MergeTree: Fix segment-offset typing

packages/dds/matrix/src/handlecache.ts

@@ -82,10 +82,10 @@ export class HandleCache implements IVectorConsumer<Handle> {
 		const { vector } = this;
 
 		for (let pos = start; pos < end; pos++) {
-			const { segment, offset } = vector.getContainingSegment(pos);
-			const asPerm = segment as PermutationSegment;
 			// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-			handles.push(asPerm.start + offset!);
+			const { segment, offset } = vector.getContainingSegment(pos)!;
+			const asPerm = segment as PermutationSegment;
+			handles.push(asPerm.start + offset);
 		}
 	}
 

packages/dds/matrix/src/matrix.ts

@@ -465,10 +465,7 @@ export class SharedMatrix<T = any>
 		localSeq: number,
 	): LocalReferencePosition {
 		const segoff = vector.getContainingSegment(pos, undefined, localSeq);
-		assert(
-			segoff.segment !== undefined && segoff.offset !== undefined,
-			0x8b3 /* expected valid position */,
-		);
+		assert(segoff !== undefined, 0x8b3 /* expected valid position */);
 		return vector.createLocalReferencePosition(
 			segoff.segment,
 			segoff.offset,

packages/dds/matrix/src/permutationvector.ts

@@ -201,15 +201,16 @@ export class PermutationVector extends Client {
 		posToAdjust: number,
 		op: ISequencedDocumentMessage,
 	): { pos: number | undefined; handle: Handle } {
-		const { segment, offset } = this.getContainingSegment<PermutationSegment>(posToAdjust, {
+		const segOff = this.getContainingSegment<PermutationSegment>(posToAdjust, {
 			referenceSequenceNumber: op.referenceSequenceNumber,
 			clientId: op.clientId,
 		});
 
 		assert(
-			segment !== undefined && offset !== undefined,
+			segOff !== undefined,
 			0xbac /* segment must be available for operations in the collab window */,
 		);
+		const { segment, offset } = segOff;
 
 		if (segmentIsRemoved(segment)) {
 			// this case is tricky. the segment which the row or column data is remove
@@ -471,7 +472,7 @@ export function reinsertSegmentIntoVector(
 
 	// (Re)insert the removed number of rows at the original position.
 	const op = vector.insertSegmentLocal(pos, original);
-	const inserted = vector.getContainingSegment(pos).segment as PermutationSegment;
+	const inserted = vector.getContainingSegment(pos)?.segment as PermutationSegment;
 
 	// we reuse the original handle here
 	// so if cells exist, they can be found, and re-inserted

packages/dds/merge-tree/src/client.ts

@@ -878,17 +878,20 @@ export class Client extends TypedEventEmitter<IClientEvents> {
 		const useNewSlidingBehavior = true;
 		// Destructuring segment + offset is convenient and segment is reassigned
 		// eslint-disable-next-line prefer-const
-		let { segment: newSegment, offset: newOffset } = getSlideToSegoff(
+		const segOff = getSlideToSegoff(
 			{ segment: oldSegment, offset: oldOffset },
 			slidePreference,
 			reconnectingPerspective,
 			useNewSlidingBehavior,
 		);
 
-		newSegment ??=
-			slidePreference === SlidingPreference.FORWARD
-				? this._mergeTree.endOfTree
-				: this._mergeTree.startOfTree;
+		const { segment: newSegment, offset: newOffset } = segOff ?? {
+			segment:
+				slidePreference === SlidingPreference.FORWARD
+					? this._mergeTree.endOfTree
+					: this._mergeTree.startOfTree,
+			offset: 0,
+		};
 
 		assert(
 			isSegmentLeaf(newSegment) && newOffset !== undefined,
@@ -1612,10 +1615,12 @@ export class Client extends TypedEventEmitter<IClientEvents> {
 		pos: number,
 		sequenceArgs?: Pick<ISequencedDocumentMessage, "referenceSequenceNumber" | "clientId">,
 		localSeq?: number,
-	): {
-		segment: T | undefined;
-		offset: number | undefined;
-	} {
+	):
+		| {
+				segment: T;
+				offset: number;
+		  }
+		| undefined {
 		let perspective: Perspective;
 		const clientId =
 			sequenceArgs === undefined
@@ -1630,20 +1635,17 @@ export class Client extends TypedEventEmitter<IClientEvents> {
 			perspective = new PriorPerspective(refSeq, clientId);
 		}
 
