Struct SubshellSnapshot 

pub struct SubshellSnapshot {

    pub paramtab: HashMap<String, Param>,
    pub paramtab_hashed_storage: HashMap<String, IndexMap<String, String>>,
    pub positional_params: Vec<String>,
    pub env_vars: HashMap<String, String>,
    pub cwd: Option<PathBuf>,
    pub umask: u32,
    pub traps: HashMap<String, String>,
    pub opts: HashMap<String, bool>,
    pub aliases: Vec<(String, String)>,
    pub shfuncs: HashMap<String, Box<shfunc>>,
    pub functions_compiled: HashMap<String, Chunk>,
    pub function_source: HashMap<String, String>,
    pub modules: HashMap<String, i32>,
    pub thingytab: HashMap<String, Thingy>,
    pub keymapnamtab: HashMap<String, KeymapName>,
}

Snapshot of subshell-isolated state. Captured at ( entry, restored at ) exit. zsh subshell semantics: assignments inside (…) don’t leak to the outer scope — and that includes export. zsh forks a child for the subshell so the child’s env::set_var dies with the child; without a fork (zshrs runs subshells in-process for perf), we snapshot+restore the OS env table around the subshell. Otherwise (export y=v) would leak y to the parent shell, breaking every script that uses a subshell to scope an env override. Snapshot of mutable executor state across a subshell boundary. Port of the entersubsh() save/restore Src/exec.c does at line 1084 — captures everything that must be replaced when a (...) group fires.

Fields

paramtab: HashMap<String, Param>

Snapshot of paramtab (the C-canonical parameter store) at subshell entry. Step 1 of the unification mirrors writes to paramtab, so subshell-scoped assignments now show up there too — without this snapshot, restoring only variables / arrays / assoc_arrays leaks the subshell’s writes to the parent via paramtab (e.g. x=outer; (x=inner); echo $x returned inner because paramsubst reads through paramtab).

paramtab_hashed_storage: HashMap<String, IndexMap<String, String>>

paramtab_hashed_storage field.

positional_params: Vec<String>

positional_params field.

env_vars: HashMap<String, String>

env_vars field.

cwd: Option<PathBuf>

Process working directory at subshell entry. cd inside the subshell shouldn’t leak to the parent; we restore on End.

umask: u32

File-creation mask at subshell entry. zsh forks for (...) so umask set inside dies with the child; we run subshells in process so we must restore the mask on End. Otherwise umask 022; (umask 077); umask shows 077 in the parent.

traps: HashMap<String, String>

Parent’s traps at subshell entry. zsh’s (trap "echo X" EXIT; true) runs the trap when the subshell exits — BEFORE the parent continues. Without this snapshot, the trap inherited from parent would fire, OR a trap set inside the subshell would leak to the parent’s process exit. Restored on subshell_end after the subshell’s own EXIT trap (if any) has fired. Stores a snapshot of crate::ported::builtin::traps_table() (canonical).

opts: HashMap<String, bool>

Parent’s shell options at subshell entry. (set -e) / (setopt extendedglob) mustn’t leak; zsh forks the subshell so child options die with the child. We run in-process, so we must restore the option store on subshell_end.

aliases: Vec<(String, String)>

Parent’s alias entries at subshell entry. zsh forks for (...) so (alias x=y) inside a subshell dies with the child and doesn’t leak to the parent. zshrs runs subshells in-process, so we must restore the alias table on subshell_end. Bug #209 in docs/BUGS.md. Stored as a flat Vec<(name, text)> snapshot — the underlying alias_table holds an IndexMap<String, alias> but alias carries hashnode metadata we don’t need to round-trip; only name + text are observable via alias NAME lookup.

shfuncs: HashMap<String, Box<shfunc>>

Parent’s shell-function table at subshell entry. C zsh’s entersubsh (Src/exec.c) forks before running the subshell body so (f() { ... }) defining a function dies with the child and never leaks to the parent. zshrs runs subshells in-process, so we must clone shfunctab on entry and restore on exit. Bug #208 in docs/BUGS.md. Stored as the full HashMap<String, Box<shfunc>> clone — shfunc is Clone and the table snapshot is bounded by the user’s declared function set.

functions_compiled: HashMap<String, Chunk>

Parent’s compiled-function chunks at subshell entry. Companion to shfuncs above — ShellExecutor.functions_compiled is the runtime dispatch table that Op::CallFunction reads through; without restoring it, a subshell (g() { override; }) leaves the override bytecode chunk in place so the parent’s g call still runs the override after subshell_end restored shfunctab. Bug #208 in docs/BUGS.md.

function_source: HashMap<String, String>

Parent’s function source map at subshell entry. Companion to functions_compiled so typeset -f / whence show the parent’s source after subshell exit, not the subshell’s overridden body. Bug #208 in docs/BUGS.md.

modules: HashMap<String, i32>

Parent’s modulestab modules map at subshell entry. zsh forks for (...) so a (zmodload zsh/X) inside the subshell sets MOD_INIT_B on the child’s modulestab; when the child exits the flag dies with it and the parent’s modulestab is untouched. zshrs runs subshells in-process, so a subshell zmodload would otherwise flip the parent’s ${modules[zsh/X]} from unset to “loaded”. Snapshot here and restore on subshell_end. Bug #210 in docs/BUGS.md. Stored as (name → flags) since module struct doesn’t derive Clone (LinkList/ Linkedmod) — and the only thing zmodload mutates that affects introspection is the flags bitmask (MOD_INIT_B for loaded, MOD_UNLOAD for unloaded).

thingytab: HashMap<String, Thingy>

Parent’s THINGYTAB (ZLE widget registry) at subshell entry. zsh forks for (...) so zle -N w f / zle -D w inside the subshell flip widget bindings only in the child; when the child exits the parent’s widget table is untouched. zshrs runs subshells in-process so a subshell’s zle -D w would otherwise unbind the parent’s widget. Bug #453 in docs/BUGS.md.

keymapnamtab: HashMap<String, KeymapName>

Parent’s KEYMAPNAMTAB (named keymap registry) at subshell entry. Same fork-copy semantics as THINGYTAB — a subshell’s bindkey -N km / bindkey -D km mutates only the child’s keymap registry in C zsh. Bug #454 in docs/BUGS.md.