[minor] added support for annotation verbs ('%v', '%+v', '%s', '%+s')

Author: bnkamalesh

errors.go

@@ -2,6 +2,8 @@
 package errors
 
 import (
+	"fmt"
+	"io"
 	"net/http"
 	"runtime"
 	"strings"
@@ -62,24 +64,41 @@ type Error struct {
 func (e *Error) Error() string {
 	if e.original != nil {
 		// string concatenation with + is ~100x faster than fmt.Sprintf()
-		return e.fileLine + " " + e.original.Error()
-		/*
-			// use the following code instead of the above return, to avoid nested filename:line
-			err, _ := e.original.(*Error)
-			if err != nil {
-			    return err.Error()
+		return e.fileLine + ": " + e.message + "\n" + e.original.Error()
+	}
+
+	if e.message != "" {
+		// string concatenation with + is ~100x faster than fmt.Sprintf()
+		return e.fileLine + ": " + e.message
+	}
+
+	// string concatenation with + is ~100x faster than fmt.Sprintf()
+	return e.fileLine + ": " + DefaultMessage
+}
+
+// ErrorWithoutFileLine prints the final string without the stack trace / file+line number
+func (e *Error) ErrorWithoutFileLine() string {
+	if e.original != nil {
+		if e.message != "" {
+			// string concatenation with + is ~100x faster than fmt.Sprintf()
+			msg := e.message + ": "
+			if o, ok := e.original.(*Error); ok {
+				msg += o.ErrorWithoutFileLine()
+			} else {
+				msg += e.original.Error()
 			}
-			return fmt.Sprintf("%s %s", e.fileLine, e.original.Error())
-		*/
+			return msg
+		}
+		return e.original.Error()
 	}
 
 	if e.message != "" {
 		// string concatenation with + is ~100x faster than fmt.Sprintf()
-		return e.fileLine + " " + e.message
+		return e.message
 	}
 
 	// string concatenation with + is ~100x faster than fmt.Sprintf()
-	return e.fileLine + " " + DefaultMessage
+	return e.fileLine
 }
 
 // Message returns the user friendly message stored in the error struct. It will ignore all errors
@@ -101,7 +120,7 @@ func (e *Error) Message() string {
 	}
 
 	if len(messages) > 0 {
-		return strings.Join(messages, ". ")
+		return strings.Join(messages, ": ")
 	}
 
 	return e.Error()
@@ -173,6 +192,37 @@ func (e *Error) Type() errType {
 	return e.eType
 }
 
+// Format implements the verbs supported by Error to be used in fmt annotated/formatted strings
+/*
+%v  - the same output as Message(). i.e. recursively get all the custom messages set by user
+    - if any of the wrapped error is not of type *Error, that will *not* be displayed
+%+v - recursively prints all the messages along with the file & line number. Also includes output of `Error()` of
+non *Error types.
+
+%s  - identical to %v
+%+s - recursively prints all the messages without file & line number. Also includes output `Error()` of
+non *Error types.
+*/
+
+func (e *Error) Format(s fmt.State, verb rune) {
+	switch verb {
+	case 'v':
+		if s.Flag('+') {
+			io.WriteString(s, e.Error())
+		} else {
+			io.WriteString(s, e.Message())
+		}
+	case 's':
+		{
+			if s.Flag('+') {
+				io.WriteString(s, e.ErrorWithoutFileLine())
+			} else {
+				io.WriteString(s, e.Message())
+			}
+		}
+	}
+}
+
 // New returns a new instance of Error with the relavant fields initialized
 func New(msg string) *Error {
 	_, file, line, _ := runtime.Caller(1)

errors_test.go

@@ -52,7 +52,7 @@ func TestError_Error(t *testing.T) {
 				eType:    TypeInternal,
 				fileLine: "",
 			},
-			want: " hello world",
+			want: ": hello world",
 		},
 		{
 			name: "single error, no original error, has fileline",
@@ -62,7 +62,7 @@ func TestError_Error(t *testing.T) {
 				eType:    TypeInternal,
 				fileLine: "/home/user/main.go:60",
 			},
-			want: "/home/user/main.go:60 hello world",
+			want: "/home/user/main.go:60: hello world",
 		},
 		{
 			name: "with original error",
@@ -72,7 +72,7 @@ func TestError_Error(t *testing.T) {
 				eType:    TypeInternal,
 				fileLine: "/home/user/main.go:60",
 			},
-			want: "/home/user/main.go:60 bad error",
+			want: "/home/user/main.go:60: hello world\nbad error",
 		},
 		{
 			name: "with original error of type *Error",
@@ -82,7 +82,7 @@ func TestError_Error(t *testing.T) {
 				eType:    TypeInternal,
 				fileLine: "",
 			},
-			want: fmt.Sprintf(" %s:%d %s", file, line, sampleErrContent),
+			want: fmt.Sprintf(": hello world\n%s:%d: %s", file, line, sampleErrContent),
 		},
 	}
 	for _, tt := range tests {
@@ -94,7 +94,7 @@ func TestError_Error(t *testing.T) {
 				fileLine: tt.fields.fileLine,
 			}
 			if got := e.Error(); got != tt.want {
-				t.Errorf("Error.Error() = %v, want %v", got, tt.want)
+				t.Errorf("Error.Error() = '%v', want '%v'", got, tt.want)
 			}
 		})
 	}
@@ -256,7 +256,7 @@ func TestError_Message(t *testing.T) {
 				eType:    TypeInternal,
 				fileLine: "errors.go:87",
 			},
-			want: "errors.go:87 unknown error occurred",
+			want: "errors.go:87: unknown error occurred",
 		},
 		{
 			name: "Nested error with message",