Utilize tabs for nested error string representation (#36)

- Fixed a bug as a result of which it was impossible to match embedded
errors' key-value pairs with their messages
- Modified error formatting so that every embedded message is indented
and placed on a new line

Example:
```
Error #1
	Error #2 [key2.1=value2.1, key2.2=value2.2]
		Error #3 [key3=value3]
			Resource not found
```

Author: jeyhun

build/install_tools.sh

@@ -15,9 +15,9 @@ $(go env GOPATH)/bin/golangci-lint version | grep ${GOLNT_VERSION} || curl -sSfL
 
 if [[ "${OSTYPE}" == "linux"* ]]; then
   /tmp/typos --version | grep ${TYPOS_VERSION} || wget -qO- https://github.com/crate-ci/typos/releases/download/v${TYPOS_VERSION}/typos-v${TYPOS_VERSION}-x86_64-unknown-linux-musl.tar.gz | tar -zxf - -C /tmp/ ./typos
+  sudo snap install mdl
 elif [[ "${OSTYPE}" == "darwin"* ]]; then
   /tmp/typos --version | grep ${TYPOS_VERSION} || wget -qO- https://github.com/crate-ci/typos/releases/download/v${TYPOS_VERSION}/typos-v${TYPOS_VERSION}-x86_64-apple-darwin.tar.gz | tar -zxf - -C /tmp/ ./typos
 fi
 
 pip3 install addlicense mdv yamllint
-sudo snap install mdl

docs/DOCUMENTATION.md

@@ -25,8 +25,8 @@ require (
 	github.com/jinzhu/now v1.1.5 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	golang.org/x/crypto v0.5.0 // indirect
-	golang.org/x/sys v0.4.0 // indirect
-	golang.org/x/text v0.6.0 // indirect
+	golang.org/x/sys v0.6.0 // indirect
+	golang.org/x/text v0.8.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 

go.mod

@@ -78,8 +78,8 @@ golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.3.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.4.0 h1:Zr2JFtRQNX3BCZ8YtxRE9hNJYC8J6I1MVbMg6owUp18=
-golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0 h1:MVltZSvRTcU2ljQOhs94SXPftV6DCNnZViHeQps87pQ=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.3.0/go.mod h1:q750SLmJuPmVoN1blW3UFBPREJfb1KmY3vwxfr+nFDA=
@@ -89,8 +89,8 @@ golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
 golang.org/x/text v0.3.8/go.mod h1:E6s5w1FMmriuDzIBO73fBruAKo1PCIq6d2Q6DHfQ8WQ=
 golang.org/x/text v0.5.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
-golang.org/x/text v0.6.0 h1:3XmdazWV+ubf7QgHSTWeykHOci5oeekaGJBLkrkaw4k=
-golang.org/x/text v0.6.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
+golang.org/x/text v0.8.0 h1:57P1ETyNKtuIjB4SRd15iJxuhj8Gc416Y78H3qgMh68=
+golang.org/x/text v0.8.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=

go.sum

@@ -99,7 +99,8 @@ func ExampleDataStore_multiInstance() {
 	// [Dev/P1337] Bob: 31 <nil>
 	// [Prod/P1337] John: 36 <nil>
 	// [Dev/P3] Pat: 39 <nil>
-	// Unable to locate record: record not found[ record=[/P3] : 0,]
+	// Unable to locate record [record=[/P3] : 0]
+	//	record not found
 	// 1 <nil>
 	// 1 <nil>
 	// 0 <nil>

pkg/datastore/example_multiinstance_test.go

@@ -97,7 +97,8 @@ func ExampleDataStore_multiTenancy() {
 	// [Coke/P1337] Bob: 31 <nil>
 	// [Pepsi/P1337] John: 36 <nil>
 	// [Coke/P3] Pat: 39 <nil>
-	// Unable to locate record: record not found[ record=[/P3] : 0,]
+	// Unable to locate record [record=[/P3] : 0]
+	//	record not found
 	// 1 <nil>
 	// 1 <nil>
 	// 0 <nil>

pkg/datastore/example_multitenancy_test.go

@@ -22,6 +22,7 @@ import (
 	"context"
 	"fmt"
 	"reflect"
+	"strings"
 	"unsafe"
 )
 
@@ -43,33 +44,38 @@ const (
 	DB_ROLE           = ErrorContextKey("DbRole")
 )
 
