(core) updates from grist-core

app/client/components/BaseView.js

@@ -132,7 +132,7 @@ function BaseView(gristDoc, viewSectionModel, options) {
   // Update the cursor whenever linkedRowId() changes (but only if we have any linking).
   this.autoDispose(this.linkedRowId.subscribe(rowId => {
     if (this.viewSection.linkingState.peek()) {
-      this.setCursorPos({rowId: rowId || 'new'});
+      this.setCursorPos({rowId: rowId || 'new'}, true);
     }
   }));
 
@@ -282,14 +282,14 @@ BaseView.prototype.deleteRecords = function(source) {
 
 /**
  * Sets the cursor to the given position, deferring if necessary until the current query finishes
- * loading.
+ * loading. isFromLink will be set when called as result of cursor linking(see Cursor.setCursorPos for info)
  */
-BaseView.prototype.setCursorPos = function(cursorPos) {
+BaseView.prototype.setCursorPos = function(cursorPos, isFromLink = false) {
   if (this.isDisposed()) {
     return;
   }
   if (!this._isLoading.peek()) {
-    this.cursor.setCursorPos(cursorPos);
+    this.cursor.setCursorPos(cursorPos, isFromLink);
   } else {
     // This is the first step; the second happens in onTableLoaded.
     this._pendingCursorPos = cursorPos;

app/client/components/Cursor.ts

@@ -16,6 +16,26 @@ function nullAsUndefined<T>(value: T|null|undefined): T|undefined {
   return value == null ? undefined : value;
 }
 
+// ================ SequenceNum: used to keep track of cursor edits (lastEditedAt)
+// Basically just a global auto-incrementing counter, with some types to make intent more clear
+// Cursors are constructed at SequenceNEVER (0). After that, changes to their sequenceNum will go through
+// NextSequenceNum(), so they'll have unique, monotonically increasing numbers for their lastEditedAt()
+// NOTE: (by the time the page loads they'll already be at nonzero numbers, the never is intended to be transient)
+export type SequenceNum = number;
+export const SequenceNEVER: SequenceNum = 0; // Cursors will start here
+let latestGlobalSequenceNum = SequenceNEVER;
+function nextSequenceNum() { // First call to this func should return 1
+  latestGlobalSequenceNum++;
+  return latestGlobalSequenceNum;
+}
+
+// NOTE: If latestGlobalSequenceNum overflows, I think it would stop incrementing because of floating point imprecision
+// However, we don't need to worry about overflow because:
+//   - Number.MAX_SAFE_INTEGER is 9,007,199,254,740,991 (9 * 10^15)
+//   - even at 1000 cursor-edits per second, it would take ~300,000 yrs to overflow
+//   - Plus it's client-side, so that's a single continuous 300-millenia-long session, which would be impressive uptime
+
+
 /**
  * Cursor represents the location of the cursor in the viewsection. It is maintained by BaseView,
  * and implements the shared functionality related to the cursor cell.
@@ -63,6 +83,14 @@ export class Cursor extends Disposable {
 
   private _properRowId: ko.Computed<UIRowId|null>;
 
+  // lastEditedAt is updated on _properRowId or fieldIndex update (including through setCursorPos)
+  // Used to determine which section takes priority for cursorLinking (specifically cycles/bidirectional linking)
+  private _lastEditedAt: ko.Observable<SequenceNum>;
+  // _silentUpdatesFlag prevents lastEditedAt from being updated, when a change in cursorPos isn't driven by the user.
+  // It's used when cursor linking calls setCursorPos, so that linked cursor moves don't trample lastEditedAt.
+  // WARNING: the flag approach relies on ko observables being resolved synchronously, may break if changed to grainjs?
+  private _silentUpdatesFlag: boolean = false;
+
   constructor(baseView: BaseView, optCursorPos?: CursorPos) {
     super();
     optCursorPos = optCursorPos || {};
@@ -83,6 +111,7 @@ export class Cursor extends Disposable {
     }));
 
     this.fieldIndex = baseView.viewSection.viewFields().makeLiveIndex(optCursorPos.fieldIndex || 0);
+
     this.autoDispose(commands.createGroup(Cursor.editorCommands, this, baseView.viewSection.hasFocus));
 
     // RowId might diverge from the one stored in _rowId when the data changes (it is filtered out). So here
@@ -93,8 +122,22 @@ export class Cursor extends Disposable {
       return rowId;
     }));
 
