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feat: implement $SHLVL and $BASH_SUBSHELL #251

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feat: implement $SHLVL and $BASH_SUBSHELL #251

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32 changes: 31 additions & 1 deletion brush-core/src/shell.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -79,11 +79,17 @@ pub struct Shell {

impl Clone for Shell {
fn clone(&self) -> Self {
let mut env = self.env.clone();

if !self.options.sh_mode {
increment_level_var(&mut env, "BASH_SUBSHELL", 1, false).unwrap();
}

Self {
traps: self.traps.clone(),
open_files: self.open_files.clone(),
working_dir: self.working_dir.clone(),
env: self.env.clone(),
env,
funcs: self.funcs.clone(),
options: self.options.clone(),
jobs: jobs::JobManager::new(),
Expand Down Expand Up @@ -279,7 +285,13 @@ impl Shell {
)?;
}

increment_level_var(&mut env, "SHLVL", 1, true)?;

if !options.sh_mode {
let mut lvl = ShellVariable::new("0".into());
lvl.export();
env.set_global("BASH_SUBSHELL", lvl)?;

if let Some(shell_name) = &options.shell_name {
env.set_global("BASH", ShellVariable::new(shell_name.into()))?;
}
Expand Down Expand Up @@ -1182,3 +1194,21 @@ fn parse_string_impl(
tracing::debug!(target: trace_categories::PARSE, "Parsing string as program...");
parser.parse(true)
}

// parse a numeric variable from a string, increment it by 1, then re-export
fn increment_level_var(
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shell.rs is already, well, longer than I'd like. Could you turn this into a pub(crate) helper in variables.rs or similar?

For what it's worth, it seems more understandable to me to have the default value expressing the pre-increment default (i.e., 0 here).

env: &mut ShellEnvironment,
var: &str,
default: usize,
export: bool,
) -> Result<(), error::Error> {
let lvl = env
.get_str(var)
.and_then(|s| s.parse::<usize>().ok().map(|n| n + 1))
.unwrap_or(default);
let mut lvl = ShellVariable::new(ShellValue::String(lvl.to_string()));
if export {
lvl.export();
}
env.set_global(var, lvl)
}
34 changes: 34 additions & 0 deletions brush-shell/tests/cases/compound_cmds/subshell.yaml
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Expand Up @@ -23,3 +23,37 @@ cases:
- name: "Piped subshell usage"
stdin: |
(echo hi) | wc -l

- name: "SHLVL subshell"
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It seems like we need some tests to ensure that SHLVL will work correctly across process invocations (i.e., nested shells and not just subshells). Thoughts on how to do that? Nested invocation of $0? Call through bash in the middle?

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@reubeno I thought about it and created a test using $SHELL but is points to nowhere inside the Oracle. Now, looking at it, I learned about $0, so I will try using that instead. I'm not sure yet how interactivity works there.

$0
$0
$0 -c 'echo $SHLVL; $0'

stdin: |
initial="$SHLVL"
function rec_subshell {
if [ "$1" -ge "$2" ]; then
exit
else
(
test $initial -eq $SHLVL; echo $?
rec_subshell $(($1 + 1)) $2
)
fi
}
rec_subshell 1 10


- name: "BASH_SUBSHELL"
stdin: |
initial="$BASH_SUBSHELL"

function rec_subshell {
if [ "$1" -ge "$2" ]; then
exit
else
(
test $initial -ne $BASH_SUBSHELL; echo $?
echo $BASH_SUBSHELL
initial=$BASH_SUBSHELL
rec_subshell $(($1 + 1)) $2
)
fi
}
rec_subshell 1 10
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