Support hooks on embed:"" fields
#493
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Relates to 840220c (alecthomas#90) This change adds support for hooks to be called on fields that are tagged with `embed:""`. ### Use case If a command has several subcommands, many (but not all) of which need the same external resource, this allows defining the flag-level inputs for that resource centrally, and then using `embed:""` in any command that needs that resource. For example, imagine: ```go type githubClientProvider struct { Token string `name:"github-token" env:"GITHUB_TOKEN"` URL string `name:"github-url" env:"GITHUB_URL"` } func (g *githubClientProvider) BeforeApply(kctx *kong.Context) error { return kctx.BindToProvider(func() (*github.Client, error) { return github.NewClient(...), nil }) } ``` Then, any command that needs GitHub client will add this field, any other resource providers it needs, and add parameters to its `Run` method to accept those resources: ```go type listUsersCmd struct { GitHub githubClientProvider `embed:""` S3 s3ClientProvider `embed:""` } func (l *listUsersCmd) Run(gh *github.Client, s3 *s3.Client) error { ... } ``` ### Alternatives It is possible to do the same today if the `*Provider` struct above is actually a Go embed instead of a Kong embed, *and* it is exported. ``` type GitHubClientProvider struct{ ... } type listUsersCmd struct { GithubClientProvider S3ClientProvider } ``` The difference is whether the struct defining the flags is required to be exported or not.
alecthomas
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abhinav
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Follow up to alecthomas#493 and 840220c Kong currently supports hooks on embedded fields of a parsed node, but only at the first level of embedding: ``` type mainCmd struct { FooOptions } type FooOptions struct { BarOptions } func (f *FooOptions) BeforeApply() error { // this will be called } type BarOptions struct { } func (b *BarOptions) BeforeApply() error { // this will not be called } ``` This change adds support for hooks to be defined on embedded fields of embedded fields so that the above example would work as expected. Per alecthomas#493, the definition of "embedded" field is adjusted to mean: - Any anonymous (Go-embedded) field that is exported - Any non-anonymous field that is tagged with `embed:""` *Testing*: Includes a test case for embedding an anonymous field in an `embed:""` and an `embed:""` field in an anonymous field.
alecthomas
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* hooks: Recursively search embedded fields for methods Follow up to #493 and 840220c Kong currently supports hooks on embedded fields of a parsed node, but only at the first level of embedding: ``` type mainCmd struct { FooOptions } type FooOptions struct { BarOptions } func (f *FooOptions) BeforeApply() error { // this will be called } type BarOptions struct { } func (b *BarOptions) BeforeApply() error { // this will not be called } ``` This change adds support for hooks to be defined on embedded fields of embedded fields so that the above example would work as expected. Per #493, the definition of "embedded" field is adjusted to mean: - Any anonymous (Go-embedded) field that is exported - Any non-anonymous field that is tagged with `embed:""` *Testing*: Includes a test case for embedding an anonymous field in an `embed:""` and an `embed:""` field in an anonymous field. * Use recursion to build up the list of receivers The 'receivers' parameter helps avoid constant memory allocation as the backing storage for the slice is reused across recursive calls.
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(I realize that I opened this without discussing the feature first,
so if you don't think this feature makes sense, feel free to close this PR.
I've tried to outline the reasoning below.)
Relates to 840220c (#90)
This change adds support for hooks to be called on fields
that are tagged with
embed:"".Use case
If a command has several subcommands,
many (but not all) of which need the same external resource,
this allows defining the flag-level inputs for that resource centrally,
allowing subcommands to declare their dependency on these resources
and use them in their
Runin a highly composible manner.For example, imagine:
Then, any command that needs GitHub client will add this field,
any other resource providers it needs,
and add parameters to its
Runmethod to accept those resources:Alternatives
It is possible to do the same today if the
*Providerstruct aboveis actually a Go embed instead of a Kong embed, and it is exported.
The difference is whether the struct defining the flags
is required to be exported or not.