-    // Update the section's activeRowId when the cursor's rowIndex is changed.
+    this._lastEditedAt = ko.observable(SequenceNEVER);
+
+    // update the section's activeRowId and lastCursorEdit when needed
     this.autoDispose(this._properRowId.subscribe((rowId) => baseView.viewSection.activeRowId(rowId)));
+    this.autoDispose(this._lastEditedAt.subscribe((seqNum) => baseView.viewSection.lastCursorEdit(seqNum)));
+
+    // Update the cursor edit time if either the row or column change
+    // IMPORTANT: need to subscribe AFTER the properRowId->activeRowId subscription.
+    //  (Cursor-linking observables depend on lastCursorEdit, but only peek at activeRowId. Therefore, updating the
+    //   edit time triggers a re-read of activeRowId, and swapping the order will read stale values for rowId)
+    // NOTE: this may update sequence number twice for a single edit, but this shouldn't cause any issues.
+    //       For determining priority, this cursor will become the latest edited whether we call it once or twice.
+    //       For updating observables, the double-update might cause cursor-linking observables in LinkingState to
+    //       double-update, but it should be transient and get resolved immediately.
+    this.autoDispose(this._properRowId.subscribe(() => { this._cursorEdited(); }));
+    this.autoDispose(this.fieldIndex.subscribe(() => { this._cursorEdited(); }));
 
     // On dispose, save the current cursor position to the section model.
     this.onDispose(() => { baseView.viewSection.lastCursorPos = this.getCursorPos(); });
@@ -116,9 +159,17 @@ export class Cursor extends Disposable {
   /**
    * Moves the cursor to the given position. Only moves the row if rowId or rowIndex is valid,
    * preferring rowId.
+   *
+   * isFromLink prevents lastEditedAt from being updated, so lastEdit reflects only user-driven edits
    * @param cursorPos: Position as { rowId?, rowIndex?, fieldIndex? }, as from getCursorPos().
+   * @param isFromLink: should be set if this is a cascading update from cursor-linking
    */
-  public setCursorPos(cursorPos: CursorPos): void {
+  public setCursorPos(cursorPos: CursorPos, isFromLink: boolean = false): void {
+
+    try {
+      // If updating as a result of links, we want to NOT update lastEditedAt
+      if (isFromLink) { this._silentUpdatesFlag = true; }
+
       if (cursorPos.rowId !== undefined && this.viewData.getRowIndex(cursorPos.rowId) >= 0) {
         this.rowIndex(this.viewData.getRowIndex(cursorPos.rowId));
       } else if (cursorPos.rowIndex !== undefined && cursorPos.rowIndex >= 0) {
@@ -127,12 +178,46 @@ export class Cursor extends Disposable {
         // Write rowIndex to itself to force an update of rowId if needed.
         this.rowIndex(this.rowIndex.peek());
       }
+
       if (cursorPos.fieldIndex !== undefined) {
         this.fieldIndex(cursorPos.fieldIndex);
       }
+
+      // NOTE: _cursorEdited
+      // We primarily update cursorEdited counter from a this._properRowId.subscribe(), since that catches updates
+      //   from many sources (setCursorPos, arrowKeys, save/load, filter/sort-changes, etc)
+      // However, there's some cases where we user touches a section and properRowId doesn't change. Obvious one is
+      //   clicking in a section on the cell the cursor is already on. This doesn't change the cursor position, but it
+      //   SHOULD still update cursors to use that section as most up-to-date (user just clicked on a cell!), so we do
+      //   it here. (normally is minor issue, but can matter when a section has rows filtered out so cursors desync)
+      // Also a more subtle case: when deleting a row with several sections linked together, properRowId can fail to
+      //   update. When GridView.deleteRows calls setCursorPos to keep cursor from jumping after delete, the observable
+      //   doesn't trigger cursorEdited(), because (I think) _properRowId has already been updated that cycle.
+      //   This caused a bug when several viewSections were cursor-linked to each other and a row was deleted
+      // NOTE: Calling it explicitly here will cause cursorEdited to be called twice sometimes,
+      //   but that shouldn't cause any problems, since we don't care about edit counts, just who was edited latest.
+      this._cursorEdited();
+
+    } finally { // Make sure we reset this even on error
+      this._silentUpdatesFlag = false;
     }
 
