mirror of https://github.com/hashicorp/consul
40 lines
1.2 KiB
Markdown
40 lines
1.2 KiB
Markdown
|
# Consul `types` Package
|
||
|
|
|
||
|
|
The Go language has a strong type system built into the language. The
|
||
|
|
`types` package corrals named types into a single package that is terminal in
|
||
|
|
`go`'s import graph. The `types` package should not have any downstream
|
||
|
|
dependencies. Each subsystem that defines its own set of types exists in its
|
||
|
|
own file, but all types are defined in the same package.
|
||
|
|
|
||
|
|
# Why
|
||
|
|
|
||
|
|
> Everything should be made as simple as possible, but not simpler.
|
||
|
|
|
||
|
|
`string` is a useful container and underlying type for identifiers, however
|
||
|
|
the `string` type is effectively opaque to the compiler in terms of how a
|
||
|
|
given string is intended to be used. For instance, there is nothing
|
||
|
|
preventing the following from happening:
|
||
|
|
|
||
|
|
```go
|
||
|
|
// `map` of Widgets, looked up by ID
|
||
|
|
var widgetLookup map[string]*Widget
|
||
|
|
// ...
|
||
|
|
var widgetID string = "widgetID"
|
||
|
|
w, found := widgetLookup[widgetID]
|
||
|
|
|
||
|
|
// Bad!
|
||
|
|
var widgetName string = "name of widget"
|
||
|
|
w, found := widgetLookup[widgetName]
|
||
|
|
```
|
||
|
|
|
||
|
|
but this class of problem is entirely preventable:
|
||
|
|
|
||
|
|
```go
|
||
|
|
type WidgetID string
|
||
|
|
var widgetLookup map[WidgetID]*Widget
|
||
|
|
var widgetName
|
||
|
|
```
|
||
|
|
|
||
|
|
TL;DR: intentions and idioms aren't statically checked by compilers. The
|
||
|
|
`types` package uses Go's strong type system to prevent this class of bug.
|