) -> DispatchFuture {
            let call = self.calls.fetch_add(1, Ordering::SeqCst);
            let stdout = if call == 0 {
                b"tmux 3.7b\n".to_vec()
            } else {
                assert_eq!(call, 1, "one probe and one creating command");
                self.stdout.to_vec()
            };
            DispatchFuture::new(async move {
                Ok(CommandResult::new(
                    request.request_id(),
                    request.summary().clone(),
                    ProcessStatus::from_exit_status(ExitStatus::from_raw(0)),
                    stdout,
                    Vec::new(),
                ))
            })
        }

        fn shutdown(&self) -> ShutdownFuture {
            ShutdownFuture::new(async { Ok(()) })
        }
    }

    /// Records the commands a lookup dispatches, answering the version probe.
    struct CapturingExecutor {
        commands: std::sync::Mutex<Vec<String>>,
    }

    impl Executor for CapturingExecutor {
        fn execute(&self, request: CommandRequest) -> DispatchFuture {
            // `CommandSummary` truncates each argument at `MAX_DIAGNOSTIC_BYTES`
            // for safe display; a sessions template has nine fields and runs
            // past that, so the diagnostic view would hide most separators.
            // `argv()` is the untruncated argv tmux actually receives.
            let summary = format!("{:?}", request.argv());
            let probe = summary.contains("display-message") || summary.contains("list-");
            self.commands
                .lock()
                .expect("the capture lock")
                .push(summary);
            let stdout = if probe {
                Vec::new()
            } else {
                b"tmux 3.7b\n".to_vec()
            };
            DispatchFuture::new(async move {
                Ok(CommandResult::new(
                    request.request_id(),
                    request.summary().clone(),
                    ProcessStatus::from_exit_status(ExitStatus::from_raw(0)),
                    stdout,
                    Vec::new(),
                ))
            })
        }

        fn shutdown(&self) -> ShutdownFuture {
            ShutdownFuture::new(async { Ok(()) })
        }
    }

    /// Apple's `strftime` rule for a conversion it does not define.
    ///
    /// `stdtime/FreeBSD/strftime.c` reaches `default: break;` and then writes
    /// `*pt++ = *format`, which is the conversion character alone: the `%` was
    /// consumed to detect the conversion and is never emitted. glibc writes
    /// both characters, which is exactly why this cannot be observed on Linux
    /// -- and macOS tests do not run on a pull request, so a live test could
    /// not catch it either. `%%` is defined, and yields one `%`.
    fn darwin_strftime(template: &str) -> String {
        let mut out = String::new();
        let mut rest = template.chars();
        while let Some(character) = rest.next() {
            if character != '%' {
                out.push(character);
                continue;
            }
            match rest.next() {
                // `%%` is the one conversion this template means to use.
                Some('%') => out.push('%'),
                // Undefined: the conversion character survives, the `%` does not.
                Some(undefined) => out.push(undefined),
                None => {}
            }
        }
        out
    }

    /// A client lookup's template must reach tmux's format parser intact.
    ///
    /// `display-message` expands through `strftime` first -- tmux calls
    /// `format_expand_time` where every listing calls `format_expand` -- and a
    /// format plan separates its fields with `%`. So the separators are
    /// conversions as far as `strftime` is concerned, and on Apple's libc they
    /// are deleted, leaving one unparseable field and a `DecodeListing` for
    /// every attached client.
    #[tokio::test]
    async fn a_client_lookup_template_survives_darwin_strftime() {
        let executor = Arc::new(CapturingExecutor {
            commands: std::sync::Mutex::new(Vec::new()),
        });
        let core = Core::from_executor_for_test(executor.clone());

        // An empty answer is "attached to nothing", which is a clean `None`
        // and leaves the dispatched template to inspect.
        let _ = client_session(&core, std::ffi::OsStr::new("/dev/pts/0")).await;

        let commands = executor.commands.lock().expect("the capture lock").clone();
        let dispatched = commands
            .iter()
            .find(|command| command.contains("#{"))
            .expect("a lookup dispatches a format template");

        // What tmux time-expands is only a problem for a command that time
        // expands. A lookup that avoids one has nothing to preserve.
        if !dispatched.contains("display-message") {
            return;
        }

        let field_separator = FIELD_SEPARATOR as char;
        let expected = FormatPlan::for_profile(
            ListProfile::Sessions,
            core.capabilities().await.expect("a version").tmux_version(),
        );
        let wanted = expected.template().matches(field_separator).count();
        assert!(wanted > 0, "a sessions template separates its fields");

        // The strftime pass is skipped whenever the template holds no `%`
        // (`format.c`'s `strchr(fmt, '%') != NULL` guard), on every libc.
        assert!(
            !dispatched.contains('%'),
            "a lookup template must contain no `%`; sent {dispatched}",
        );

        let survived = darwin_strftime(dispatched).matches(field_separator).count();
        assert_eq!(
            survived, wanted,
            "every field separator has to survive strftime; sent {dispatched}",
        );
    }

    #[test]
    fn sensitive_mutation_failure_withholds_tmux_output() {
        let secret = "sentinel-mutation-secret";
        let command = Command::new("set-option")
            .arg("--")
            .arg("mouse")
            .sensitive_arg(secret);
        let result = CommandResult::new(
            RequestId::new(1),
            command.summary(),
            ProcessStatus::from_exit_status(ExitStatus::from_raw(1 << 8)),
            Vec::new(),
            format!("bad value: {secret}\n").into_bytes(),
        );

        let error = mutation_failure("set-option", &result, None);
        assert!(matches!(&error, Error::CommandFailed { .. }));
        let diagnostic = format!("{error:?} {error}");
        assert!(!diagnostic.contains(secret), "{diagnostic}");
    }

    #[tokio::test]
    async fn successful_creation_marks_decode_and_missing_object_failures() {
        let executor = Arc::new(CreationExecutor {
            calls: AtomicUsize::new(0),
            stdout: b"malformed\n".as_slice(),
        });
        let core = Core::from_executor_for_test(executor.clone());

        let error = create_session(&core, |_format| Command::new("new-session"))
            .await
            .expect_err("tmux succeeded but did not describe the created session");

        assert_eq!(executor.calls.load(Ordering::SeqCst), 2);
        assert_eq!(error.kind(), ErrorKind::PartialEffect);
        assert!(matches!(
            error,
            Error::AfterEffect {
                operation: "new-session",
                ..
            }
        ));
    }

    /// Output tmux could not decode is a partial effect: something was made and
    /// this cannot say what. No output at all is not, and the difference is not
    /// cosmetic -- a caller told an effect may be outstanding cannot safely
    /// retry. A creating command that worked always prints the object it made,
    /// so nothing printed means nothing made, which is what every tmux does for
    /// a socket path under a directory that does not exist.
    #[tokio::test]
    async fn creation_that_printed_nothing_is_a_refusal_not_a_partial_effect() {
        let executor = Arc::new(CreationExecutor {
            calls: AtomicUsize::new(0),
            stdout: b"".as_slice(),
        });
        let core = Core::from_executor_for_test(executor.clone());

        let error = create_session(&core, |_format| Command::new("new-session"))
            .await
            .expect_err("tmux succeeded but described no session");

        assert_ne!(error.kind(), ErrorKind::PartialEffect);
        assert!(matches!(
            error,
            Error::NoEffect {
                command: "new-session",
                ..
            }
        ));
    }
}