Fix:(issue_2225) Make external flags more robust. #2227
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Use delegation to implement the Value+Flag paradigm used for other flag types. Implement all of the Flag interfaces except Count. Borrowed heavily from flag_bool.go and flag_generic.go Add context to the error message when setting an external flag's value to its default value to avoid cryptic error messages like: `"syntax error: expected file.go:234"` And suppress the error for odd-ball external flags that report the string representation of the zero-value of some structure as the default, but do not accept that string as input. Detect such odd-balls by their `Get()` method returning `nil`.
bbadour
commented
Nov 22, 2025
| } | ||
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| func (e *extFlag) IsSet() bool { | ||
| return false |
Author
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Migrating some code from v1, I found this could be less astonishing if, instead, it were:
if e == nil || e.f == nil || e.f.Value == nil {
return false
}
return e.f.Value.String() != e.f.DefValue
Contributor
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Actually you can set a flag in the "extFlag.Set()" method and check that here.
dearchap
reviewed
Nov 22, 2025
| if e.f.DefValue != "" { | ||
| return e.Set("", e.f.DefValue) | ||
| // suppress errors for write-only external flags that always return nil | ||
| if err := e.Set("", e.f.DefValue); err != nil && e.f.Value.(flag.Getter).Get() != nil { |
Contributor
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Suggested change
| if err := e.Set("", e.f.DefValue); err != nil && e.f.Value.(flag.Getter).Get() != nil { | |
| if err := e.Set("", e.f.DefValue); err != nil { |
do you need the Get() != nil check ?
dearchap
reviewed
Nov 22, 2025
| } | ||
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| // IsDefaultVisible returns true if the flag is not hidden, otherwise false | ||
| func (e *extFlag) IsDefaultVisible() bool { |
Contributor
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is this dependent on the DefaultValue ? similar to flag library?
dearchap
reviewed
Nov 22, 2025
| } | ||
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| // RunAction executes flag action if set | ||
| func (e *extFlag) RunAction(ctx context.Context, cmd *Command) error { |
Contributor
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you dont need to define this method. interface casting will check if Flag is an ActionableFlag and call accordingly
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Use delegation to implement the Value+Flag paradigm used for other flag types.
Implement all of the Flag interfaces except Count.
Borrowed heavily from flag_bool.go and flag_generic.go
Add context to the error message when setting an external flag's value to its default value to avoid cryptic error messages like:
"syntax error: expected file.go:234"And suppress the error for odd-ball external flags that report the string representation of the zero-value of some structure as the default, but do not accept that string as input. Detect such odd-balls by their
Get()method returningnil.What type of PR is this?
What this PR does / why we need it:
Solve:
Which issue(s) this PR fixes:
Fixes #2225
Testing
Installed gfmrun and make passes. Also the same code passes the test cases for a large code base that uses the feature.
Release Notes