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feat: Implement a two-phase init which allows us to write normal init scripts (#168)

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Implement a two-phase init procedure in starship. The first phase causes the shell to source a subshell, while the second phase (in the subshell) prints the main init script.

This allows us to have nice init scripts with good styling, comments, and no pile of semicolons. Even better, it works as a drop-in replacement, so we don't need to update the docs.
This commit is contained in:
Kevin Song 2019-08-19 18:44:53 -07:00 committed by GitHub
parent 2e39c6d0fa
commit 0e82c19f37
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 166 additions and 107 deletions
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260
src/init.rs
View File

@ -1,26 +1,39 @@
use std::ffi::OsStr; use std::ffi::OsStr;
use std::path::Path; use std::path::Path;
/* We need to send execution time to the prompt for the cmd_duration module. For fish, /* We use a two-phase init here: the first phase gives a simple command to the
this is fairly straightforward. For bash and zsh, we'll need to use several shell. This command evaluates a more complicated script using `source` and
shell utilities to get the time, as well as render the prompt */ process substitution.
pub fn init(shell_name: &str) { Directly using `eval` on a shell script causes it to be evaluated in
a single line, which sucks because things like comments will comment out the
rest of the script, and you have to spam semicolons everywhere. By using
source and process substitutions, we make it possible to comment and debug
the init scripts. */
/* This prints the setup stub, the short piece of code which sets up the main
init code. The stub produces the main init script, then evaluates it with
`source` and process substitution */
pub fn init_stub(shell_name: &str) {
log::debug!("Shell name: {}", shell_name); log::debug!("Shell name: {}", shell_name);
let shell_basename = Path::new(shell_name).file_stem().and_then(OsStr::to_str); let shell_basename = Path::new(shell_name).file_stem().and_then(OsStr::to_str);
let setup_script = match shell_basename { let setup_stub = match shell_basename {
Some("bash") => { Some("bash") => {
let script = BASH_INIT; /* This *should* look like the zsh function, but bash 3.2 (MacOS default shell)
does not support using source with process substitution, so we use this
workaround from https://stackoverflow.com/a/32596626 */
let script = "source /dev/stdin <<<\"$(starship init bash --print-full-init)\"";
Some(script) Some(script)
} }
Some("zsh") => { Some("zsh") => {
let script = ZSH_INIT; let script = "source <(starship init zsh --print-full-init)";
Some(script) Some(script)
} }
Some("fish") => { Some("fish") => {
let script = FISH_INIT; // Fish does process substitution with pipes and psub instead of bash syntax
let script = "source (starship init fish --print-full-init | psub)";
Some(script) Some(script)
} }
None => { None => {
@ -46,142 +59,179 @@ pub fn init(shell_name: &str) {
None None
} }
}; };
if let Some(script) = setup_stub {
if let Some(script) = setup_script {
print!("{}", script); print!("{}", script);
} };
} }
/* /* This function (called when `--print-full-init` is passed to `starship init`)
For bash: we need to manually hook functions ourself: PROMPT_COMMAND will exec prints out the main initialization script */
right before the prompt is drawn, and any function trapped by DEBUG will exec pub fn init_main(shell_name: &str) {
before a command is run. let setup_script = match shell_name {
"bash" => Some(BASH_INIT),
"zsh" => Some(ZSH_INIT),
"fish" => Some(FISH_INIT),
_ => {
println!(
"printf \"Shell name detection failed on phase two init.\\n\
This probably indicates a bug within starship: please open\\n\
an issue at https://github.com/starship/starship/issues/new\\n\""
);
None
}
};
if let Some(script) = setup_script {
print!("{}", script);
};
}
There is a preexec/precmd framework for bash out there: if we find the /* GENERAL INIT SCRIPT NOTES
appropriate variables set, assume we are using that framework:
https://github.com/rcaloras/bash-preexec
Bash quirk: DEBUG is triggered whenever a command is executed, even if that Each init script will be passed as-is. Global notes for init scripts are in this
command is part of a pipeline. To avoid only timing the last part of a pipeline, comment, with additional per-script comments in the strings themselves.
we only start the timer if no timer has been started since the last prompt draw,
tracked by the variable PREEXEC_READY. Similarly, only draw timing info if
STARSHIP_START_TIME is defined, in case preexec was interrupted.
