c55a706513
package's ParsePackage to take prefix and updated related skip conditional. Also updated args in call to ParsePackage within server. Last paragraph of main package comment was updated, along with the second to last paragraph of readme.
78 lines
2.4 KiB
Markdown
78 lines
2.4 KiB
Markdown
# jsonenums
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jsonenums is a tool to automate the creation of methods that satisfy the
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`json.Marshaler` and `json.Unmarshaler` interfaces.
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Given the name of a (signed or unsigned) integer type T that has constants
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defined, jsonenums will create a new self-contained Go source file implementing
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```
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func (t T) MarshalJSON() ([]byte, error)
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func (t *T) UnmarshalJSON([]byte) error
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```
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The file is created in the same package and directory as the package that
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defines T. It has helpful defaults designed for use with go generate.
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jsonenums is a simple implementation of a concept and the code might not be the
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most performant or beautiful to read.
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For example, given this snippet,
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```Go
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package painkiller
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type Pill int
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const (
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Placebo Pill = iota
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Aspirin
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Ibuprofen
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Paracetamol
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Acetaminophen = Paracetamol
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)
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```
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running this command
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```
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jsonenums -type=Pill
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```
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in the same directory will create the file `pill_jsonenums.go`, in package
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`painkiller`, containing a definition of
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```
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func (r Pill) MarshalJSON() ([]byte, error)
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func (r *Pill) UnmarshalJSON([]byte) error
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```
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`MarshalJSON` will translate the value of a `Pill` constant to the `[]byte`
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representation of the respective constant name, so that the call
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`json.Marshal(painkiller.Aspirin)` will return the bytes `[]byte("\"Aspirin\"")`.
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`UnmarshalJSON` performs the opposite operation; given the `[]byte`
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representation of a `Pill` constant it will change the receiver to equal the
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corresponding constant. So given `[]byte("\"Aspirin\"")` the receiver will
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change to `Aspirin` and the returned error will be `nil`.
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Typically this process would be run using go generate, like this:
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```
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//go:generate jsonenums -type=Pill
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```
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If multiple constants have the same value, the lexically first matching name
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will be used (in the example, Acetaminophen will print as "Paracetamol").
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With no arguments, it processes the package in the current directory. Otherwise,
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the arguments must name a single directory holding a Go package or a set of Go
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source files that represent a single Go package.
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The `-type` flag accepts a comma-separated list of types so a single run can
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generate methods for multiple types. The default output file is t_jsonenums.go,
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where t is the lower-cased name of the first type listed. The suffix can be
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overridden with the `-suffix` flag and a prefix may be added with the `-prefix`
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flag.
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This is not an official Google product (experimental or otherwise), it is just code that happens to be owned by Google.
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