-		return this._mergeTree.getContainingSegment(pos, perspective) as {
-			segment: T | undefined;
-			offset: number | undefined;
-		};
+		return this._mergeTree.getContainingSegment(pos, perspective) as
+			| {
+					segment: T;
+					offset: number;
+			  }
+			| undefined;
 	}
 
 	getPropertiesAtPosition(pos: number): PropertySet | undefined {
-		let propertiesAtPosition: PropertySet | undefined;
 		const segoff = this.getContainingSegment(pos);
-		const seg = segoff.segment;
-		if (seg) {
-			propertiesAtPosition = seg.properties;
-		}
-		return propertiesAtPosition;
+		return segoff?.segment?.properties;
 	}
 
 	getRangeExtentsOfPosition(pos: number): {
@@ -1654,7 +1656,7 @@ export class Client extends TypedEventEmitter<IClientEvents> {
 		let posAfterEnd: number | undefined;
 
 		const segoff = this.getContainingSegment(pos);
-		const seg = segoff.segment;
+		const seg = segoff?.segment;
 		if (seg) {
 			posStart = this.getPosition(seg);
 			posAfterEnd = posStart + seg.cachedLength;

packages/dds/merge-tree/src/mergeTree.ts

@@ -469,15 +469,17 @@ function getSlideToSegment(
  * @internal
  */
 export function getSlideToSegoff(
-	segoff: { segment: ISegmentInternal | undefined; offset: number | undefined },
+	segoff: { segment: ISegmentInternal; offset: number } | undefined,
 	slidingPreference: SlidingPreference = SlidingPreference.FORWARD,
 	perspective: Perspective = allAckedChangesPerspective,
 	useNewSlidingBehavior: boolean = false,
-): {
-	segment: ISegmentInternal | undefined;
-	offset: number | undefined;
-} {
-	if (!isSegmentLeaf(segoff.segment)) {
+):
+	| {
+			segment: ISegmentInternal;
+			offset: number;
+	  }
+	| undefined {
+	if (!isSegmentLeaf(segoff?.segment)) {
 		return segoff;
 	}
 	const [segment, _] = getSlideToSegment(
@@ -490,8 +492,11 @@ export function getSlideToSegoff(
 	if (segment === segoff.segment) {
 		return segoff;
 	}
-	const offset =
-		segment && segment.ordinal < segoff.segment.ordinal ? segment.cachedLength - 1 : 0;
+	if (segment === undefined) {
+		return undefined;
+	}
+
+	const offset = segment.ordinal < segoff.segment.ordinal ? segment.cachedLength - 1 : 0;
 	return {
 		segment,
 		offset,
@@ -849,10 +854,12 @@ export class MergeTree {
 	public getContainingSegment(
 		pos: number,
 		perspective: Perspective,
-	): {
-		segment: ISegmentLeaf | undefined;
-		offset: number | undefined;
-	} {
+	):
+		| {
+				segment: ISegmentLeaf;
+				offset: number;
+		  }
+		| undefined {
 		assert(
 			perspective.localSeq === undefined ||
 				perspective.clientId === this.collabWindow.clientId,
@@ -868,6 +875,9 @@ export class MergeTree {
 			return false;
 		};
 		this.nodeMap(perspective, leaf, undefined, pos, pos + 1);
+		if (segment === undefined || offset === undefined) {
+			return undefined;
+		}
 		return { segment, offset };
 	}
 
