mirror of
https://github.com/go-sylixos/elvish.git
synced 2024-12-05 03:17:50 +08:00
340 lines
8.2 KiB
Go
340 lines
8.2 KiB
Go
package eval
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import (
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"sync"
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"github.com/elves/elvish/pkg/diag"
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"github.com/elves/elvish/pkg/eval/vals"
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)
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// Flow control.
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// TODO(xiaq): Document "multi-error".
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func init() {
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addBuiltinFns(map[string]interface{}{
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"run-parallel": runParallel,
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// Exception and control
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"fail": fail,
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"multi-error": multiErrorFn,
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"return": returnFn,
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"break": breakFn,
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"continue": continueFn,
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// Iterations.
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"each": each,
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"peach": peach,
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})
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}
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//elvdoc:fn run-parallel
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//
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// ```elvish
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// run-parallel $callable ...
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// ```
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//
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// Run several callables in parallel, and wait for all of them to finish.
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//
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// If one or more callables throw exceptions, the other callables continue running,
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// and a composite exception is thrown when all callables finish execution.
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//
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// The behavior of `run-parallel` is consistent with the behavior of pipelines,
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// except that it does not perform any redirections.
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//
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// Here is an example that lets you pipe the stdout and stderr of a command to two
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// different commands:
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//
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// ```elvish
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// pout = (pipe)
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// perr = (pipe)
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// run-parallel {
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// foo > $pout 2> $perr
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// pwclose $pout
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// pwclose $perr
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// } {
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// bar < $pout
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// prclose $pout
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// } {
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// bar2 < $perr
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// prclose $perr
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// }
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// ```
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//
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// This command is intended for doing a fixed number of heterogeneous things in
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// parallel. If you need homogeneous parallel processing of possibly unbound data,
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// use `peach` instead.
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//
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// @cf peach
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func runParallel(fm *Frame, functions ...Callable) error {
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var waitg sync.WaitGroup
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waitg.Add(len(functions))
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exceptions := make([]*Exception, len(functions))
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for i, function := range functions {
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go func(fm2 *Frame, function Callable, exception **Exception) {
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err := function.Call(fm2, NoArgs, NoOpts)
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if err != nil {
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*exception = err.(*Exception)
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}
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waitg.Done()
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}(fm.fork("[run-parallel function]"), function, &exceptions[i])
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}
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waitg.Wait()
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return makePipelineError(exceptions)
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}
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//elvdoc:fn each
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//
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// ```elvish
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// each $f $input-list?
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// ```
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//
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// Call `$f` on all inputs. Examples:
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//
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// ```elvish-transcript
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// ~> range 5 8 | each [x]{ ^ $x 2 }
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// ▶ 25
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// ▶ 36
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// ▶ 49
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// ~> each [x]{ put $x[:3] } [lorem ipsum]
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// ▶ lor
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// ▶ ips
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// ```
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//
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// @cf peach
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//
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// Etymology: Various languages, as `for each`. Happens to have the same name as
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// the iteration construct of
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// [Factor](http://docs.factorcode.org/content/word-each,sequences.html).
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func each(fm *Frame, f Callable, inputs Inputs) error {
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broken := false
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var err error
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inputs(func(v interface{}) {
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if broken {
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return
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}
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newFm := fm.fork("closure of each")
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ex := f.Call(newFm, []interface{}{v}, NoOpts)
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newFm.Close()
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if ex != nil {
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switch Cause(ex) {
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case nil, Continue:
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// nop
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case Break:
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broken = true
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default:
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broken = true
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err = ex
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}
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}
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})
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return err
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}
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//elvdoc:fn peach
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//
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// ```elvish
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// peach $f $input-list?
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// ```
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//
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// Call `$f` on all inputs, possibly in parallel.
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//
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// Example (your output will differ):
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//
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// ```elvish-transcript
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// ~> range 1 7 | peach [x]{ + $x 10 }
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// ▶ 12
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// ▶ 11
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// ▶ 13
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// ▶ 16
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// ▶ 15
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// ▶ 14
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// ```
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//
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// This command is intended for homogeneous processing of possibly unbound data. If
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// you need to do a fixed number of heterogeneous things in parallel, use
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// `run-parallel`.
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//
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// @cf each run-parallel
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func peach(fm *Frame, f Callable, inputs Inputs) error {
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var w sync.WaitGroup
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broken := false
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var err error
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inputs(func(v interface{}) {
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if broken || err != nil {
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return
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}
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w.Add(1)
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go func() {
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newFm := fm.fork("closure of peach")
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newFm.ports[0] = DevNullClosedChan
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ex := f.Call(newFm, []interface{}{v}, NoOpts)
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newFm.Close()
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if ex != nil {
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switch Cause(ex) {
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case nil, Continue:
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// nop
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case Break:
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broken = true
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default:
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broken = true
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err = diag.Errors(err, ex)
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}
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}
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w.Done()
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}()
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})
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w.Wait()
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return err
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}
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// FailError is an error returned by the "fail" command.
