huge refactoring

internal/pkg/xerror/doc.go

@@ -0,0 +1,7 @@
+/*
+Package xerror helps standardizing
+the errors through the application.
+
+Credits: https://middlemost.com/failure-is-your-domain/
+*/
+package xerror

internal/pkg/xerror/xerror.go

@@ -0,0 +1,152 @@
+package xerror
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+)
+
+// ErrorCode is machine-readable error code.
+type ErrorCode string
+
+const (
+	// InternalCode is an internal error.
+	InternalCode ErrorCode = "internal"
+	// InvalidCode occurs when a validation
+	// failed.
+	InvalidCode ErrorCode = "invalid"
+	// TimeoutCode occurs when something
+	// timed out.
+	TimeoutCode ErrorCode = "timeout"
+)
+
+// Error defines our standard application
+// error.
+type Error struct {
+	code    ErrorCode
+	message string
+	op      string
+	err     error
+}
+
+// Error returns the string representation of the error message.
+func (e Error) Error() string {
+	var buf bytes.Buffer
+	// if wrapping an error, print its Error() message.
+	// Otherwise print the error code & message.
+	if e.err != nil {
+		buf.WriteString(e.err.Error())
+	} else {
+		if e.code != "" {
+			fmt.Fprintf(&buf, "<%s> ", e.code)
+		}
+		buf.WriteString(e.message)
+	}
+	return buf.String()
+}
+
+/*
+New returns a xerror.Error.
+
+Should be used for wrapping an error
+at the end of a function.
+*/
+func New(op string, previous error) error {
+	return &Error{
+		op:  op,
+		err: previous,
+	}
+}
+
+/*
+Invalid returns a xerror.Error.
+
+Should be used when an input
+is wrong.
+*/
+func Invalid(op, message string, previous error) error {
+	return &Error{
+		code:    InvalidCode,
+		message: message,
+		op:      op,
+		err:     previous,
+	}
+}
+
+/*
+Timeout returns a xerror.Error.
+
+Should be used when a timeout occurs.
+*/
+func Timeout(op, message string, previous error) error {
+	return &Error{
+		code:    TimeoutCode,
+		message: message,
+		op:      op,
+		err:     previous,
+	}
+}
+
+// Code returns the code of the root error, if available.
+// Otherwise returns InternalCode.
+func Code(err error) ErrorCode {
+	if err == nil {
+		return ""
+	}
+	e, ok := err.(*Error)
+	if ok && e.code != "" {
+		return e.code
+	}
+	if ok && e.err != nil {
+		return Code(e.err)
+	}
+	return InternalCode
+}
+
+const defaultMessage string = "an internal error has occurred: please contact technical support"
+
+// Message returns the human-readable message of the error, if available.
+// Otherwise returns a generic error message.
+func Message(err error) string {
+	if err == nil {
+		return ""
+	}
+	e, ok := err.(*Error)
+	if ok && e.message != "" {
+		return e.message
+	}
+	if ok && e.err != nil {
+		return Message(e.err)
+	}
+	return defaultMessage
+}
+
+// Op returns the logical operation of the error, if available.
+// Otherwise returns an empty string.
+func Op(err error) string {
+	if err == nil {
+		return ""
+	}
+	e, ok := err.(*Error)
+	if !ok {
+		return ""
+	}
+	var buf bytes.Buffer
+	nestedOp := Op(e.err)
+	if nestedOp != "" {
+		// we want to avoid having the same op chained.
+		if e.op != "" && !strings.Contains(nestedOp, e.op) {
+			fmt.Fprintf(&buf, "%s: %s", e.op, nestedOp)
+		} else {
+			fmt.Fprintf(&buf, "%s", nestedOp)
+		}
+	} else if e.op != "" {
+		fmt.Fprintf(&buf, "%s", e.op)
+	}
+	return buf.String()
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = error(new(Error))
+)

internal/pkg/xerror/xerror_test.go

@@ -0,0 +1,97 @@
+package xerror
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+/*
+Error 1.0: op = "foo"
+Error 1.1: op = "bar"
+Error 1.2: code = "invalid", op = "baz", message = "nested error"
+Error 1.3: message = "root error"
+*/
+func scenario1() error {
+	rootErr := errors.New("root error")
+	nestedErr := Invalid("baz", "nested error", rootErr)
+	wrappingErr := New("bar", nestedErr)
+	return New("foo", wrappingErr)
+}
+
+/*
+Error 2.0: op = "foo"
+Error 2.1: op = "bar"
+Error 2.2: code = "timeout", op = "bar", message = "nested error"
+*/
+func scenario2() error {
+	nestedErr := Timeout("bar", "nested error", nil)
+	wrappingErr := New("bar", nestedErr)
+	return New("foo", wrappingErr)
+}
+
+// Error 3.0: code = "", op = "foo"
+func scenario3() error {
+	return New("foo", nil)
+}
+
+func TestError(t *testing.T) {
+	// should return the Error 1.3
+	// message.
+	err := scenario1()
+	assert.Equal(t, "root error", err.Error())
+	// should return the Error 2.2 message with
+	// its code.
+	err = scenario2()
+	assert.Equal(t, "<timeout> nested error", err.Error())
+}
+
+func TestCode(t *testing.T) {
+	// should be an empty code if no error.
+	assert.Equal(t, "", fmt.Sprintf("%s", Code(nil)))
+	// should be the code of Error 1.2.
+	err := scenario1()
+	assert.Equal(t, InvalidCode, Code(err))
+	// should be the code of Error 2.2.
+	err = scenario2()
+	assert.Equal(t, TimeoutCode, Code(err))
+	// should be the default code.
+	err = scenario3()
+	assert.Equal(t, InternalCode, Code(err))
+	err = errors.New("some error")
+	assert.Equal(t, InternalCode, Code(err))
+}
+
+func TestMessage(t *testing.T) {
+	// should be an empty message if no error.
+	assert.Equal(t, "", Message(nil))
+	// should be the message of Error 1.2.
+	err := scenario1()
+	assert.Equal(t, "nested error", Message(err))
+	// should be the default message.
+	err = errors.New("some error")
+	assert.Equal(t, defaultMessage, Message(err))
+}
+
+func TestOp(t *testing.T) {
+	// should be an empty op if no error.
+	assert.Equal(t, "", Op(nil))
+	// should be the chain of op in this order:
+	// Error 1.0 -> Error 1.1 -> Error 1.2.
+	err := scenario1()
+	assert.Equal(t, "foo: bar: baz", Op(err))
+	/*
+		should be the chain of op in this order:
+		Error 2.0 -> Error 2.1.
+
+		As Error 2.1 and Error 2.2 shares the same
+		op, Error 2.2 op is not displayed.
+	*/
+	err = scenario2()
+	assert.Equal(t, "foo: bar", Op(err))
+	// should be an empty op if not Error.
+	err = errors.New("some error")
+	assert.Equal(t, "", Op(err))
+}