Merge pull request #204 from pace/hide-error-types

Add error hiding func to only forward explicit and context errors

maintenance/errors/context.go

@@ -0,0 +1,34 @@
+package errors
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+)
+
+// Hide checks whether the given error err is a context.Canceled or
+// context.DeadlineExceeded error and if so exposes these errors as
+// wrapped errors while maintaining the given err as string. If
+// the optional exposedErr is provided, it is attached as prefix
+// to the returned error. If the given err is not any of the above
+// ones, the given exposedErr (if present) is wrapped as prefix
+// to the returned error.
+func Hide(ctx context.Context, err, exposedErr error) error {
+	ret := errors.New(err.Error())
+	if exposedErr != nil {
+		ret = fmt.Errorf("%w: %s", exposedErr, err)
+	}
+
+	if ctx.Err() == context.Canceled && errors.Is(err, context.Canceled) {
+		s := strings.TrimSuffix(ret.Error(), context.Canceled.Error())
+		return fmt.Errorf("%s%w", s, context.Canceled)
+	}
+
+	if ctx.Err() == context.DeadlineExceeded && errors.Is(err, context.DeadlineExceeded) {
+		s := strings.TrimSuffix(ret.Error(), context.DeadlineExceeded.Error())
+		return fmt.Errorf("%s%w", s, context.DeadlineExceeded)
+	}
+
+	return ret
+}

maintenance/errors/context_test.go

@@ -0,0 +1,149 @@
+package errors
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestHide(t *testing.T) {
+	iAmAnError := errors.New("i am an error")
+	iAmAnotherError := errors.New("i am another error")
+
+	backgroundContext := context.Background()
+	canceledContext, cancel := context.WithCancel(backgroundContext)
+	cancel()
+
+	exceededContext, _ := context.WithTimeout(backgroundContext, time.Millisecond)
+	time.Sleep(2 * time.Millisecond)
+
+	type args struct {
+		ctx        context.Context
+		err        error
+		exposedErr error
+	}
+	tests := []struct {
+		name string
+		args args
+		want error
+	}{
+		{
+			name: "normal_context_no_error_nothing_exposed",
+			args: args{
+				ctx:        backgroundContext,
+				err:        iAmAnError,
+				exposedErr: nil,
+			},
+			want: iAmAnError,
+		},
+		{
+			name: "normal_context_no_error_with_exposed",
+			args: args{
+				ctx:        backgroundContext,
+				err:        iAmAnError,
+				exposedErr: iAmAnotherError,
+			},
+			want: fmt.Errorf("%w: %s", iAmAnotherError, iAmAnError),
+		},
+		{
+			name: "normal_context_with_error_nothing_exposed",
+			args: args{
+				ctx:        backgroundContext,
+				err:        fmt.Errorf("%s: %w", iAmAnError, context.Canceled),
+				exposedErr: nil,
+			},
+			want: fmt.Errorf("%s: %s", iAmAnError, context.Canceled),
+		},
+		{
+			name: "normal_context_with_error_with_exposed",
+			args: args{
+				ctx:        backgroundContext,
+				err:        fmt.Errorf("%s: %w", iAmAnError, context.Canceled),
+				exposedErr: iAmAnotherError,
+			},
+			want: fmt.Errorf("%w: %s: %s", iAmAnotherError, iAmAnError, context.Canceled),
+		},
+		{
+			name: "canceled_context_no_error_nothing_exposed",
+			args: args{
+				ctx:        canceledContext,
+				err:        iAmAnError,
+				exposedErr: nil,
+			},
+			want: iAmAnError,
+		},
+		{
+			name: "canceled_context_no_error_with_exposed",
+			args: args{
+				ctx:        canceledContext,
+				err:        iAmAnError,
+				exposedErr: iAmAnotherError,
+			},
+			want: fmt.Errorf("%w: %s", iAmAnotherError, iAmAnError),
+		},
+		{
+			name: "canceled_context_with_error_nothing_exposed",
+			args: args{
+				ctx:        canceledContext,
+				err:        fmt.Errorf("%s: %w", iAmAnError, context.Canceled),
+				exposedErr: nil,
+			},
+			want: fmt.Errorf("%s: %w", iAmAnError, context.Canceled),
+		},
+		{
+			name: "canceled_context_with_error_with_exposed",
+			args: args{
+				ctx:        canceledContext,
+				err:        fmt.Errorf("%s: %w", iAmAnError, context.Canceled),
+				exposedErr: iAmAnotherError,
+			},
+			want: fmt.Errorf("%s: %s: %w", iAmAnotherError, iAmAnError, context.Canceled),
+		},
+		{
+			name: "exceeded_context_no_error_nothing_exposed",
+			args: args{
+				ctx:        exceededContext,
+				err:        iAmAnError,
+				exposedErr: nil,
+			},
+			want: iAmAnError,
+		},
+		{
+			name: "exceeded_context_no_error_with_exposed",
+			args: args{
+				ctx:        exceededContext,
+				err:        iAmAnError,
+				exposedErr: iAmAnotherError,
+			},
+			want: fmt.Errorf("%w: %s", iAmAnotherError, iAmAnError),
+		},
+		{
+			name: "exceeded_context_with_error_nothing_exposed",
+			args: args{
+				ctx:        exceededContext,
+				err:        fmt.Errorf("%s: %w", iAmAnError, context.DeadlineExceeded),
+				exposedErr: nil,
+			},
+			want: fmt.Errorf("%s: %w", iAmAnError, context.DeadlineExceeded),
+		},
+		{
+			name: "exceeded_context_with_error_with_exposed",
+			args: args{
+				ctx:        exceededContext,
+				err:        fmt.Errorf("%s: %w", iAmAnError, context.DeadlineExceeded),
+				exposedErr: iAmAnotherError,
+			},
+			want: fmt.Errorf("%s: %s: %w", iAmAnotherError, iAmAnError, context.DeadlineExceeded),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := Hide(tt.args.ctx, tt.args.err, tt.args.exposedErr)
+			require.Equal(t, tt.want, got)
+		})
+	}
+}