diff --git a/pkg/eval/builtin_fn_flow.go b/pkg/eval/builtin_fn_flow.go index 93d2d343..e47908f1 100644 --- a/pkg/eval/builtin_fn_flow.go +++ b/pkg/eval/builtin_fn_flow.go @@ -2,6 +2,7 @@ package eval import ( "sync" + "sync/atomic" "src.elv.sh/pkg/diag" "src.elv.sh/pkg/eval/vals" @@ -136,10 +137,15 @@ func each(fm *Frame, f Callable, inputs Inputs) error { //elvdoc:fn peach // // ```elvish -// peach $f $input-list? +// peach $f~ $input-list? // ``` // -// Call `$f` on all inputs, possibly in parallel. +// Call `$f~` on all inputs, possibly in parallel. The exception from a +// [`break`](./builtin.html#break) command it will cause `peach` to stop starting new instances of +// `$f` with any remaining inputs. Because each instance of `$f~` is being run in parallel it is not +// predictable when the early termination will occur or even that it will happen before all the +// input has been consumed. The exception from a [`continue`](./builtin.html#continue) command is +// ignored. // // Example (your output will differ): // @@ -151,6 +157,12 @@ func each(fm *Frame, f Callable, inputs Inputs) error { // ▶ 16 // ▶ 15 // ▶ 14 +// ~> var tot = 0 +// ~> range 1 101 | +// peach [x]{ if (== 50 $x) { break } else { put $x } } | +// each [x]{ set tot = (+ $tot $x) } +// ~> put $tot # without the break the total should be (num 5050) +// ▶ (num 1603) // ``` // // This command is intended for homogeneous processing of possibly unbound data. If @@ -161,10 +173,11 @@ func each(fm *Frame, f Callable, inputs Inputs) error { func peach(fm *Frame, f Callable, inputs Inputs) error { var wg sync.WaitGroup - broken := false + var broken atomic.Value + broken.Store(false) var err error inputs(func(v interface{}) { - if broken || err != nil { + if broken.Load().(bool) || err != nil { return } wg.Add(1) @@ -179,9 +192,9 @@ func peach(fm *Frame, f Callable, inputs Inputs) error { case nil, Continue: // nop case Break: - broken = true + broken.Store(true) default: - broken = true + broken.Store(true) err = diag.Errors(err, ex) } } diff --git a/pkg/eval/builtin_fn_flow_test.go b/pkg/eval/builtin_fn_flow_test.go index b89ccfb5..3df0568f 100644 --- a/pkg/eval/builtin_fn_flow_test.go +++ b/pkg/eval/builtin_fn_flow_test.go @@ -30,7 +30,42 @@ func TestEach(t *testing.T) { ) } -// TODO: test peach +func TestPeach(t *testing.T) { + // Testing the `peach` builtin is a challenge since, by definition, the order of execution is + // undefined. + Test(t, + // Verify the output has the expected values when sorted. + That(`range 5 | peach [x]{ + 1 $x } | to-lines | order`). + Puts("1", "2", "3", "4", "5"), + // Verify that successive runs produce the output in different order. This test can + // theoretically suffer false positives but the vast majority of the time this will produce + // the expected output in the first iteration. The probability it will produce the same + // order of output in 100 iterations is effectively zero. + That(` + var cpu-count = 99 + var x = [(range $cpu-count | peach [x]{ + 1 $x })] + for r [(range 100)] { + var y = [(range $cpu-count | peach [x]{ sleep 1us; + 1 $x })] + if (not-eq $x $y) { + put $true + break + } + } + `).Puts(true), + // Verify that exceptions are propagated. + That(`peach [x]{ fail $x } [a]`). + Throws(FailError{"a"}, "fail $x ", "peach [x]{ fail $x } [a]"), + // Verify that `break` works by terminating the `peach` before the entire sequence is + // consumed. + That(` + var tot = 0 + range 1 101 | + peach [x]{ if (== 50 $x) { break } else { put $x } } | + each [x]{ set tot = (+ $tot $x) } + if (< $tot (/ (* 100 101) 2)) { put okay } + `).Puts("okay"), + ) +} func TestFail(t *testing.T) { Test(t, diff --git a/website/ref/language.md b/website/ref/language.md index 107d1f99..e8923708 100644 --- a/website/ref/language.md +++ b/website/ref/language.md @@ -2090,9 +2090,9 @@ If an external command exits with a non-zero status, Elvish treats that as an exception. Flow commands -- `break`, `continue` and `return` -- are ordinary builtin -commands that raise special "flow control" exceptions. The `for` and `while` -commands capture `break` and `continue`, while `fn` modifies its closure to -capture `return`. +commands that raise special "flow control" exceptions. The `for`, `while`, and +`peach` commands capture `break` and `continue`, while `fn` modifies its closure +to capture `return`. One interesting implication is that since flow commands are just ordinary commands you can build functions on top of them. For instance, this function