Add support for omitempty field tag to exclude empty values from queries and headers
#107
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…eries and headers
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README.md
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| Page int `in:"query=page;default=1"` | ||
| PerPage int `in:"query=per_page;default=20"` | ||
| IsMember bool `in:"query=is_member"` | ||
| Search *string `in:"query=search,omitempty"` |
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The query directive is designed in the signautre as query(name1, name2, ...), here the omitempty will be read as the second name used in the query parameters. I'm thinking:
- if we should define a separate
omitemptydirective for this, i.e.in:"query=search;header=x-api-keyword;omitempty"? - shall we just use
patch.Field[T]as the field type, since it was designed for indicating absent values, i.e.Search patch.Field[string], whenSearch.Valid == false, it will be omitted from the final resource.
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Using patch.Field[T] for the field type would not be ideal for us as this would complicate using our library for consumers, if this can be handled purely by the stuct tags then this would be ideal.
I have updated it to use a new omitempty directive now. I do agree it is better.
I'm not sure on the implementation - as the new directive doesn't take any action by itself - but is used inside the existing directives - maybe this is ok, or maybe there is a better way?
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I totally agree. I hope patch.Field[T] should be used only in rare cases.
core/formencoder.go
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| type FormEncoder struct { | ||
| Setter func(key string, value []string) // form value setter | ||
| } | ||
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| func (e *FormEncoder) Execute(rtm *DirectiveRuntime) error { | ||
| tag := rtm.Resolver.Field.Tag.Get("in") | ||
| if rtm.Value.IsZero() && strings.Contains(tag, "omitempty") { |
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This test is error prone. Either check
rtm.Directive.Argvforomitemptydefined in a directive, orrtm.Resolver.GetDirectiveforomitemptydefined as a single directive
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Thank you! Have gone with option 2.
core/formencoder.go
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| type FormEncoder struct { | ||
| Setter func(key string, value []string) // form value setter | ||
| } | ||
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| func (e *FormEncoder) Execute(rtm *DirectiveRuntime) error { | ||
| if rtm.Value.IsZero() { | ||
| for _, d := range rtm.Resolver.Directives { | ||
| if d.Name == "omitempty" { |
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maybe we could use a constant here to link this back to the actual directive?
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I think it's okay. But we can use API rtm.Resolver.GetDirective("omitempty") here to simplify the code.
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thanks! missed that.
| // DirectiveOmitEmpty is used with the DirectiveQuery, DirectiveForm, and DirectiveHeader to indicate that the field | ||
| // should be omitted when the value is empty. | ||
| // It does not have any affect when used by itself | ||
| type DirectiveOmitEmpty struct{} |
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In the json package, omitempty is a tag that affects both json marshalling and unmarshalling. Since we have modified the encoding behaviour of using omitempty here, I would suggest upgrading decoding as well to have the similar effects. Otherwise, it might bring up suprises for users who expect omitempty to work in the decoding function. Have you ever considered how it should behave in decoding?
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I think that omitempty only affects Marshal with json, and not Unmarshal - as such I think it only makes sense to only modify encoding and not decoding.
Or maybe I'm missing something obvious!
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Yeah, you're right. The omitempty tag only influences the marshalling process (i.e., converting a Go struct into JSON).
Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #107 +/- ##
==========================================
- Coverage 90.78% 90.70% -0.08%
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Files 34 35 +1
Lines 1530 1539 +9
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+ Hits 1389 1396 +7
- Misses 97 99 +2
Partials 44 44
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Adds support for an
omitemptytag.Main use case is for query parameters where we may not want have empty keys
i.e.
/pets?name_pointer=By adding
omitemptyto the tag then this the key will not appear in the query stringi.e.
This will create
/petsThis has been added to the
formencoderso that it will also remove empty headers.I have picked
omitemptyas I feel this will feel most natural for engineers as they are likely already used to this syntax with JSON.