Finally, to work around existing DEBUG traps in the absence of a preexec-like, JOBS: The argument to `--jobs` is quoted because MacOS's `wc` leaves whitespace
we parse out the name of the old DEBUG hook, then make a new function which in the output. We pass it to starship and do the whitespace removal in Rust,
calls both that function and our starship hooks. We don't do this for to avoid the cost of an additional shell fork every shell draw.
PROMPT_COMMAND because that would probably result in two prompts.
We need to quote the output of `$(jobs -p | wc -l)` since MacOS `wc` leaves
giant spaces in front of the number (e.g. " 3"), which messes up the
word-splitting. Instead, quote the whole thing, then let Rust do the whitespace
trimming within the jobs module
*/ */
/* /* BASH INIT SCRIPT
Note to programmers: this and the zsh init will be evaluated on a single line.
Use semicolons, avoid comments, and generally think like all newlines will be We use PROMPT_COMMAND and the DEBUG trap to generate timing information. We try
deleted. to avoid clobbering what we can, and try to give the user ways around our
clobbers, if it's unavoidable.
A bash quirk is that the DEBUG trap is fired every time a command runs, even
if it's later on in the pipeline. If uncorrected, this could cause bad timing
data for commands like `slow | slow | fast`, since the timer starts at the start
of the "fast" command.
To solve this, we set a flag `PREEXEC_READY` when the prompt is drawn, and only
start the timer if this flag is present. That way, timing is for the entire command,
and not just a portion of it
*/ */
const BASH_INIT: &str = r##" const BASH_INIT: &str = r##"
# Will be run before *every* command (even ones in pipes!)
starship_preexec() { starship_preexec() {
# Avoid restarting the timer for commands in the same pipeline
if [ "$PREEXEC_READY" = "true" ]; then if [ "$PREEXEC_READY" = "true" ]; then
PREEXEC_READY=false; PREEXEC_READY=false
STARSHIP_START_TIME=$(date +%s); STARSHIP_START_TIME=$(date +%s)
fi fi
}; }
# Will be run before the prompt is drawn
starship_precmd() { starship_precmd() {
STATUS=$?; # Save the status, because commands in this pipeline will change $?
export STARSHIP_SHELL="bash"; STATUS=$?
"${starship_precmd_user_func-:}";
# Run the bash precmd function, if it's set. If not set, evaluates to no-op
"${starship_precmd_user_func-:}"
# Prepare the timer data, if needed.
if [[ $STARSHIP_START_TIME ]]; then if [[ $STARSHIP_START_TIME ]]; then
STARSHIP_END_TIME=$(date +%s); STARSHIP_END_TIME=$(date +%s)
STARSHIP_DURATION=$((STARSHIP_END_TIME - STARSHIP_START_TIME)); STARSHIP_DURATION=$((STARSHIP_END_TIME - STARSHIP_START_TIME))
PS1="$(starship prompt --status=$STATUS --jobs="$(jobs -p | wc -l)" --cmd-duration=$STARSHIP_DURATION)"; PS1="$(starship prompt --status=$STATUS --jobs="$(jobs -p | wc -l)" --cmd-duration=$STARSHIP_DURATION)"
unset STARSHIP_START_TIME; unset STARSHIP_START_TIME
else else
PS1="$(starship prompt --status=$STATUS --jobs="$(jobs -p | wc -l)")"; PS1="$(starship prompt --status=$STATUS --jobs="$(jobs -p | wc -l)")"
fi; fi
PREEXEC_READY=true; PREEXEC_READY=true; # Signal that we can safely restart the timer
}; }
# If the user appears to be using https://github.com/rcaloras/bash-preexec,
# then hook our functions into their framework.
if [[ $preexec_functions ]]; then if [[ $preexec_functions ]]; then
preexec_functions+=(starship_preexec); preexec_functions+=(starship_preexec)
precmd_functions+=(starship_precmd); precmd_functions+=(starship_precmd)
STARSHIP_START_TIME=$(date +%s);
else else
dbg_trap="$(trap -p DEBUG | cut -d' ' -f3 | tr -d \')"; # We want to avoid destroying an existing DEBUG hook. If we detect one, create
