github.com/serversong/goreporter@v0.0.0-20200325104552-3cfaf44fd178/linters/interfacer/README.md (about)

     1  # interfacer
     2  
     3  [![GoDoc](https://godoc.org/github.com/mvdan/interfacer?status.svg)](https://godoc.org/github.com/mvdan/interfacer)
     4  [![Build Status](https://travis-ci.org/mvdan/interfacer.svg?branch=master)](https://travis-ci.org/mvdan/interfacer)
     5  
     6  A linter that suggests interface types. In other words, it warns about
     7  the usage of types that are more specific than necessary.
     8  
     9  	go get -u github.com/mvdan/interfacer/cmd/interfacer
    10  
    11  ### Usage
    12  
    13  ```go
    14  func ProcessInput(f *os.File) error {
    15          b, err := ioutil.ReadAll(f)
    16          if err != nil {
    17                  return err
    18          }
    19          return processBytes(b)
    20  }
    21  ```
    22  
    23  ```sh
    24  $ interfacer $(go list ./... | grep -v /vendor/)
    25  foo.go:10:19: f can be io.Reader
    26  ```
    27  
    28  ### Basic idea
    29  
    30  This tool inspects the parameters of your functions to see if they fit
    31  an interface type that is less specific than the current type.
    32  
    33  The example above illustrates this point. Overly specific interfaces
    34  also trigger a warning - if `f` were an `io.ReadCloser`, the same
    35  message would appear.
    36  
    37  It suggests interface types defined both in the func's package and the
    38  package's imports (two levels; direct imports and their direct imports).
    39  
    40  ### False positives
    41  
    42  To avoid false positives, it never does any suggestions on functions
    43  that may be implementing an interface method or a named function type.
    44  
    45  It also skips parameters passed by value (excluding pointers and
    46  interfaces) on unexported functions, since that would introduce extra
    47  allocations where they are usually not worth the tradeoff.
    48  
    49  ### Suppressing warnings
    50  
    51  If a suggestion is technically correct but doesn't make sense, you can
    52  still suppress the warning by mentioning the type in the function name:
    53  
    54  ```go
    55  func ProcessInputFile(f *os.File) error {
    56  	// use as an io.Reader
    57  }
    58  ```