fix(dslx): remove Observations from Maybe (ooni#1385)

I forgot to commit this diff as part of
ooni#1383.

Doing it now.

Reference issue: ooni/probe#2614.

internal/dslx/dns.go

@@ -107,9 +107,8 @@ func DNSLookupGetaddrinfo(rt Runtime) Func[*DomainToResolve, *ResolvedAddresses]
 		}
 
 		return &Maybe[*ResolvedAddresses]{
-			Error:        err,
-			Observations: maybeTraceToObservations(trace),
-			State:        state,
+			Error: err,
+			State: state,
 		}
 	})
 }
@@ -158,9 +157,8 @@ func DNSLookupUDP(rt Runtime, endpoint string) Func[*DomainToResolve, *ResolvedA
 		}
 
 		return &Maybe[*ResolvedAddresses]{
-			Error:        err,
-			Observations: maybeTraceToObservations(trace),
-			State:        state,
+			Error: err,
+			State: state,
 		}
 	})
 }

internal/dslx/fxcore.go

@@ -22,9 +22,8 @@ type Operation[A, B any] func(ctx context.Context, a A) *Maybe[B]
 func (op Operation[A, B]) Apply(ctx context.Context, a *Maybe[A]) *Maybe[B] {
 	if a.Error != nil {
 		return &Maybe[B]{
-			Error:        a.Error,
-			Observations: a.Observations,
-			State:        *new(B), // zero value
+			Error: a.Error,
+			State: *new(B), // zero value
 		}
 	}
 	return op(ctx, a.State)
@@ -36,9 +35,6 @@ type Maybe[State any] struct {
 	// Error is either the error that occurred or nil.
 	Error error
 
-	// Observations contains the collected observations.
-	Observations []*Observations
-
 	// State contains state passed between function calls. You should
 	// only access State when Error is nil and Skipped is false.
 	State State
@@ -47,9 +43,8 @@ type Maybe[State any] struct {
 // NewMaybeWithValue constructs a Maybe containing the given value.
 func NewMaybeWithValue[State any](value State) *Maybe[State] {
 	return &Maybe[State]{
-		Error:        nil,
-		Observations: []*Observations{},
-		State:        value,
+		Error: nil,
+		State: value,
 	}
 }
 
@@ -74,18 +69,16 @@ func (h *compose2Func[A, B, C]) Apply(ctx context.Context, a *Maybe[A]) *Maybe[C
 
 	if mb.Error != nil {
 		return &Maybe[C]{
-			Error:        mb.Error,
-			Observations: mb.Observations,
-			State:        *new(C), // zero value
+			Error: mb.Error,
+			State: *new(C), // zero value
 		}
 	}
 
 	mc := h.g.Apply(ctx, mb)
 	runtimex.Assert(mc != nil, "h.g.Apply returned a nil pointer")
 
 	return &Maybe[C]{
-		Error:        mc.Error,
-		Observations: append(mb.Observations, mc.Observations...), // merge observations
-		State:        mc.State,
+		Error: mc.Error,
+		State: mc.State,
 	}
 }

internal/dslx/fxcore_test.go

@@ -27,11 +27,6 @@ func (f *fn) Apply(ctx context.Context, i *Maybe[int]) *Maybe[int] {
 	return &Maybe[int]{
 		Error: f.err,
 		State: i.State + 1,
-		Observations: []*Observations{
-			{
-				NetworkEvents: []*model.ArchivalNetworkEvent{{Tags: []string{"apply"}}},
-			},
-		},
 	}
 }
 
@@ -50,9 +45,8 @@ func TestStageAdapter(t *testing.T) {
 
 		// create input that contains an error
 		input := &Maybe[*DomainToResolve]{
-			Error:        errors.New("mocked error"),
-			Observations: []*Observations{},
-			State:        nil,
+			Error: errors.New("mocked error"),
+			State: nil,
 		}
 
 		// run the pipeline
@@ -91,9 +85,6 @@ func TestCompose2(t *testing.T) {
 				if r.Error != tt.err {
 					t.Fatalf("unexpected error")
 				}
-				if len(r.Observations) != tt.numObs {
-					t.Fatalf("unexpected number of (merged) observations")
-				}
 			})
 		}
 	})

internal/dslx/httpcore.go

@@ -151,9 +151,8 @@ func HTTPRequest(rt Runtime, options ...HTTPRequestOption) Func[*HTTPConnection,
 		}
 
 		return &Maybe[*HTTPResponse]{
-			Error:        err,
-			Observations: observations,
-			State:        state,
+			Error: err,
+			State: state,
 		}
 	})
 }

internal/dslx/httpquic.go

@@ -35,9 +35,8 @@ func HTTPConnectionQUIC(rt Runtime) Func[*QUICConnection, *HTTPConnection] {
 			Transport:             httpTransport,
 		}
 		return &Maybe[*HTTPConnection]{
-			Error:        nil,
-			Observations: nil,
-			State:        state,
+			Error: nil,
+			State: state,
 		}
 	})
 }

