dslx: post-Func.Apply(Maybe[T])-introduction cleanups (ooni#1384)

This diff contains cleanups in dslx after we modified Func.Apply to take
a Maybe[T] as input:

- we don't need anymore to record the failed operation because we can
compute that inline, given that now we can write post-operation filters
that observe whether the operation failed or succeeded;

- likewise, we don't need to use counters anymore;

- likewise, we can remove functions to inspect the first error, because
we can compute that inline.

The reference issue is ooni/probe#2613.

internal/dslx/dns.go

@@ -9,7 +9,6 @@ import (
 	"time"
 
 	"github.com/ooni/probe-cli/v3/internal/logx"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 // DomainName is a domain name to resolve.
@@ -107,7 +106,6 @@ func DNSLookupGetaddrinfo(rt Runtime) Func[*DomainToResolve, *ResolvedAddresses]
 		return &Maybe[*ResolvedAddresses]{
 			Error:        err,
 			Observations: maybeTraceToObservations(trace),
-			Operation:    netxlite.ResolveOperation,
 			State:        state,
 		}
 	})
@@ -156,7 +154,6 @@ func DNSLookupUDP(rt Runtime, endpoint string) Func[*DomainToResolve, *ResolvedA
 		return &Maybe[*ResolvedAddresses]{
 			Error:        err,
 			Observations: maybeTraceToObservations(trace),
-			Operation:    netxlite.ResolveOperation,
 			State:        state,
 		}
 	})

internal/dslx/fxcore.go

@@ -6,9 +6,7 @@ package dslx
 
 import (
 	"context"
-	"sync/atomic"
 
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
 	"github.com/ooni/probe-cli/v3/internal/runtimex"
 )
 
@@ -26,7 +24,6 @@ func (op Operation[A, B]) Apply(ctx context.Context, a *Maybe[A]) *Maybe[B] {
 		return &Maybe[B]{
 			Error:        a.Error,
 			Observations: a.Observations,
-			Operation:    a.Operation,
 			State:        *new(B), // zero value
 		}
 	}
@@ -42,9 +39,6 @@ type Maybe[State any] struct {
 	// Observations contains the collected observations.
 	Observations []*Observations
 
-	// Operation contains the name of this operation.
-	Operation string
-
 	// State contains state passed between function calls. You should
 	// only access State when Error is nil and Skipped is false.
 	State State
@@ -55,7 +49,6 @@ func NewMaybeWithValue[State any](value State) *Maybe[State] {
 	return &Maybe[State]{
 		Error:        nil,
 		Observations: []*Observations{},
-		Operation:    "",
 		State:        value,
 	}
 }
@@ -83,81 +76,16 @@ func (h *compose2Func[A, B, C]) Apply(ctx context.Context, a *Maybe[A]) *Maybe[C
 		return &Maybe[C]{
 			Error:        mb.Error,
 			Observations: mb.Observations,
-			Operation:    mb.Operation,
 			State:        *new(C), // zero value
 		}
 	}
 
 	mc := h.g.Apply(ctx, mb)
 	runtimex.Assert(mc != nil, "h.g.Apply returned a nil pointer")
 
-	op := mc.Operation
-	if op == "" { // propagate the previous operation name, if this operation has none
-		op = mb.Operation
-	}
 	return &Maybe[C]{
 		Error:        mc.Error,
 		Observations: append(mb.Observations, mc.Observations...), // merge observations
-		Operation:    op,
 		State:        mc.State,
 	}
 }
-
-// NewCounter generates an instance of *Counter
-func NewCounter[T any]() *Counter[T] {
-	return &Counter[T]{}
-}
-
-// Counter allows to count how many times
-// a Func[T, *Maybe[T]] is invoked.
-type Counter[T any] struct {
-	n atomic.Int64
-}
-
-// Value returns the counter's value.
-func (c *Counter[T]) Value() int64 {
-	return c.n.Load()
-}
-
-// Func returns a Func[T, *Maybe[T]] that updates the counter.
-func (c *Counter[T]) Func() Func[T, T] {
-	return Operation[T, T](func(ctx context.Context, value T) *Maybe[T] {
-		c.n.Add(1)
-		return &Maybe[T]{
-			Error:        nil,
-			Observations: nil,
-			Operation:    "", // we cannot fail, so no need to store operation name
-			State:        value,
-		}
-	})
-}
-
-// FirstErrorExcludingBrokenIPv6Errors returns the first error and failed operation in a list of
-// *Maybe[T] excluding errors known to be linked with IPv6 issues.
-func FirstErrorExcludingBrokenIPv6Errors[T any](entries ...*Maybe[T]) (string, error) {
-	for _, entry := range entries {
-		if entry.Error == nil {
-			continue
-		}
-		err := entry.Error
-		switch err.Error() {
-		case netxlite.FailureNetworkUnreachable, netxlite.FailureHostUnreachable:
-			// This class of errors is often times linked with wrongly
-			// configured IPv6, therefore we skip them.
-		default:
-			return entry.Operation, err
-		}
-	}
-	return "", nil
-}
-
-// FirstError returns the first error and failed operation in a list of *Maybe[T].
-func FirstError[T any](entries ...*Maybe[T]) (string, error) {
-	for _, entry := range entries {
-		if entry.Error == nil {
-			continue
-		}
-		return entry.Operation, entry.Error
-	}
-	return "", nil
-}

