mirror of
https://github.com/hanzoai/yaegi.git
synced 2026-10-01 00:49:47 +00:00
Marc VertesandGitHub
5ccf1b0a44
This change implements a workaround to better support composed interfaces in yaegi and let the interpreter define objects which implement multiple interfaces at once. We use the existing MapTypes to store what possible composed interface wrapper could be used for some interfaces. When generating an interface wrapper, the wrapper with the highest number of implemented methods is chosen. This is still an imperfect solution but it improves the accuracy of interpreter in some critical cases. This workaround could be removed in future if/when golang/go#15924 is resolved. Fixes #1425.
45 lines
1.1 KiB
Go
45 lines
1.1 KiB
Go
package main
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import (
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"io"
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"log"
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"os"
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"strings"
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)
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type WrappedReader struct {
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reader io.Reader
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}
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func (wr WrappedReader) Read(p []byte) (n int, err error) {
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return wr.reader.Read(p)
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}
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// Of course, this implementation is completely stupid because it does not write
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// to the intended writer, as any honest WriteTo implementation should. its
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// implemtion is just to make obvious the divergence of behaviour with yaegi.
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func (wr WrappedReader) WriteTo(w io.Writer) (n int64, err error) {
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// Ignore w, send to Stdout to prove whether this WriteTo is used.
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data, err := io.ReadAll(wr)
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if err != nil {
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return 0, err
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}
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nn, err := os.Stdout.Write(data)
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return int64(nn), err
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}
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func main() {
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f := strings.NewReader("hello world")
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wr := WrappedReader{reader: f}
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// behind the scenes, io.Copy is supposed to use wr.WriteTo if the implementation exists.
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// With Go, it works as expected, i.e. the output is sent to os.Stdout.
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// With Yaegi, it doesn't, i.e. the output is sent to io.Discard.
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if _, err := io.Copy(io.Discard, wr); err != nil {
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log.Fatal(err)
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}
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}
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// Output:
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// hello world
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