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starlark: require go1.23 for new iterators (#551)
The correct type for new iterators is iter.Seq, which depends on a go1.23-only package, so we must limit the new functions to new toolchains. In principle this is (yet another) breaking change, but I suspect only users of (pre-)go1.23 will notice, and they are living on the bleeding edge by choice. Also, fix a couple of doc links.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,118 @@ | ||
| // Copyright 2024 The Bazel Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
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| //go:build go1.23 | ||
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| package starlark | ||
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| import ( | ||
| "fmt" | ||
| "iter" | ||
| ) | ||
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| func (d *Dict) Entries() iter.Seq2[Value, Value] { return d.ht.entries } | ||
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| // Elements returns a go1.23 iterator over the elements of the list. | ||
| // | ||
| // Example: | ||
| // | ||
| // for elem := range list.Elements() { ... } | ||
| func (l *List) Elements() iter.Seq[Value] { | ||
| return func(yield func(Value) bool) { | ||
| if !l.frozen { | ||
| l.itercount++ | ||
| defer func() { l.itercount-- }() | ||
| } | ||
| for _, x := range l.elems { | ||
| if !yield(x) { | ||
| break | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| // Elements returns a go1.23 iterator over the elements of the tuple. | ||
| // | ||
| // (A Tuple is a slice, so it is of course directly iterable. This | ||
| // method exists to provide a fast path for the [Elements] standalone | ||
| // function.) | ||
| func (t Tuple) Elements() iter.Seq[Value] { | ||
| return func(yield func(Value) bool) { | ||
| for _, x := range t { | ||
| if !yield(x) { | ||
| break | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| func (s *Set) Elements() iter.Seq[Value] { | ||
| return func(yield func(k Value) bool) { | ||
| s.ht.entries(func(k, _ Value) bool { return yield(k) }) | ||
| } | ||
| } | ||
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| // Elements returns an iterator for the elements of the iterable value. | ||
| // | ||
| // Example of go1.23 iteration: | ||
| // | ||
| // for elem := range Elements(iterable) { ... } | ||
| // | ||
| // Push iterators are provided as a convenience for Go client code. The | ||
| // core iteration behavior of Starlark for-loops is defined by the | ||
| // [Iterable] interface. | ||
| func Elements(iterable Iterable) iter.Seq[Value] { | ||
| // Use specialized push iterator if available (*List, Tuple, *Set). | ||
| type hasElements interface { | ||
| Elements() iter.Seq[Value] | ||
| } | ||
| if iterable, ok := iterable.(hasElements); ok { | ||
| return iterable.Elements() | ||
| } | ||
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| iter := iterable.Iterate() | ||
| return func(yield func(Value) bool) { | ||
| defer iter.Done() | ||
| var x Value | ||
| for iter.Next(&x) && yield(x) { | ||
| } | ||
| } | ||
| } | ||
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| // Entries returns an iterator over the entries (key/value pairs) of | ||
| // the iterable mapping. | ||
| // | ||
| // Example of go1.23 iteration: | ||
| // | ||
| // for k, v := range Entries(mapping) { ... } | ||
| // | ||
| // Push iterators are provided as a convenience for Go client code. The | ||
| // core iteration behavior of Starlark for-loops is defined by the | ||
| // [Iterable] interface. | ||
| func Entries(mapping IterableMapping) iter.Seq2[Value, Value] { | ||
| // If available (e.g. *Dict), use specialized push iterator, | ||
| // as it gets k and v in one shot. | ||
| type hasEntries interface { | ||
| Entries() iter.Seq2[Value, Value] | ||
| } | ||
| if mapping, ok := mapping.(hasEntries); ok { | ||
| return mapping.Entries() | ||
| } | ||
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| iter := mapping.Iterate() | ||
| return func(yield func(k, v Value) bool) { | ||
| defer iter.Done() | ||
| var k Value | ||
| for iter.Next(&k) { | ||
| v, found, err := mapping.Get(k) | ||
| if err != nil || !found { | ||
| panic(fmt.Sprintf("Iterate and Get are inconsistent (mapping=%v, key=%v)", | ||
| mapping.Type(), k.Type())) | ||
| } | ||
| if !yield(k, v) { | ||
| break | ||
| } | ||
| } | ||
| } | ||
| } |
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