Ccmtaylor compose (#29)

Ccmtaylor compose

compose.go

@@ -0,0 +1,76 @@
+package sqlhooks
+
+import (
+	"context"
+	"fmt"
+)
+
+// Compose allows for composing multiple Hooks into one.
+// It runs every callback on every hook in argument order,
+// even if previous hooks return an error.
+// If multiple hooks return errors, the error return value will be
+// MultipleErrors, which allows for introspecting the errors if necessary.
+func Compose(hooks ...Hooks) Hooks {
+	return composed(hooks)
+}
+
+type composed []Hooks
+
+func (c composed) Before(ctx context.Context, query string, args ...interface{}) (context.Context, error) {
+	var errors []error
+	for _, hook := range c {
+		c, err := hook.Before(ctx, query, args...)
+		if err != nil {
+			errors = append(errors, err)
+		}
+		if c != nil {
+			ctx = c
+		}
+	}
+	return ctx, wrapErrors(nil, errors)
+}
+
+func (c composed) After(ctx context.Context, query string, args ...interface{}) (context.Context, error) {
+	var errors []error
+	for _, hook := range c {
+		var err error
+		c, err := hook.After(ctx, query, args...)
+		if err != nil {
+			errors = append(errors, err)
+		}
+		if c != nil {
+			ctx = c
+		}
+	}
+	return ctx, wrapErrors(nil, errors)
+}
+
+func (c composed) OnError(ctx context.Context, cause error, query string, args ...interface{}) error {
+	var errors []error
+	for _, hook := range c {
+		if onErrorer, ok := hook.(OnErrorer); ok {
+			if err := onErrorer.OnError(ctx, cause, query, args...); err != nil && err != cause {
+				errors = append(errors, err)
+			}
+		}
+	}
+	return wrapErrors(cause, errors)
+}
+
+func wrapErrors(def error, errors []error) error {
+	switch len(errors) {
+	case 0:
+		return def
+	case 1:
+		return errors[0]
+	default:
+		return MultipleErrors(errors)
+	}
+}
+
+// MultipleErrors is an error that contains multiple errors.
+type MultipleErrors []error
+
+func (m MultipleErrors) Error() string {
+	return fmt.Sprint("multiple errors:", []error(m))
+}

compose_1_13.go

@@ -0,0 +1,26 @@
+// +build go1.13
+
+package sqlhooks
+
+import "errors"
+
+// Is returns true if any of the wrapped errors is target according to errors.Is()
+func (m MultipleErrors) Is(target error) bool {
+	for _, err := range m {
+		if errors.Is(err, target) {
+			return true
+		}
+	}
+	return false
+}
+
+// Is tries to convert each wrapped error to target with errors.As() and returns true that succeeds.
+// If none of the errors are convertible, returns false.
+func (m MultipleErrors) As(target interface{}) bool {
+	for _, err := range m {
+		if errors.As(err, &target) {
+			return true
+		}
+	}
+	return false
+}

compose_test.go

@@ -0,0 +1,96 @@
+package sqlhooks
+
+import (
+	"context"
+	"errors"
+	"reflect"
+	"testing"
+)
+
+var (
+	oops     = errors.New("oops")
+	oopsHook = &testHooks{
+		before: func(ctx context.Context, query string, args ...interface{}) (context.Context, error) {
+			return ctx, oops
+		},
+		after: func(ctx context.Context, query string, args ...interface{}) (context.Context, error) {
+			return ctx, oops
+		},
+		onError: func(ctx context.Context, err error, query string, args ...interface{}) error {
+			return oops
+		},
+	}
+	okHook = &testHooks{
+		before: func(ctx context.Context, query string, args ...interface{}) (context.Context, error) {
+			return ctx, nil
+		},
+		after: func(ctx context.Context, query string, args ...interface{}) (context.Context, error) {
+			return ctx, nil
+		},
+		onError: func(ctx context.Context, err error, query string, args ...interface{}) error {
+			return nil
+		},
+	}
+)
+
+func TestCompose(t *testing.T) {
+	for _, it := range []struct {
+		name  string
+		hooks Hooks
+		want  error
+	}{
+		{"happy case", Compose(okHook, okHook), nil},
+		{"no hooks", Compose(), nil},
+		{"multiple errors", Compose(oopsHook, okHook, oopsHook), MultipleErrors([]error{oops, oops})},
+		{"single error", Compose(okHook, oopsHook, okHook), oops},
+	} {
+		t.Run(it.name, func(t *testing.T) {
+			t.Run("Before", func(t *testing.T) {
+				_, got := it.hooks.Before(context.Background(), "query")
+				if !reflect.DeepEqual(it.want, got) {
+					t.Errorf("unexpected error. want: %q, got: %q", it.want, got)
+				}
+			})
+			t.Run("After", func(t *testing.T) {
+				_, got := it.hooks.After(context.Background(), "query")
+				if !reflect.DeepEqual(it.want, got) {
+					t.Errorf("unexpected error. want: %q, got: %q", it.want, got)
+				}
+			})
+			t.Run("OnError", func(t *testing.T) {
+				cause := errors.New("crikey")
+				want := it.want
+				if want == nil {
+					want = cause
+				}
+				got := it.hooks.(OnErrorer).OnError(context.Background(), cause, "query")
+				if !reflect.DeepEqual(want, got) {
+					t.Errorf("unexpected error. want: %q, got: %q", want, got)
+				}
+			})
+		})
+	}
+}
+
+func TestWrapErrors(t *testing.T) {
+	var (
+		err1 = errors.New("oops")
+		err2 = errors.New("oops2")
+	)
+	for _, it := range []struct {
+		name   string
+		def    error
+		errors []error
+		want   error
+	}{
+		{"no errors", err1, nil, err1},
+		{"single error", nil, []error{err1}, err1},
+		{"multiple errors", nil, []error{err1, err2}, MultipleErrors([]error{err1, err2})},
+	} {
+		t.Run(it.name, func(t *testing.T) {
+			if want, got := it.want, wrapErrors(it.def, it.errors); !reflect.DeepEqual(want, got) {
+				t.Errorf("unexpected wrapping. want: %q, got %q", want, got)
+			}
+		})
+	}
+}

sqlhooks_test.go

@@ -35,7 +35,7 @@ func (h *testHooks) After(ctx context.Context, query string, args ...interface{}
 	return h.after(ctx, query, args...)
 }
 
-func (h *testHooks) ErrHook(ctx context.Context, err error, query string, args ...interface{}) error {
+func (h *testHooks) OnError(ctx context.Context, err error, query string, args ...interface{}) error {
 	return h.onError(ctx, err, query, args...)
 }