feat(errors): add errors package (#5741)

### Summary

Add errors package

#### Related Issues / PR's

https://github.com/SigNoz/signoz/pull/5710

pkg/errors/doc.go

@@ -0,0 +1,3 @@
+// package error contains error related utilities. Use this package when
+// a well-defined error has to be shown.
+package errors

pkg/errors/errors.go

@@ -0,0 +1,118 @@
+package errors
+
+import (
+	"fmt"
+)
+
+// base is the fundamental struct that implements the error interface.
+// The order of the struct is 'TCMEUA'.
+type base struct {
+	// t denotes the custom type of the error.
+	t typ
+	// c denotes the short code for the error message.
+	c string
+	// m contains error message passed through errors.New.
+	m string
+	// e is the actual error being wrapped.
+	e error
+	// u denotes the url for the documentation (if present) for the error.
+	u string
+	// a denotes any additional error messages (if present).
+	a []string
+}
+
+// base implements Error interface.
+func (b *base) Error() string {
+	if b.e != nil {
+		return b.e.Error()
+	}
+
+	return fmt.Sprintf("%s(%s): %s", b.t.s, b.c, b.m)
+}
+
+// New returns a base error. It requires type, code and message as input.
+func New(t typ, code string, message string) *base {
+	return &base{
+		t: t,
+		c: code,
+		m: message,
+		e: nil,
+		u: "",
+		a: []string{},
+	}
+}
+
+// Newf returns a new base by formatting the error message with the supplied format specifier.
+func Newf(t typ, code string, format string, args ...interface{}) *base {
+	return &base{
+		t: t,
+		c: code,
+		m: fmt.Sprintf(format, args...),
+		e: nil,
+	}
+}
+
+// Wrapf returns a new error by formatting the error message with the supplied format specifier
+// and wrapping another error with base.
+func Wrapf(cause error, t typ, code string, format string, args ...interface{}) *base {
+	return &base{
+		t: t,
+		c: code,
+		m: fmt.Sprintf(format, args...),
+		e: cause,
+	}
+}
+
+// WithUrl adds a url to the base error and returns a new base error.
+func (b *base) WithUrl(u string) *base {
+	return &base{
+		t: b.t,
+		c: b.c,
+		m: b.m,
+		e: b.e,
+		u: u,
+		a: b.a,
+	}
+}
+
+// WithUrl adds additional messages to the base error and returns a new base error.
+func (b *base) WithAdditional(a ...string) *base {
+	return &base{
+		t: b.t,
+		c: b.c,
+		m: b.m,
+		e: b.e,
+		u: b.u,
+		a: a,
+	}
+}
+
+// Unwrapb is a combination of built-in errors.As and type casting.
+// It finds the first error in cause that matches base,
+// and if one is found, returns the individual fields of base.
+// Otherwise, it returns TypeInternal, the original error string
+// and the error itself.
+//
+//lint:ignore ST1008 we want to return arguments in the 'TCMEUA' order of the struct
+func Unwrapb(cause error) (typ, string, string, error, string, []string) {
+	base, ok := cause.(*base)
+	if ok {
+		return base.t, base.c, base.m, base.e, base.u, base.a
+	}
+
+	return TypeInternal, "", cause.Error(), cause, "", []string{}
+}
+
+// Ast checks if the provided error matches the specified custom error type.
+func Ast(cause error, typ typ) bool {
+	t, _, _, _, _, _ := Unwrapb(cause)
+
+	return t == typ
+}
+
+// Ast checks if the provided error matches the specified custom error code.
+func Asc(cause error, code string) bool {
+	_, c, _, _, _, _ := Unwrapb(cause)
+
+	return c == code
+}

pkg/errors/errors_test.go

@@ -0,0 +1,53 @@
+package errors
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNew(t *testing.T) {
+	typ := typ{"test-error"}
+	err := New(typ, "code", "test error info")
+	assert.NotNil(t, err)
+}
+
+func TestNewf(t *testing.T) {
+	typ := typ{"test-error"}
+	err := Newf(typ, "test-code", "test error info with %s", "string")
+	assert.NotNil(t, err)
+	assert.Equal(t, "test-error(test-code): test error info with string", err.Error())
+}
+
+func TestWrapf(t *testing.T) {
+	typ := typ{"test-error"}
+	err := Wrapf(errors.New("original error"), typ, "test-code", "info for err %d", 2)
+	assert.NotNil(t, err)
+}
+
+func TestError(t *testing.T) {
+	typ := typ{"test-error"}
+	err1 := New(typ, "test-code", "info for err1")
+	assert.Equal(t, "test-error(test-code): info for err1", err1.Error())
+
+	err2 := Wrapf(err1, typ, "test-code", "info for err2")
+	assert.Equal(t, "test-error(test-code): info for err1", err2.Error())
+}
+
+func TestUnwrapb(t *testing.T) {
+	typ := typ{"test-error"}
+	oerr := errors.New("original error")
+	berr := Wrapf(oerr, typ, "test-code", "this is a base err").WithUrl("https://docs").WithAdditional("additional err")
+
+	atyp, acode, amessage, aerr, au, aa := Unwrapb(berr)
+	assert.Equal(t, typ, atyp)
+	assert.Equal(t, "test-code", acode)
+	assert.Equal(t, "this is a base err", amessage)
+	assert.Equal(t, oerr, aerr)
+	assert.Equal(t, "https://docs", au)
+	assert.Equal(t, []string{"additional err"}, aa)
+
+	atyp, _, _, _, _, _ = Unwrapb(oerr)
+	assert.Equal(t, TypeInternal, atyp)
+}

pkg/errors/type.go

@@ -0,0 +1,14 @@
+package errors
+
+var (
+	TypeInvalidInput     typ = typ{"invalid-input"}
+	TypeInternal             = typ{"internal"}
+	TypeUnsupported          = typ{"unsupported"}
+	TypeNotFound             = typ{"not-found"}
+	TypeMethodNotAllowed     = typ{"method-not-allowed"}
+	TypeAlreadyExists        = typ{"already-exists"}
+	TypeUnauthenticated      = typ{"unauthenticated"}
+)
+
+// Defines custom error types
+type typ struct{ s string }

pkg/errors/type_test.go

@@ -0,0 +1,18 @@
+package errors
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestString(t *testing.T) {
+	typ := typ{"test-error"}
+	assert.Equal(t, typ.s, "test-error")
+}
+
+func TestEquals(t *testing.T) {
+	typ1 := typ{"test-error"}
+	typ2 := typ{"test-error"}
+	assert.True(t, typ1 == typ2)
+}