dev: add test for govet custom formatter

Author: jirfag

test/run_test.go

@@ -63,6 +63,10 @@ func TestUnsafeOk(t *testing.T) {
 	testshared.NewLintRunner(t).Run("--enable-all", getTestDataDir("unsafe")).ExpectNoIssues()
 }
 
+func TestGovetCustomFormatter(t *testing.T) {
+	testshared.NewLintRunner(t).Run(getTestDataDir("govet_custom_formatter")).ExpectNoIssues()
+}
+
 func TestSkippedDirsNoMatchArg(t *testing.T) {
 	dir := getTestDataDir("skipdirs", "skip_me", "nested")
 	r := testshared.NewLintRunner(t).Run("--print-issued-lines=false", "--no-config", "--skip-dirs", dir, "-Egolint", dir)

test/testdata/govet_custom_formatter/main.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+)
+
+const (
+	escape = "\x1b"
+	reset  = escape + "[0m"
+	green  = escape + "[32m"
+)
+
+// Bar is a progress bar.
+type Bar float64
+
+var _ fmt.Formatter = Bar(1.0)
+
+// Format the progress bar as output
+func (h Bar) Format(state fmt.State, r rune) {
+	switch r {
+	case 'r':
+	default:
+		panic(fmt.Sprintf("%v: unexpected format character", float64(h)))
+	}
+
+	if h > 1.0 {
+		h = 1.0
+	}
+
+	if h < 0.0 {
+		h = 0.0
+	}
+
+	if state.Flag('-') {
+		h = 1.0 - h
+	}
+
+	width, ok := state.Width()
+	if !ok {
+		// default width of 40
+		width = 40
+	}
+
+	var pad int
+
+	extra := len([]byte(green)) + len([]byte(reset))
+
+	p := make([]byte, width+extra)
+	p[0], p[len(p)-1] = '|', '|'
+	pad += 2
+
+	positive := int(Bar(width-pad) * h)
+	negative := width - pad - positive
+
+	n := 1
+	n += copy(p[n:], green)
+	n += copy(p[n:], bytes.Repeat([]byte("+"), positive))
+	n += copy(p[n:], reset)
+
+	if negative > 0 {
+		copy(p[n:len(p)-1], bytes.Repeat([]byte("-"), negative))
+	}
+
+	_, _ = state.Write(p)
+}
+
+func main() {
+	var b Bar = 0.9
+	_, _ = fmt.Fprintf(os.Stdout, "%r", b)
+}