fix(stacktrace): Ignore SDK subpackage frames

Compared to release v0.3.1, now filteredFrames compares the frame.Module
value instead of frame.AbsPath, and ignores SDK "_test" packages instead
of pattern matching test files and examples.

However confusing it might be, frame.Module holds a package name,
unrelated to Go Modules.

This fixes up the regression introduced in
61d7ccc, which caused frames from
integrations/subpackages to be reported to Sentry.

stacktrace.go

@@ -206,17 +206,24 @@ func extractFrames(pcs []uintptr) []Frame {
 	return frames
 }
 
+// filterFrames filters out stack frames that are not meant to be reported to
+// Sentry. Those are frames internal to the SDK or Go.
 func filterFrames(frames []Frame) []Frame {
+	if len(frames) == 0 {
+		return nil
+	}
+
 	filteredFrames := make([]Frame, 0, len(frames))
 
 	for _, frame := range frames {
-		// go runtime frames
+		// Skip Go internal frames.
 		if frame.Module == "runtime" || frame.Module == "testing" {
 			continue
 		}
-		// sentry internal frames
-		if frame.Module == "github.com/getsentry/sentry-go" ||
-			strings.HasPrefix(frame.Module, "github.com/getsentry/sentry-go.") {
+		// Skip Sentry internal frames, except for frames in _test packages (for
+		// testing).
+		if strings.HasPrefix(frame.Module, "github.com/getsentry/sentry-go") &&
+			!strings.HasSuffix(frame.Module, "_test") {
 			continue
 		}
 		filteredFrames = append(filteredFrames, frame)

stacktrace_test.go

@@ -65,3 +65,97 @@ func TestSplitQualifiedFunctionName(t *testing.T) {
 		})
 	}
 }
+
+//nolint: scopelint // false positive https://github.com/kyoh86/scopelint/issues/4
+func TestFilterFrames(t *testing.T) {
+	tests := []struct {
+		in  []Frame
+		out []Frame
+	}{
+		// sanity check
+		{},
+		// filter out go internals and SDK internals; "sentry-go_test" is
+		// considered outside of the SDK and thus included (useful for testing)
+		{
+			in: []Frame{
+				{
+					Function: "goexit",
+					Module:   "runtime",
+					AbsPath:  "/goroot/src/runtime/asm_amd64.s",
+					InApp:    false,
+				},
+				{
+					Function: "tRunner",
+					Module:   "testing",
+					AbsPath:  "/goroot/src/testing/testing.go",
+					InApp:    false,
+				},
+				{
+					Function: "TestNewStacktrace.func1",
+					Module:   "github.com/getsentry/sentry-go_test",
+					AbsPath:  "/somewhere/sentry/sentry-go/stacktrace_external_test.go",
+					InApp:    true,
+				},
+				{
+					Function: "StacktraceTestHelper.NewStacktrace",
+					Module:   "github.com/getsentry/sentry-go",
+					AbsPath:  "/somewhere/sentry/sentry-go/stacktrace_test.go",
+					InApp:    true,
+				},
+				{
+					Function: "NewStacktrace",
+					Module:   "github.com/getsentry/sentry-go",
+					AbsPath:  "/somewhere/sentry/sentry-go/stacktrace.go",
+					InApp:    true,
+				},
+			},
+			out: []Frame{
+				{
+					Function: "TestNewStacktrace.func1",
+					Module:   "github.com/getsentry/sentry-go_test",
+					AbsPath:  "/somewhere/sentry/sentry-go/stacktrace_external_test.go",
+					InApp:    true,
+				},
+			},
+		},
+		// filter out integrations; SDK subpackages
+		{
+			in: []Frame{
+				{
+					Function: "Example.Integration",
+					Module:   "github.com/getsentry/sentry-go/http/integration",
+					AbsPath:  "/somewhere/sentry/sentry-go/http/integration/integration.go",
+					InApp:    true,
+				},
+				{
+					Function: "(*Handler).Handle",
+					Module:   "github.com/getsentry/sentry-go/http",
+					AbsPath:  "/somewhere/sentry/sentry-go/http/sentryhttp.go",
+					InApp:    true,
+				},
+				{
+					Function: "main",
+					Module:   "main",
+					AbsPath:  "/somewhere/example.com/pkg/main.go",
+					InApp:    true,
+				},
+			},
+			out: []Frame{
+				{
+					Function: "main",
+					Module:   "main",
+					AbsPath:  "/somewhere/example.com/pkg/main.go",
+					InApp:    true,
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run("", func(t *testing.T) {
+			got := filterFrames(tt.in)
+			if diff := cmp.Diff(tt.out, got); diff != "" {
+				t.Errorf("filterFrames() mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}