feat: improve error logs when running sync/diff/validate

Currently decK doesn't return very useful and descriptive
errors when configuration files are validated. This is
particularly painful when the configuration is distributed
in several files and the error doesn't specificy which
file contains the error.

Let's take for example the following files:

```
$ cat services.yaml
services:
- name: svc1
  host: mockbin.org
  foo: bar

consumers:
- username: good
- name: bad
```

If we run decK, it will return some obscure and incomplete errors:

```
$ deck sync -s services.yaml -s consumers.yaml
Error: reading file: validating file content: 1 errors occurred:
        services.0: Additional property foo is not allowed
```

This commit is going to improve the way decK handles
configuration validation error logging in order to provide
a more useful description of the problems.
When running decK with the new functionality, the following will
be returned:

```
$ ./deck sync -s services.yaml -s consumers.yaml
Error: 2 errors occurred:
	reading file services.yaml: validating file content: 1 errors occurred:
	validation error: object="bar", err=services.0: Additional property foo is not allowed

	reading file consumers.yaml: validating file content: 3 errors occurred:
	validation error: object={"name":"bad"}, err=consumers.1: Must validate at least one schema (anyOf)
	validation error: object={"name":"bad"}, err=consumers.1: username is required
	validation error: object="bad", err=consumers.1: Additional property name is not allowed
```

Makefile

@@ -6,7 +6,7 @@ test-all: lint test
 
 .PHONY: test
 test:
-	go test -race ./...
+	go test -race -count=1 ./...
 
 .PHONY: lint
 lint:

file/readfile.go

@@ -20,44 +20,48 @@ import (
 // file, depending on the type of each item in filenames, merges the content of
 // these files and renders a Content.
 func getContent(filenames []string) (*Content, error) {
-	var allReaders []io.Reader
 	var workspaces []string
+	var res Content
+	var errs []error
 	for _, fileOrDir := range filenames {
 		readers, err := getReaders(fileOrDir)
 		if err != nil {
 			return nil, err
 		}
-		allReaders = append(allReaders, readers...)
-	}
-	var res Content
-	for _, r := range allReaders {
-		content, err := readContent(r)
-		if err != nil {
-			return nil, fmt.Errorf("reading file: %w", err)
-		}
-		if content.Workspace != "" {
-			workspaces = append(workspaces, content.Workspace)
-		}
-		err = mergo.Merge(&res, content, mergo.WithAppendSlice)
-		if err != nil {
-			return nil, fmt.Errorf("merging file contents: %w", err)
+
+		for filename, r := range readers {
+			content, err := readContent(r)
+			if err != nil {
+				errs = append(errs, fmt.Errorf("reading file %s: %w", filename, err))
+				continue
+			}
+			if content.Workspace != "" {
+				workspaces = append(workspaces, content.Workspace)
+			}
+			err = mergo.Merge(&res, content, mergo.WithAppendSlice)
+			if err != nil {
+				return nil, fmt.Errorf("merging file contents: %w", err)
+			}
 		}
 	}
+	if len(errs) > 0 {
+		return nil, utils.ErrArray{Errors: errs}
+	}
 	if err := validateWorkspaces(workspaces); err != nil {
 		return nil, err
 	}
 	return &res, nil
 }
 
-// getReaders returns back io.Readers representing all the YAML and JSON
-// files in a directory. If fileOrDir is a single file, then it
+// getReaders returns back a map of filename:io.Reader representing all the
+// YAML and JSON files in a directory. If fileOrDir is a single file, then it
 // returns back the reader for the file.
 // If fileOrDir is equal to "-" string, then it returns back a io.Reader
 // for the os.Stdin file descriptor.
-func getReaders(fileOrDir string) ([]io.Reader, error) {
+func getReaders(fileOrDir string) (map[string]io.Reader, error) {
 	// special case where `-` means stdin
 	if fileOrDir == "-" {
-		return []io.Reader{os.Stdin}, nil
+		return map[string]io.Reader{"STDIN": os.Stdin}, nil
 	}
 
 	finfo, err := os.Stat(fileOrDir)
@@ -75,13 +79,13 @@ func getReaders(fileOrDir string) ([]io.Reader, error) {
 		files = append(files, fileOrDir)
 	}
 
