Add formatter NDJSON (#34)

* Add formatter json-stream

* use new json struct in json-stream

* rename json-stream formatter to ndjson

* add ndjson formatter to readme

README.md

@@ -91,6 +91,7 @@ go get -u github.com/mgechev/revive
 - `-formatter [NAME]` - formatter to be used for the output. The currently available formatters are:
   - `default` - will output the failures the same way that `golint` does.
   - `json` - outputs the failures in JSON format.
+  - `ndjson` - outputs the failures as stream in newline delimited JSON (NDJSON) format.
   - `friendly` - outputs the failures when found. Shows summary of all the failures.
   - `stylish` - formats the failures in a table. Keep in mind that it doesn't stream the output so it might be perceived as slower compared to others.
 

config.go

@@ -61,6 +61,7 @@ var allFormatters = []lint.Formatter{
 	&formatter.Stylish{},
 	&formatter.Friendly{},
 	&formatter.JSON{},
+	&formatter.NDJSON{},
 	&formatter.Default{},
 }
 

formatter/ndjson.go

@@ -0,0 +1,34 @@
+package formatter
+
+import (
+	"encoding/json"
+	"os"
+
+	"github.com/mgechev/revive/lint"
+)
+
+// NDJSON is an implementation of the Formatter interface
+// which formats the errors to NDJSON stream.
+type NDJSON struct {
+	Metadata lint.FormatterMetadata
+}
+
+// Name returns the name of the formatter
+func (f *NDJSON) Name() string {
+	return "ndjson"
+}
+
+// Format formats the failures gotten from the lint.
+func (f *NDJSON) Format(failures <-chan lint.Failure, config lint.RulesConfig) (string, error) {
+	enc := json.NewEncoder(os.Stdout)
+	for failure := range failures {
+		obj := jsonObject{}
+		obj.Severity = severity(config, failure)
+		obj.Failure = failure
+		err := enc.Encode(obj)
+		if err != nil {
+			return "", err
+		}
+	}
+	return "", nil
+}