@@ -1260,10 +1270,11 @@ export class MergeTree {
 	): Marker | undefined {
 		let foundMarker: Marker | undefined;
 
-		const { segment } = this.getContainingSegment(startPos, this.localPerspective);
-		if (!isSegmentLeaf(segment)) {
+		const segoff = this.getContainingSegment(startPos, this.localPerspective);
+		if (!isSegmentLeaf(segoff?.segment)) {
 			return undefined;
 		}
+		const { segment } = segoff;
 
 		depthFirstNodeWalk(
 			segment.parent,
@@ -1529,7 +1540,7 @@ export class MergeTree {
 
 		if (isSegmentLeaf(segmentInfo?.segment)) {
 			const segmentPosition = this.getPosition(segmentInfo.segment, this.localPerspective);
-			return segmentPosition + segmentInfo.offset!;
+			return segmentPosition + segmentInfo.offset;
 		} else {
 			if (remoteClientPosition === this.getLength(remotePerspective)) {
 				return this.getLength(this.localPerspective);
@@ -2085,14 +2096,9 @@ export class MergeTree {
 		const createRefFromSequencePlace = (
 			place: InteriorSequencePlace,
 		): LocalReferencePosition => {
-			const { segment: placeSeg, offset: placeOffset } = this.getContainingSegment(
-				place.pos,
-				perspective,
-			);
-			assert(
-				isSegmentLeaf(placeSeg) && placeOffset !== undefined,
-				0xa3f /* segments cannot be undefined */,
-			);
+			const segOff = this.getContainingSegment(place.pos, perspective);
+			assert(isSegmentLeaf(segOff?.segment), 0xa3f /* segments cannot be undefined */);
+			const { segment: placeSeg, offset: placeOffset } = segOff;
 			return this.createLocalReferencePosition(
 				placeSeg,
 				placeOffset,

packages/dds/merge-tree/src/revertibles.ts

@@ -309,7 +309,7 @@ function revertLocalRemove(
 		const insertSegment = mergeTreeWithRevert.getContainingSegment(
 			realPos,
 			mergeTreeWithRevert.localPerspective,
-		).segment;
+		)?.segment;
 		assertSegmentLeaf(insertSegment);
 
 		const localSlideFilter = (lref: LocalReferencePosition): boolean =>

packages/dds/merge-tree/src/test/beastTest.spec.ts

@@ -374,7 +374,7 @@ export function mergeTreeTest1(): void {
 	checkInsertMergeTree(mergeTree, 4, makeCollabTextSegment("fi"));
 	mergeTree.mapRange(printTextSegment, localPerspective, undefined);
 	const segoff = mergeTree.getContainingSegment(4, mergeTree.localPerspective);
-	log(mergeTree.getPosition(segoff.segment!, mergeTree.localPerspective));
+	log(mergeTree.getPosition(segoff!.segment, mergeTree.localPerspective));
 	log(new MergeTreeTextHelper(mergeTree).getText(mergeTree.localPerspective));
 	log(mergeTree.toString());
 	TestPack().firstTest();
@@ -1502,7 +1502,7 @@ function findReplacePerf(filename: string): void {
 		const curSegOff = client.getContainingSegment<ISegmentPrivate>(pos);
 		cFetches++;
 
-		const curSeg = curSegOff.segment;
+		const curSeg = curSegOff?.segment;
 		const textSeg = <TextSegment>curSeg;
 		if (textSeg !== null) {
 			const text = textSeg.text;

packages/dds/merge-tree/src/test/client.annotateMarker.spec.ts

@@ -34,7 +34,7 @@ describe("TestClient", () => {
 			});
 			assert(insertOp);
 			const markerInfo = client.getContainingSegment<ISegmentPrivate>(0);
-			const marker = markerInfo.segment as Marker;
+			const marker = markerInfo?.segment as Marker;
 			const annotateOp = client.annotateMarker(marker, { foo: "bar" });
 			assert(annotateOp);
 			assert(marker.properties);