errorstack_test.go

package errorstack

import (
	"errors"
	"fmt"
	"io"
	"regexp"
	"strings"
	"testing"
)

func TestWithStack_returns_nil_if_error_is_nil(t *testing.T) {
	got := WithStack(nil)
	if got != nil {
		t.Errorf("WithStack(nil): got %#v, expected nil", got)
	}
}

func TestWithStack_keeps_error_message(t *testing.T) {
	tests := []struct {
		err  error
		want string
	}{
		{io.EOF, "EOF"},
		{WithStack(io.EOF), "EOF"},
	}

	for _, tt := range tests {
		got := WithStack(tt.err).Error()
		if got != tt.want {
			t.Errorf("WithStack(%v): got: %v, want %v", tt.err, got, tt.want)
		}
	}
}

func TestWithStack_formats_correctly(t *testing.T) {
	tests := []struct {
		error
		format string
		want   []string
	}{
		{
			WithStack(io.EOF),
			"%s",
			[]string{"EOF"},
		},
		{
			WithStack(io.EOF),
			"%v",
			[]string{"EOF"},
		},
		{
			WithStack(errors.New("error")),
			"%s",
			[]string{"error"},
		},
		{
			WithStack(errors.New("error")),
			"%v",
			[]string{"error"},
		},
	}

	for i, tt := range tests {
		testFormatCompleteCompare(t, i, tt.error, tt.format, tt.want, true)
	}
}

func testFormatRegexp(t *testing.T, n int, arg interface{}, format, want string) {
	t.Helper()
	got := fmt.Sprintf(format, arg)
	gotLines := strings.SplitN(got, "\n", -1)
	wantLines := strings.SplitN(want, "\n", -1)

	if len(wantLines) > len(gotLines) {
		t.Errorf("test %d: wantLines(%d) > gotLines(%d):\n got: %q\nwant: %q", n+1, len(wantLines), len(gotLines), got, want)
		return
	}

	for i, w := range wantLines {
		match, err := regexp.MatchString(w, gotLines[i])
		if err != nil {
			t.Fatal(err)
		}
		if !match {
			t.Errorf("test %d: line %d: fmt.Sprintf(%q, err):\n got: %q\nwant: %q", n+1, i+1, format, got, want)
		}
	}
}

var stackLineR = regexp.MustCompile(`\.`)

// parseBlocks parses input into a slice, where:
//   - incase entry contains a newline, its a stacktrace
//   - incase entry contains no newline, its a solo line.
//
// Detecting stack boundaries only works incase the WithStack-calls are
// to be found on the same line, thats why it is optionally here.
//
// Example use:
//
//	for _, e := range blocks {
//	  if strings.ContainsAny(e, "\n") {
//	    // Match as stack
//	  } else {
//	    // Match as line
//	  }
//	}
func parseBlocks(input string, detectStackboundaries bool) ([]string, error) {
	var blocks []string

	stack := ""
	wasStack := false
	lines := map[string]bool{} // already found lines

	for _, l := range strings.Split(input, "\n") {
		isStackLine := stackLineR.MatchString(l)

		switch {
		case !isStackLine && wasStack:
			blocks = append(blocks, stack, l)
			stack = ""
			lines = map[string]bool{}
		case isStackLine:
			if wasStack {
				// Detecting two stacks after another, possible cause lines match in
				// our tests due to WithStack(WithStack(io.EOF)) on same line.
				if detectStackboundaries {
					if lines[l] {
						if len(stack) == 0 {
							return nil, errors.New("len of block must not be zero here")
						}

						blocks = append(blocks, stack)
						stack = l
						lines = map[string]bool{l: true}
						continue
					}
				}

				stack = stack + "\n" + l
			} else {
				stack = l
			}
			lines[l] = true
		case !isStackLine && !wasStack:
			blocks = append(blocks, l)
		default:
			return nil, errors.New("must not happen")
		}

		wasStack = isStackLine
	}

	// Use up stack
	if stack != "" {
		blocks = append(blocks, stack)
	}
	return blocks, nil
}

func testFormatCompleteCompare(t *testing.T, n int, arg interface{}, format string, want []string, detectStackBoundaries bool) {
	gotStr := fmt.Sprintf(format, arg)

	got, err := parseBlocks(gotStr, detectStackBoundaries)
	if err != nil {
		t.Fatal(err)
	}

	if len(got) != len(want) {
		t.Fatalf("test %d: fmt.Sprintf(%s, err) -> wrong number of blocks: got(%d) want(%d)\n got: %s\nwant: %s\ngotStr: %q",
			n+1, format, len(got), len(want), prettyBlocks(got), prettyBlocks(want), gotStr)
	}

	for i := range got {
		if strings.ContainsAny(want[i], "\n") {
			// Match as stack
			match, err := regexp.MatchString(want[i], got[i])
			if err != nil {
				t.Fatal(err)
			}
			if !match {
				t.Fatalf("test %d: block %d: fmt.Sprintf(%q, err):\ngot:\n%q\nwant:\n%q\nall-got:\n%s\nall-want:\n%s\n",
					n+1, i+1, format, got[i], want[i], prettyBlocks(got), prettyBlocks(want))
			}
		} else {
			// Match as message
			if got[i] != want[i] {
				t.Fatalf("test %d: fmt.Sprintf(%s, err) at block %d got != want:\n got: %q\nwant: %q", n+1, format, i+1, got[i], want[i])
			}
		}
	}
}

func prettyBlocks(blocks []string) string {
	var out []string

	for _, b := range blocks {
		out = append(out, fmt.Sprintf("%v", b))
	}

	return "   " + strings.Join(out, "\n   ")
}