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type FailError struct{ Content interface{} }
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// Error returns the string representation of the cause.
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func (e FailError) Error() string { return vals.ToString(e.Content) }
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// Fields returns a structmap for accessing fields from Elvish.
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func (e FailError) Fields() vals.StructMap { return failFields{e} }
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type failFields struct{ e FailError }
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func (failFields) IsStructMap() {}
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func (f failFields) Type() string { return "fail" }
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func (f failFields) Content() interface{} { return f.e.Content }
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//elvdoc:fn fail
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//
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// ```elvish
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// fail $v
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// ```
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//
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// Throws an exception; `$v` may be any type. If `$v` is already an exception,
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// `fail` rethrows it.
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//
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// ```elvish-transcript
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// ~> fail bad
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// Exception: bad
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// [tty 9], line 1: fail bad
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// ~> put ?(fail bad)
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// ▶ ?(fail bad)
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// ~> fn f { fail bad }
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// ~> fail ?(f)
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// Exception: bad
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// Traceback:
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// [tty 7], line 1:
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// fn f { fail bad }
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// [tty 8], line 1:
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// fail ?(f)
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// ```
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func fail(v interface{}) error {
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if e, ok := v.(error); ok {
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// MAYBE TODO: if v is an exception, attach a "rethrown" stack trace,
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// like Java
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return e
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}
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return FailError{v}
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}
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func multiErrorFn(excs ...*Exception) error {
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return PipelineError{excs}
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}
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//elvdoc:fn return
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//
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// Raises the special "return" exception. When raised inside a named function
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// (defined by the [`fn` keyword](../language.html#function-definition-fn)) it
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// is captured by the function and causes the function to terminate. It is not
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// captured by an anonymous function (aka [lambda](../language.html#lambda)).
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//
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// Because `return` raises an exception it can be caught by a
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// [`try`](language.html#exception-control-try) block. If not caught, either
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// implicitly by a named function or explicitly, it causes a failure like any
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// other uncaught exception.
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//
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// See the discussion about [flow commands and exceptions](language.html#exception-and-flow-commands)
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//
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// **Note**: While defining a `return~ = { builtin:return }` lambda should
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// work it currently results results in infinite recursion. **Do not do
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// this!**
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//
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// **Note**: You can create a `return` function and it will shadow the builtin
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// command. **Do not do this!**. You cannot propagate the exception to the
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// calling function. In this example you might, incorrectly, expect "no" to
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// not appear in the output:
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//
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// ```elvish-transcript
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// > fn return []{ put 'return'; builtin:return; put 'should not appear' }
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// > fn test-return []{ put 'yes'; return; put 'no' }
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// > test-return
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// ▶ yes
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// ▶ return
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// ▶ no
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// ```
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func returnFn() error {
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return Return
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}
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//elvdoc:fn break
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//
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// Raises the special "break" exception. When raised inside a loop it is
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// captured and causes the loop to terminate.
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//
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// Because `break` raises an exception it can be caught by a
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// [`try`](language.html#exception-control-try) block. If not caught, either
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// implicitly by a loop or explicitly, it causes a failure like any other
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// uncaught exception.
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//
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// See the discussion about [flow commands and exceptions](language.html#exception-and-flow-commands)
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//
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// **Note**: You can create a `break` function and it will shadow the builtin
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// command. If you do so you should explicitly invoke the builtin. For example:
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//
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// ```elvish-transcript
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// > fn break []{ put 'break'; builtin:break; put 'should not appear' }
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// > for x [a b c] { put $x; break; put 'unexpected' }
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// ▶ a
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// ▶ break
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// ```
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func breakFn() error {
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return Break
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}
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//elvdoc:fn continue
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//
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// Raises the special "continue" exception. When raised inside a loop it is
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// captured and causes the loop to begin its next iteration.
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//
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// Because `continue` raises an exception it can be caught by a
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// [`try`](language.html#exception-control-try) block. If not caught, either
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// implicitly by a loop or explicitly, it causes a failure like any other
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// uncaught exception.
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//
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// See the discussion about [flow commands and exceptions](language.html#exception-and-flow-commands)
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//
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// **Note**: You can create a `continue` function and it will shadow the builtin
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// command. If you do so you should explicitly invoke the builtin. For example:
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//
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// ```elvish-transcript
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// > fn break []{ put 'continue'; builtin:continue; put 'should not appear' }
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// > for x [a b c] { put $x; continue; put 'unexpected' }
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// ▶ a
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// ▶ continue
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// ▶ b
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// ▶ continue
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// ▶ c
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// ▶ continue
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// ```
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func continueFn() error {
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return Continue
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}
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