-	var res []io.Reader
+	res := make(map[string]io.Reader, len(files))
 	for _, file := range files {
 		f, err := os.Open(file)
 		if err != nil {
 			return nil, fmt.Errorf("opening file: %w", err)
 		}
-		res = append(res, bufio.NewReader(f))
+		res[file] = bufio.NewReader(f)
 	}
 	return res, nil
 }

file/readfile_test.go

@@ -6,9 +6,10 @@ import (
 	"reflect"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
 	"github.com/kong/deck/utils"
 	"github.com/kong/go-kong/kong"
-	"github.com/stretchr/testify/require"
 )
 
 func Test_configFilesInDir(t *testing.T) {
@@ -66,15 +67,17 @@ func Test_getReaders(t *testing.T) {
 	tests := []struct {
 		name string
 		args args
-		want []io.Reader
+		want map[string]io.Reader
 		// length of returned array
 		wantLen int
 		wantErr bool
 	}{
 		{
-			name:    "read from standard input",
-			args:    args{"-"},
-			want:    []io.Reader{os.Stdin},
+			name: "read from standard input",
+			args: args{"-"},
+			want: map[string]io.Reader{
+				"STDIN": os.Stdin,
+			},
 			wantLen: 1,
 			wantErr: false,
 		},
@@ -126,6 +129,29 @@ func Test_getReaders(t *testing.T) {
 	}
 }
 
+func sortSlices(x, y interface{}) bool {
+	var xName, yName string
+	switch xEntity := x.(type) {
+	case FService:
+		yEntity := y.(FService)
+		xName = *xEntity.Name
+		yName = *yEntity.Name
+	case FRoute:
+		yEntity := y.(FRoute)
+		xName = *xEntity.Name
+		yName = *yEntity.Name
+	case FConsumer:
+		yEntity := y.(FConsumer)
+		xName = *xEntity.Username
+		yName = *yEntity.Username
+	case FPlugin:
+		yEntity := y.(FPlugin)
+		xName = *xEntity.Name
+		yName = *yEntity.Name
+	}
+	return xName < yName
+}
+
 func Test_getContent(t *testing.T) {
 	type args struct {
 		filenames []string
@@ -556,7 +582,15 @@ kong.log.set_serialize_value("span_id", parse_traceid(ngx.ctx.KONG_SPANS[1].span
 				t.Errorf("getContent() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
-			require.Equal(t, tt.want, got)
+
+			opt := []cmp.Option{
+				cmpopts.SortSlices(sortSlices),
+				cmpopts.SortSlices(func(a, b *string) bool { return *a < *b }),
+				cmpopts.EquateEmpty(),
+			}
+			if diff := cmp.Diff(got, tt.want, opt...); diff != "" {
+				t.Errorf(diff)
+			}
 		})
 	}
 }

file/validate.go

@@ -1,13 +1,24 @@
 package file
 
 import (
+	"encoding/json"
+	"errors"
 	"fmt"
 
 	"github.com/kong/deck/utils"
 	"github.com/xeipuuv/gojsonschema"
 	"sigs.k8s.io/yaml"
 )
 
+type ValidationError struct {
+	Object string `json:"object"`
+	Err    error  `json:"error"`
+}
+
+func (e *ValidationError) Error() string {
+	return fmt.Sprintf("validation error: object=%s, err=%v", e.Object, e.Err)
+}
+
 func validate(content []byte) error {
 	var c map[string]interface{}
 	err := yaml.Unmarshal(content, &c)
@@ -24,10 +35,14 @@ func validate(content []byte) error {
 	if result.Valid() {
 		return nil
 	}
+
 	var errs utils.ErrArray
 	for _, desc := range result.Errors() {
-		err := fmt.Errorf(desc.String())
-		errs.Errors = append(errs.Errors, err)
+		jsonString, err := json.Marshal(desc.Value())
+		if err != nil {
+			return err
+		}
+		errs.Errors = append(errs.Errors, &ValidationError{Object: string(jsonString), Err: errors.New(desc.String())})
 	}
 	return errs
 }