internal/dslx/fxcore_test.go

@@ -31,7 +31,6 @@ func (f *fn) Apply(ctx context.Context, i *Maybe[int]) *Maybe[int] {
 				NetworkEvents: []*model.ArchivalNetworkEvent{{Tags: []string{"apply"}}},
 			},
 		},
-		Operation: f.name,
 	}
 }
 
@@ -52,7 +51,6 @@ func TestStageAdapter(t *testing.T) {
 		input := &Maybe[*DomainToResolve]{
 			Error:        errors.New("mocked error"),
 			Observations: []*Observations{},
-			Operation:    "",
 			State:        nil,
 		}
 
@@ -92,9 +90,6 @@ func TestCompose2(t *testing.T) {
 				if r.Error != tt.err {
 					t.Fatalf("unexpected error")
 				}
-				if tt.err != nil && r.Operation != "maybe fail" {
-					t.Fatalf("unexpected operation string")
-				}
 				if len(r.Observations) != tt.numObs {
 					t.Fatalf("unexpected number of (merged) observations")
 				}
@@ -115,9 +110,6 @@ func TestGen(t *testing.T) {
 		if r.State != 14 {
 			t.Fatalf("unexpected result state")
 		}
-		if r.Operation != "succeed" {
-			t.Fatal("unexpected operation string")
-		}
 	})
 }
 
@@ -137,104 +129,3 @@ func TestObservations(t *testing.T) {
 		}
 	})
 }
-
-/*
-Test cases:
-- Success counter:
-  - pipeline succeeds
-  - pipeline fails
-*/
-func TestCounter(t *testing.T) {
-	t.Run("Success counter", func(t *testing.T) {
-		tests := map[string]struct {
-			err    error
-			expect int64
-		}{
-			"pipeline succeeds": {err: nil, expect: 1},
-			"pipeline fails":    {err: errors.New("mocked"), expect: 0},
-		}
-		for name, tt := range tests {
-			t.Run(name, func(t *testing.T) {
-				fn := getFn(tt.err, "maybe fail")
-				cnt := NewCounter[int]()
-				composit := Compose2(fn, cnt.Func())
-				r := composit.Apply(context.Background(), NewMaybeWithValue(42))
-				cntVal := cnt.Value()
-				if cntVal != tt.expect {
-					t.Fatalf("unexpected counter value")
-				}
-				if r.Operation != "maybe fail" {
-					t.Fatal("unexpected operation string")
-				}
-			})
-		}
-	})
-}
-
-/*
-Test cases:
-- Extract first error from list of *Maybe:
-  - without errors
-  - with errors
-
-- Extract first error excluding broken IPv6 errors:
-  - without errors
-  - with errors
-*/
-func TestFirstError(t *testing.T) {
-	networkUnreachable := errors.New(netxlite.FailureNetworkUnreachable)
-	mockErr := errors.New("mocked")
-	errRes := []*Maybe[string]{
-		{Error: nil, Operation: "succeeds"},
-		{Error: networkUnreachable, Operation: "broken IPv6"},
-		{Error: mockErr, Operation: "mock error"},
-	}
-	noErrRes := []*Maybe[int64]{
-		{Error: nil, Operation: "succeeds"},
-		{Error: nil, Operation: "succeeds"},
-	}
-
-	t.Run("Extract first error from list of *Maybe", func(t *testing.T) {
-		t.Run("without errors", func(t *testing.T) {
-			failedOp, firstErr := FirstError(noErrRes...)
-			if firstErr != nil {
-				t.Fatalf("unexpected error: %s", firstErr)
-			}
-			if failedOp != "" {
-				t.Fatalf("unexpected failed operation")
-			}
-		})
-
-		t.Run("with errors", func(t *testing.T) {
-			failedOp, firstErr := FirstError(errRes...)
-			if firstErr != networkUnreachable {
-				t.Fatalf("unexpected error: %s", firstErr)
-			}
-			if failedOp != "broken IPv6" {
-				t.Fatalf("unexpected failed operation")
-			}
-		})
-	})
-
-	t.Run("Extract first error excluding broken IPv6 errors", func(t *testing.T) {
-		t.Run("without errors", func(t *testing.T) {
-			failedOp, firstErrExclIPv6 := FirstErrorExcludingBrokenIPv6Errors(noErrRes...)
-			if firstErrExclIPv6 != nil {
-				t.Fatalf("unexpected error: %s", firstErrExclIPv6)
-			}
-			if failedOp != "" {
-				t.Fatalf("unexpected failed operation")
-			}
-		})
-
-		t.Run("with errors", func(t *testing.T) {
-			failedOp, firstErrExclIPv6 := FirstErrorExcludingBrokenIPv6Errors(errRes...)
-			if firstErrExclIPv6 != mockErr {
-				t.Fatalf("unexpected error: %s", firstErrExclIPv6)
-			}
-			if failedOp != "mock error" {
-				t.Fatalf("unexpected failed operation")
-			}
-		})
-	})
-}