internal/dslx/httptcp.go

@@ -36,9 +36,8 @@ func HTTPConnectionTCP(rt Runtime) Func[*TCPConnection, *HTTPConnection] {
 			Transport:             httpTransport,
 		}
 		return &Maybe[*HTTPConnection]{
-			Error:        nil,
-			Observations: nil,
-			State:        state,
+			Error: nil,
+			State: state,
 		}
 	})
 }

internal/dslx/httptls.go

@@ -36,9 +36,8 @@ func HTTPConnectionTLS(rt Runtime) Func[*TLSConnection, *HTTPConnection] {
 			Transport:             httpTransport,
 		}
 		return &Maybe[*HTTPConnection]{
-			Error:        nil,
-			Observations: nil,
-			State:        state,
+			Error: nil,
+			State: state,
 		}
 	})
 }

internal/dslx/quic.go

@@ -71,9 +71,8 @@ func QUICHandshake(rt Runtime, options ...TLSHandshakeOption) Func[*Endpoint, *Q
 		}
 
 		return &Maybe[*QUICConnection]{
-			Error:        err,
-			Observations: maybeTraceToObservations(trace),
-			State:        state,
+			Error: err,
+			State: state,
 		}
 	})
 }

internal/dslx/tcp.go

@@ -55,9 +55,8 @@ func TCPConnect(rt Runtime) Func[*Endpoint, *TCPConnection] {
 		}
 
 		return &Maybe[*TCPConnection]{
-			Error:        err,
-			Observations: maybeTraceToObservations(trace),
-			State:        state,
+			Error: err,
+			State: state,
 		}
 	})
 }

internal/dslx/tls.go

@@ -96,9 +96,8 @@ func TLSHandshake(rt Runtime, options ...TLSHandshakeOption) Func[*TCPConnection
 		}
 
 		return &Maybe[*TLSConnection]{
-			Error:        err,
-			Observations: maybeTraceToObservations(trace),
-			State:        state,
+			Error: err,
+			State: state,
 		}
 	})
 }

internal/tutorial/dslx/chapter02/README.md

@@ -107,21 +107,6 @@ type Subresult struct {
 
 ```
 
-Subresult.mergeObservations merges the observations collected during
-a measurement with the Subresult output data format.
-
-```Go
-
-func (tk *Subresult) mergeObservations(obs []*dslx.Observations) {
-	for _, o := range obs {
-		tk.NetworkEvents = append(tk.NetworkEvents, o.NetworkEvents...)
-		tk.TCPConnect = append(tk.TCPConnect, o.TCPConnect...)
-		tk.TLSHandshakes = append(tk.TLSHandshakes, o.TLSHandshakes...)
-	}
-}
-
-```
-
 ## The Measurer
 
 The `Measurer` performs the measurement and implements `ExperimentMeasurer`; i.e., the
@@ -429,20 +414,6 @@ Store the control failure if any.
 
 ```
 
-The measurement result not only contains the potential error, but also
-observations that have been collected during each step of the measurement pipeline.
-Observations are for example network events like read and write operations,
-TLS handshakes, or DNS queries. We as experiment programmers are responsible for
-extracting these observations from the dslx measurement result and storing
-them in the `TestKeys`, which is precisely what `Subresult.mergeObservations`
-(implemented above) does.
-
-```Go
-	tk.Target.mergeObservations(targetResult.Observations)
-	tk.Control.mergeObservations(controlResult.Observations)
-
-```
-
 ### Return
 
 Finally, we can return, as the measurement ran successfully.

internal/tutorial/dslx/chapter02/main.go

@@ -106,21 +106,6 @@ type Subresult struct {
 	Cached        bool                                      `json:"-"`
 }
 
-// ```
-//
-// Subresult.mergeObservations merges the observations collected during
-// a measurement with the Subresult output data format.
-//
-// ```Go
-
-func (tk *Subresult) mergeObservations(obs []*dslx.Observations) {
-	for _, o := range obs {
-		tk.NetworkEvents = append(tk.NetworkEvents, o.NetworkEvents...)
-		tk.TCPConnect = append(tk.TCPConnect, o.TCPConnect...)
-		tk.TLSHandshakes = append(tk.TLSHandshakes, o.TLSHandshakes...)
-	}
-}
-
 // ```
 //
 // ## The Measurer
@@ -428,20 +413,6 @@ func (m *Measurer) Run(ctx context.Context, args *model.ExperimentArgs) error {
 		tk.Control.Failure = &failure
 	}
 
-	// ```
-	//
-	// The measurement result not only contains the potential error, but also
-	// observations that have been collected during each step of the measurement pipeline.
-	// Observations are for example network events like read and write operations,
-	// TLS handshakes, or DNS queries. We as experiment programmers are responsible for
-	// extracting these observations from the dslx measurement result and storing
-	// them in the `TestKeys`, which is precisely what `Subresult.mergeObservations`
-	// (implemented above) does.
-	//
-	// ```Go
-	tk.Target.mergeObservations(targetResult.Observations)
-	tk.Control.mergeObservations(controlResult.Observations)
-
 	// ```
 	//
 	// ### Return