# a new function that runs both the existing function AND our function, then
# re-trap DEBUG to use this new function. This prevents a trap clobber.
dbg_trap="$(trap -p DEBUG | cut -d' ' -f3 | tr -d \')"
if [[ -z "$dbg_trap" ]]; then if [[ -z "$dbg_trap" ]]; then
trap starship_preexec DEBUG; trap starship_preexec DEBUG
elif [[ "$dbg_trap" != "starship_preexec" && "$dbg_trap" != "starship_preexec_all" ]]; then elif [[ "$dbg_trap" != "starship_preexec" && "$dbg_trap" != "starship_preexec_all" ]]; then
function starship_preexec_all(){ function starship_preexec_all(){
$dbg_trap; starship_preexec; $dbg_trap; starship_preexec
}; }
trap starship_preexec_all DEBUG; trap starship_preexec_all DEBUG
fi; fi
PROMPT_COMMAND=starship_precmd;
STARSHIP_START_TIME=$(date +%s); # Finally, prepare the precmd function and set up the start time.
fi; PROMPT_COMMAND=starship_precmd
fi
# Set up the start time and STARSHIP_SHELL, which controls shell-specific sequences
STARSHIP_START_TIME=$(date +%s)
export STARSHIP_SHELL="bash"
"##; "##;
/* For zsh: preexec_functions and precmd_functions provide preexec/precmd in a /* ZSH INIT SCRIPT
way that lets us avoid clobbering them.
Zsh quirk: preexec() is only fired if a command is actually run (unlike in ZSH has a quirk where `preexec` is only run if a command is actually run (i.e
bash, where spamming empty commands still triggers DEBUG). This means a user pressing ENTER at an empty command line will not cause preexec to fire). This
spamming ENTER at an empty command line will see increasing runtime (since can cause timing issues, as a user who presses "ENTER" without running a command
preexec never actually fires to reset the start time). will see the time to the start of the last command, which may be very large.
To fix this, only pass the time if STARSHIP_START_TIME is defined, and unset To fix this, we create STARSHIP_START_TIME upon preexec() firing, and destroy it
it after passing the time, so that we only measure actual commands. after drawing the prompt. This ensures that the timing for one command is only
ever drawn once (for the prompt immediately after it is run).
We need to quote the output of the jobs command for the same reason as
bash.
*/ */
const ZSH_INIT: &str = r##" const ZSH_INIT: &str = r##"
# Will be run before every prompt draw
starship_precmd() { starship_precmd() {
STATUS=$?; # Save the status, because commands in this pipeline will change $?
export STARSHIP_SHELL="zsh"; STATUS=$?
# Compute cmd_duration, if we have a time to consume
if [[ $STARSHIP_START_TIME ]]; then if [[ $STARSHIP_START_TIME ]]; then
STARSHIP_END_TIME="$(date +%s)"; STARSHIP_END_TIME="$(date +%s)"
STARSHIP_DURATION=$((STARSHIP_END_TIME - STARSHIP_START_TIME)); STARSHIP_DURATION=$((STARSHIP_END_TIME - STARSHIP_START_TIME))
PROMPT="$(starship prompt --status=$STATUS --cmd-duration=$STARSHIP_DURATION --jobs="$(jobs | wc -l)")"; PROMPT="$(starship prompt --status=$STATUS --cmd-duration=$STARSHIP_DURATION --jobs="$(jobs | wc -l)")"
unset STARSHIP_START_TIME; unset STARSHIP_START_TIME
else else
PROMPT="$(starship prompt --status=$STATUS --jobs="$(jobs | wc -l)")"; PROMPT="$(starship prompt --status=$STATUS --jobs="$(jobs | wc -l)")"
fi fi
}; }
starship_preexec(){ starship_preexec(){
STARSHIP_START_TIME="$(date +%s)" STARSHIP_START_TIME="$(date +%s)"
}; }
if [[ -z "${precmd_functions+1}" ]]; then
precmd_functions=() # If precmd/preexec arrays are not already set, set them. If we don't do this,
fi; # the code to detect whether starship_precmd is already in precmd_functions will
if [[ -z "${preexec_functions+1}" ]]; then # fail because the array doesn't exist (and same for starship_preexec)