internal/dslx/httpcore.go

@@ -151,7 +151,6 @@ func HTTPRequest(rt Runtime, options ...HTTPRequestOption) Func[*HTTPConnection,
 		return &Maybe[*HTTPResponse]{
 			Error:        err,
 			Observations: observations,
-			Operation:    netxlite.HTTPRoundTripOperation,
 			State:        state,
 		}
 	})

internal/dslx/httpquic.go

@@ -37,7 +37,6 @@ func HTTPConnectionQUIC(rt Runtime) Func[*QUICConnection, *HTTPConnection] {
 		return &Maybe[*HTTPConnection]{
 			Error:        nil,
 			Observations: nil,
-			Operation:    "", // we cannot fail, so no need to store operation name
 			State:        state,
 		}
 	})

internal/dslx/httptcp.go

@@ -38,7 +38,6 @@ func HTTPConnectionTCP(rt Runtime) Func[*TCPConnection, *HTTPConnection] {
 		return &Maybe[*HTTPConnection]{
 			Error:        nil,
 			Observations: nil,
-			Operation:    "", // we cannot fail, so no need to store operation name
 			State:        state,
 		}
 	})

internal/dslx/httptls.go

@@ -38,7 +38,6 @@ func HTTPConnectionTLS(rt Runtime) Func[*TLSConnection, *HTTPConnection] {
 		return &Maybe[*HTTPConnection]{
 			Error:        nil,
 			Observations: nil,
-			Operation:    "", // we cannot fail, so no need to store operation name
 			State:        state,
 		}
 	})

internal/dslx/quic.go

@@ -70,7 +70,6 @@ func QUICHandshake(rt Runtime, options ...TLSHandshakeOption) Func[*Endpoint, *Q
 		return &Maybe[*QUICConnection]{
 			Error:        err,
 			Observations: maybeTraceToObservations(trace),
-			Operation:    netxlite.QUICHandshakeOperation,
 			State:        state,
 		}
 	})

internal/dslx/tcp.go

@@ -10,7 +10,6 @@ import (
 	"time"
 
 	"github.com/ooni/probe-cli/v3/internal/logx"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 // TCPConnect returns a function that establishes TCP connections.
@@ -55,7 +54,6 @@ func TCPConnect(rt Runtime) Func[*Endpoint, *TCPConnection] {
 		return &Maybe[*TCPConnection]{
 			Error:        err,
 			Observations: maybeTraceToObservations(trace),
-			Operation:    netxlite.ConnectOperation,
 			State:        state,
 		}
 	})

internal/dslx/tls.go

@@ -95,7 +95,6 @@ func TLSHandshake(rt Runtime, options ...TLSHandshakeOption) Func[*TCPConnection
 		return &Maybe[*TLSConnection]{
 			Error:        err,
 			Observations: maybeTraceToObservations(trace),
-			Operation:    netxlite.TLSHandshakeOperation,
 			State:        state,
 		}
 	})