[bugfix/frontend] Don't show replies to hidden parents; return 404 if no "main" thread (#3411)

internal/federation/dereferencing/status_permitted.go

@@ -235,7 +235,7 @@ func (d *Dereferencer) isPermittedReply(
 
 	// Status doesn't claim to be approved.
 	// Check interaction policy of inReplyTo
-	// to see if it doesn't require approval.
+	// to see what we need to do with it.
 	replyable, err := d.intFilter.StatusReplyable(ctx,
 		reply.Account,
 		inReplyTo,
@@ -260,35 +260,52 @@ func (d *Dereferencer) isPermittedReply(
 		)
 	}
 
-	// Reply is permitted according to the interaction
-	// policy set on the replied-to status (if any).
-
-	if !replyable.MatchedOnCollection() {
-		// If we didn't match on a collection,
-		// then we don't require an acceptIRI,
-		// and we don't need to send an Accept;
-		// just permit the reply full stop.
+	if replyable.Permitted() &&
+		!replyable.MatchedOnCollection() {
+		// Reply is permitted and match was *not* made
+		// based on inclusion in a followers/following
+		// collection. Just permit the reply full stop
+		// as no approval / accept URI is necessary.
 		return true, nil
 	}
 
-	// Reply is permitted, but match was made based
-	// on inclusion in a followers/following collection.
-	//
-	// If the status is ours, mark it as PreApproved
-	// so the processor knows to create and send out
-	// an Accept for it immediately.
-	if inReplyTo.IsLocal() {
+	// Reply is either permitted based on inclusion in a
+	// followers/following collection, *or* is permitted
+	// pending approval, though we know at this point
+	// that the status did not include an approvedBy URI.
+
+	if !inReplyTo.IsLocal() {
+		// If the replied-to status is remote, we should just
+		// drop this reply at this point, as we can't verify
+		// that the remote replied-to account approves it, and
+		// we can't verify the presence of a remote account
+		// in one of another remote account's collections.
+		//
+		// It's possible we'll get an Accept from the replied-
+		// to account later, and we can store this reply then.
+		return false, nil
+	}
+
+	// Replied-to status is ours, so the
+	// replied-to account is ours as well.
+
+	if replyable.MatchedOnCollection() {
+		// If permission was granted based on inclusion in
+		// a followers/following collection, pre-approve the
+		// reply, as we ourselves can validate presence of the
+		// replier in the appropriate collection. Pre-approval
+		// lets the processor know it should send out an Accept
+		// straight away on behalf of the replied-to account.
 		reply.PendingApproval = util.Ptr(true)
 		reply.PreApproved = true
 		return true, nil
 	}
 
-	// For replies to remote statuses, which matched
-	// on a followers/following collection, but did not
-	// include an acceptIRI, we should just drop it.
-	// It's possible we'll get an Accept for it later
-	// and we can check everything again.
-	return false, nil
+	// Reply just requires approval from the local account
+	// it replies to. Set PendingApproval so the processor
+	// knows to create a pending interaction request.
+	reply.PendingApproval = util.Ptr(true)
+	return true, nil
 }
 
 // unpermittedByParent marks the given reply as rejected

internal/processing/status/context.go

@@ -19,6 +19,7 @@
 
 import (
 	"context"
+	"errors"
 	"slices"
 	"strings"
 
@@ -402,6 +403,10 @@ func (p *Processor) WebContextGet(
 		// We should mark the next **VISIBLE**
 		// reply as the first reply.
 		markNextVisibleAsFirstReply bool
+
+		// Map of statuses that didn't pass visi
+		// checks and won't be shown via the web.
+		hiddenStatuses = make(map[string]struct{})
 	)
 
 	for idx, status := range wholeThread {
@@ -427,11 +432,16 @@ func (p *Processor) WebContextGet(
 			}
 		}
 
-		// Ensure status is actually
-		// visible to just anyone, and
-		// hide / don't include it if not.
+		// Ensure status is actually visible to just
+		// anyone, and hide / don't include it if not.
+		//
+		// Include a check to see if the parent status
+		// is hidden; if so, we shouldn't show the child
+		// as it leads to weird-looking threading where
+		// a status seems to reply to nothing.
+		_, parentHidden := hiddenStatuses[status.InReplyToID]
 		v, err := p.visFilter.StatusVisible(ctx, nil, status)
-		if err != nil || !v {
+		if err != nil || !v || parentHidden {
 			if !inReplies {
 				// Main thread entry hidden.
 				wCtx.ThreadHidden++
@@ -439,12 +449,15 @@ func (p *Processor) WebContextGet(
 				// Reply hidden.
 				wCtx.ThreadRepliesHidden++
 			}
+
+			hiddenStatuses[status.ID] = struct{}{}
 			continue
 		}
 
 		// Prepare visible status to add to thread context.
 		webStatus, err := p.converter.StatusToWebStatus(ctx, status)
 		if err != nil {
+			hiddenStatuses[status.ID] = struct{}{}
 			continue
 		}
 
@@ -512,9 +525,17 @@ func (p *Processor) WebContextGet(
 		wCtx.ThreadLength = threadLength
 	}
 
-	// Jot down number of hidden posts so template doesn't have to do it.
+	// Jot down number of "main" thread entries shown.
 	wCtx.ThreadShown = wCtx.ThreadLength - wCtx.ThreadHidden
 
+	// If there's no posts visible in the
+	// "main" thread we shouldn't show replies
+	// via the web as that's just weird.
+	if wCtx.ThreadShown < 1 {
+		const text = "no statuses visible in main thread"
+		return nil, gtserror.NewErrorNotFound(errors.New(text))
+	}
+
 	// Mark the last "main" visible status.
 	wCtx.Statuses[wCtx.ThreadShown-1].ThreadLastMain = true
 
@@ -523,7 +544,7 @@ func (p *Processor) WebContextGet(
 	// part of the "main" thread.
 	wCtx.ThreadReplies = threadLength - wCtx.ThreadLength
 
-	// Jot down number of hidden replies so template doesn't have to do it.
+	// Jot down number of "replies" shown.
 	wCtx.ThreadRepliesShown = wCtx.ThreadReplies - wCtx.ThreadRepliesHidden
 
 	// Return the finished context.

web/template/about.tmpl

@@ -91,7 +91,7 @@ Polls can have up to
                 <li><a href="#contact">Contact</a></li>
                 <li><a href="#features">Features</a></li>
                 <li><a href="#languages">Languages</a></li>
-                <li><a href="#signup">Register an Account on {{ .instance.Title -}}</li>
+                <li><a href="#signup">Register an Account on {{ .instance.Title -}}</a></li>
                 <li><a href="#rules">Rules</a></li>
                 <li><a href="#terms">Terms and Conditions</a></li>
                 <li><a href="#moderated-servers">Moderated Servers</a></li>