preexec_functions=() [[ -z "${precmd_functions+1}" ]] && precmd_functions=()
fi; [[ -z "${preexec_functions+1}" ]] && preexec_functions=()
# If starship precmd/preexec functions are already hooked, don't double-hook them
# to avoid unnecessary performance degradation in nested shells
if [[ ${precmd_functions[(ie)starship_precmd]} -gt ${#precmd_functions} ]]; then if [[ ${precmd_functions[(ie)starship_precmd]} -gt ${#precmd_functions} ]]; then
precmd_functions+=(starship_precmd); precmd_functions+=(starship_precmd)
fi; fi
if [[ ${preexec_functions[(ie)starship_preexec]} -gt ${#preexec_functions} ]]; then if [[ ${preexec_functions[(ie)starship_preexec]} -gt ${#preexec_functions} ]]; then
preexec_functions+=(starship_preexec); preexec_functions+=(starship_preexec)
fi; fi
STARSHIP_START_TIME="$(date +%s)"; # Set up a function to redraw the prompt if the user switches vi modes
function zle-keymap-select function zle-keymap-select
{ {
PROMPT=$(starship prompt --keymap=$KEYMAP --jobs="$(jobs | wc -l)"); PROMPT=$(starship prompt --keymap=$KEYMAP --jobs="$(jobs | wc -l)")
zle reset-prompt; zle reset-prompt
}; }
zle -N zle-keymap-select;
STARSHIP_START_TIME="$(date +%s)"
zle -N zle-keymap-select
export STARSHIP_SHELL="zsh"
"##; "##;
/* Fish setup is simple because they give us CMD_DURATION. Just account for name
changes between 2.7/3.0 and do some math to convert ms->s and we can use it */
const FISH_INIT: &str = r##" const FISH_INIT: &str = r##"
function fish_prompt; function fish_prompt
set -l exit_code $status; set -l exit_code $status
set -l CMD_DURATION "$CMD_DURATION$cmd_duration"; # Account for changes in variable name between v2.7 and v3.0
set -l starship_duration (math --scale=0 "$CMD_DURATION / 1000"); set -l CMD_DURATION "$CMD_DURATION$cmd_duration"
starship prompt --status=$exit_code --cmd-duration=$starship_duration --jobs=(count (jobs -p)); set -l starship_duration (math --scale=0 "$CMD_DURATION / 1000")
end; starship prompt --status=$exit_code --cmd-duration=$starship_duration --jobs=(count (jobs -p))
end
"##; "##;

13
src/main.rs
View File

@ -58,6 +58,10 @@ fn main() {
.help("The number of currently running jobs") .help("The number of currently running jobs")
.takes_value(true); .takes_value(true);
let init_scripts_arg = Arg::with_name("print_full_init")
.long("print-full-init")
.help("Print the main initialization script (as opposed to the init stub)");
let matches = App::new("starship") let matches = App::new("starship")
.about("The cross-shell prompt for astronauts. ☄🌌️") .about("The cross-shell prompt for astronauts. ☄🌌️")
// pull the version number from Cargo.toml // pull the version number from Cargo.toml
@ -69,7 +73,8 @@ fn main() {
.subcommand( .subcommand(
SubCommand::with_name("init") SubCommand::with_name("init")
.about("Prints the shell function used to execute starship") .about("Prints the shell function used to execute starship")
.arg(&shell_arg), .arg(&shell_arg)
.arg(&init_scripts_arg),
) )
.subcommand( .subcommand(
SubCommand::with_name("prompt") SubCommand::with_name("prompt")
@ -99,7 +104,11 @@ fn main() {
match matches.subcommand() { match matches.subcommand() {
("init", Some(sub_m)) => { ("init", Some(sub_m)) => {
let shell_name = sub_m.value_of("shell").expect("Shell name missing."); let shell_name = sub_m.value_of("shell").expect("Shell name missing.");
init::init(shell_name) if sub_m.is_present("print_full_init") {
init::init_main(shell_name);
} else {
init::init_stub(shell_name);
}
} }
("prompt", Some(sub_m)) => print::prompt(sub_m.clone()), ("prompt", Some(sub_m)) => print::prompt(sub_m.clone()),
("module", Some(sub_m)) => { ("module", Some(sub_m)) => {