mirror of
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e7d86d8c3a
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Make sure `flagValue.String()` can be called even when flagValue is
created by `reflect.New`
```go
import (
"flag"
"log"
"go.opentelemetry.io/collector/featuregate"
)
func main() {
fs := new(flag.FlagSet)
featuregate.GlobalRegistry().RegisterFlags(fs)
if err := fs.Parse([]string{"--help"}); err != nil {
log.Fatalf("failed to parse flags: %v", err)
}
}
```
Before this PR
```
Usage:
-feature-gates value
Comma-delimited list of feature gate identifiers. Prefix with '-' to disable the feature. '+' or no prefix will enable the feature.
panic calling String method on zero featuregate.flagValue for flag feature-gates: runtime error: invalid memory address or nil pointer dereference
failed to parse flags: flag: help requested
```
Note that there is a panic in the message.
After this PR
```
Usage:
-feature-gates value
Comma-delimited list of feature gate identifiers. Prefix with '-' to disable the feature. '+' or no prefix will enable the feature.
failed to parse flags: flag: help requested
```
---------
Co-authored-by: Yang Song <[email protected]>
72 lines
1.7 KiB
Go
72 lines
1.7 KiB
Go
// Copyright The OpenTelemetry Authors
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// SPDX-License-Identifier: Apache-2.0
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package featuregate // import "go.opentelemetry.io/collector/featuregate"
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import (
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"flag"
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"strings"
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"go.uber.org/multierr"
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)
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const (
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featureGatesFlag = "feature-gates"
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featureGatesFlagDescription = "Comma-delimited list of feature gate identifiers. Prefix with '-' to disable the feature. '+' or no prefix will enable the feature."
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)
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// RegisterFlagsOption is an option for RegisterFlags.
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type RegisterFlagsOption interface {
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private()
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}
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// RegisterFlags that directly applies feature gate statuses to a Registry.
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func (r *Registry) RegisterFlags(flagSet *flag.FlagSet, _ ...RegisterFlagsOption) {
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flagSet.Var(&flagValue{reg: r}, featureGatesFlag, featureGatesFlagDescription)
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}
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// flagValue implements the flag.Value interface and directly applies feature gate statuses to a Registry.
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type flagValue struct {
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reg *Registry
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}
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func (f *flagValue) String() string {
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// This function can be called by isZeroValue https://github.com/golang/go/blob/go1.23.3/src/flag/flag.go#L630
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// which creates an instance of flagValue using reflect.New. In this case, the field `reg` is nil.
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if f.reg == nil {
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return ""
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}
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var ids []string
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f.reg.VisitAll(func(g *Gate) {
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id := g.ID()
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if !g.IsEnabled() {
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id = "-" + id
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}
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ids = append(ids, id)
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})
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return strings.Join(ids, ",")
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}
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func (f *flagValue) Set(s string) error {
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if s == "" {
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return nil
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}
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var errs error
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ids := strings.Split(s, ",")
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for i := range ids {
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id := ids[i]
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val := true
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switch id[0] {
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case '-':
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id = id[1:]
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val = false
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case '+':
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id = id[1:]
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}
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errs = multierr.Append(errs, f.reg.Set(id, val))
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}
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return errs
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}
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