-func contextToString(ctx interface{}) string {
-	ctxStr := ""
-	contextValues := reflect.ValueOf(ctx).Elem()
-	contextKeys := reflect.TypeOf(ctx).Elem()
-
-	if contextKeys.Kind() == reflect.Struct {
-		for i := 0; i < contextValues.NumField(); i++ {
-			reflectValue := contextValues.Field(i)
-			reflectValue = reflect.NewAt(reflectValue.Type(), unsafe.Pointer(reflectValue.UnsafeAddr())).Elem()
-
-			reflectField := contextKeys.Field(i)
-
-			if reflectField.Name == "Context" {
-				ctxStr += contextToString(reflectValue.Interface())
-			} else {
-				switch reflectField.Name {
-				case "key":
-					ctxStr += fmt.Sprintf(" %+v=", reflectValue.Interface())
-				case "val":
-					ctxStr += fmt.Sprintf("%+v,", reflectValue.Interface())
-				default:
-					ctxStr += fmt.Sprintf("%+v=%+v,", reflectField.Name, reflectValue.Interface())
-				}
+func contextToString(ctx context.Context) string {
+	contextType := reflect.TypeOf(ctx).Elem()
+	if contextType.Kind() != reflect.Struct {
+		return ""
+	}
+
+	contextValue := reflect.ValueOf(ctx).Elem()
+	numFields := contextValue.NumField()
+	ctxStrings := make([]string, 0, numFields)
+	for i := 0; i < numFields; i++ {
+		reflectValue := contextValue.Field(i)
+		reflectValue = reflect.NewAt(reflectValue.Type(), unsafe.Pointer(reflectValue.UnsafeAddr())).Elem()
+
+		reflectField := contextType.Field(i)
+		switch reflectField.Name {
+		case "Context":
+			innerCtxStr := contextToString(reflectValue.Interface().(context.Context))
+			if len(innerCtxStr) > 0 {
+				ctxStrings = append(ctxStrings, innerCtxStr+", ")
 			}
+		case "key":
+			keyStr := fmt.Sprintf("%+v=", reflectValue.Interface())
+			ctxStrings = append(ctxStrings, keyStr)
+		case "val":
+			valueStr := fmt.Sprintf("%+v", reflectValue.Interface())
+			ctxStrings = append(ctxStrings, valueStr)
+		default:
+			str := fmt.Sprintf("%+v=%+v,", reflectField.Name, reflectValue.Interface())
+			ctxStrings = append(ctxStrings, str)
 		}
 	}
-	return ctxStr
+	return strings.Join(ctxStrings, "")
 }
 
 type DbError struct {
@@ -79,14 +85,38 @@ type DbError struct {
 }
 
 func (e *DbError) Error() string {
-	str := e.msg
+	var errStrBuilder strings.Builder
+
+	// Add error's own message
+	errStrBuilder.WriteString(e.msg)
+
+	// Add error's key-value pairs
+	if e.ctx != nil {
+		errStrBuilder.WriteString(" [")
+		errStrBuilder.WriteString(contextToString(e.ctx))
+		errStrBuilder.WriteRune(']')
+	}
+
+	// Add nested error on a new line
 	if e.err != nil {
-		str = str + ": " + e.err.Error()
+		errStrBuilder.WriteRune('\n')
+		errStrBuilder.WriteString(e.err.Error())
 	}
-	if e.ctx != nil {
-		str = str + "[" + contextToString(e.ctx) + "]"
+
+	// Indent each nested error
+	errStr := errStrBuilder.String()
+	if split := strings.Split(errStr, "\n"); len(split) > 1 {
+		errStrBuilder.Reset()
+		for i := range split {
+			split[i] = strings.TrimSpace(split[i])
+			for tabsPrinted := 0; tabsPrinted < i; tabsPrinted++ {
+				split[i] = "\t" + split[i]
+			}
+		}
+		errStr = strings.Join(split, "\n")
 	}
-	return str
+
+	return errStr
 }
 
 func (e *DbError) Is(target error) bool {

pkg/errors/error_codes.go

@@ -0,0 +1,62 @@
+package errors_test
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	. "github.com/vmware-labs/multi-tenant-persistence-for-saas/pkg/errors"
+)
+
+func TestErrorToStringConversion_ContextValuesPlacing(t *testing.T) {
+	assert := assert.New(t)
+	t.Parallel()
+
+	err4 := errors.New("Resource not found")
+	err3 := ErrBaseDb.With("Error #3").WithValue("key3", "value3").Wrap(err4)
+	err2 := ErrBaseDb.With("Error #2").WithValue("key2.1", "value2.1").
+		WithValue("key2.2", "value2.2").Wrap(err3)
+	err1 := ErrBaseDb.With("Error #1").Wrap(err2)
+
+	var actualErrStr string = err1.Error()
+	matched, err := regexp.MatchString("\\] *\\[", actualErrStr)
+	assert.NoError(err)
+	assert.False(matched, "Expected error's string version not to place all context values at the very end")
+
+	const expectedErrStr = `Error #1
+	Error #2 [key2.1=value2.1, key2.2=value2.2]
+		Error #3 [key3=value3]
+			Resource not found`
+	assert.Equal(expectedErrStr, actualErrStr)
+}
+
+func TestErrorToStringConversion_MultilineWithIndentation(t *testing.T) {
+	assert := assert.New(t)
+	t.Parallel()
+
+	var err error = ErrBaseDb.With("Error #6")
+	const numEmbeddedErrors = 5
+	for i := numEmbeddedErrors; i > 0; i-- {
+		err = ErrBaseDb.With(fmt.Sprintf("Error #%d", i)).Wrap(err)
+	}
+
+	actualErrStr := err.Error()
+	assert.Equalf(numEmbeddedErrors, strings.Count(actualErrStr, "\n"), "Expected error to contain %d newlines", numEmbeddedErrors)
+
+	expectedNumTabs := 5
+	for i := 0; i < numEmbeddedErrors; i++ {
+		expectedNumTabs += i
+	}
+	assert.Equalf(expectedNumTabs, strings.Count(actualErrStr, "\t"), "Expected error to contain %d tabs", expectedNumTabs)
+
+	const expectedErrStr = `Error #1
+	Error #2
+		Error #3
+			Error #4
+				Error #5
+					Error #6`
+	assert.Equal(expectedErrStr, actualErrStr)
+}