+  }
+
+
+
+
   public setLive(isLive: boolean): void {
     this._isLive(isLive);
   }
+
+  // Should be called whenever the cursor is updated
+  // EXCEPT FOR: when cursor is set by linking
+  // this is used to determine which widget/cursor has most recently been touched,
+  // and therefore which one should be used to drive linking if there's a conflict
+  private _cursorEdited(): void {
+    // If updating as a result of links, we want to NOT update lastEdited
+    if (!this._silentUpdatesFlag)
+      { this._lastEditedAt(nextSequenceNum()); }
+  }
 }

app/client/components/GristDoc.ts

@@ -1129,7 +1129,8 @@ export class GristDoc extends DisposableWithEvents {
   public async recursiveMoveToCursorPos(
     cursorPos: CursorPos,
     setAsActiveSection: boolean,
-    silent: boolean = false): Promise<boolean> {
+    silent: boolean = false,
+    visitedSections: number[] = []): Promise<boolean> {
     try {
       if (!cursorPos.sectionId) {
         throw new Error('sectionId required');
@@ -1141,6 +1142,12 @@ export class GristDoc extends DisposableWithEvents {
       if (!section.id.peek()) {
         throw new Error(`Section ${cursorPos.sectionId} does not exist`);
       }
+
+      if (visitedSections.includes(section.id.peek())) {
+        // We've already been here (we hit a cycle), just return immediately
+        return true;
+      }
+
       const srcSection = section.linkSrcSection.peek();
       if (srcSection.id.peek()) {
         // We're in a linked section, so we need to recurse to make sure the row we want
@@ -1190,7 +1197,7 @@ export class GristDoc extends DisposableWithEvents {
         await this.recursiveMoveToCursorPos({
           rowId: srcRowId,
           sectionId: srcSection.id.peek(),
-        }, false, silent);
+        }, false, silent, visitedSections.concat([section.id.peek()]));
       }
       const view: ViewRec = section.view.peek();
       const docPage: ViewDocPage = section.isRaw.peek() ? "data" : view.getRowId();

app/client/components/LinkingState.ts

@@ -1,3 +1,4 @@
+import {SequenceNEVER, SequenceNum} from "app/client/components/Cursor";
 import {DataRowModel} from "app/client/models/DataRowModel";
 import DataTableModel from "app/client/models/DataTableModel";
 import {DocModel} from 'app/client/models/DocModel';
@@ -51,7 +52,12 @@ export const EmptyFilterColValues: FilterColValues = FilterStateToColValues(Empt
 export class LinkingState extends Disposable {
   // If linking affects target section's cursor, this will be a computed for the cursor rowId.
   // Is undefined if not cursor-linked
-  public readonly cursorPos?: ko.Computed<UIRowId>;
+  public readonly cursorPos?: ko.Computed<UIRowId|null>;
+
+  // Cursor-links can be cyclic, need to keep track of both rowId and the lastCursorEdit that it came from to
+  // resolve it correctly, (use just one observable so they update at the same time)
+  //NOTE: observables don't do deep-equality check, so need to replace the whole array when updating
+  public readonly incomingCursorPos: ko.Computed<[UIRowId|null, SequenceNum]>;
 
   // If linking affects filtering, this is a computed for the current filtering state, including user-facing
   // labels for filter values and types of the filtered columns
@@ -194,13 +200,120 @@ export class LinkingState extends Disposable {
       //        either same-table cursor-link (!srcCol && !tgtCol, so do activeRowId -> cursorPos)
       //        or cursor-link by reference   ( srcCol && !tgtCol, so do srcCol -> cursorPos)
 
-      //colVal, or rowId if no srcCol
+      // Cursor linking notes:
+      //
+      // If multiple viewSections are cursor-linked together A->B->C, we need to propagate the linked cursorPos along.
+      // The old way was to have: A.activeRowId -> (sets by cursor-link) -> B.activeRowId, and so on
+      //                                                                                                               |
+      //                                   -->  [B.LS]                    --> [C.LS]                                   |
+      //                                  /        | B.LS.cursorPos      /       | C.LS.cursorPos                      |
+      //                                 /         v                    /        v                                     |
+      //                   [ A ]--------/        [ B ]   --------------/       [ C ]                                   |
+      //                        A.actRowId                B.actRowId                                                   |
+      //
+      // However, if e.g. viewSec B is filtered, the correct rowId might not exist in B, and so its activeRowId would be
+      // on a different row, and therefore the cursor linking would set C to a different row from A, even if it existed
+      // in C
+      //
+      // Normally this wouldn't be too bad, but to implement bidirectional linking requires allowing cycles of
+      // cursor-links, in which case this behavior becomes extra-problematic, both in being more unexpected from a UX
+      // perspective and because a section will eventually be linked to itself, which is an unstable loop.
+      //
+      // A better solution is to propagate the linked rowId directly through the chain of linkingStates without passing
+      // through the activeRowIds of the sections, so whether a section is filtered or not doesn't affect propagation.
+      //
+      //                                                B.LS.incCursPos                                                |
+      //                                 -->  [B.LS]   -------------->   [C.LS]                                        |
+      //                                /        |                          |                                          |
+      //                               /         v B.LS.cursorPos           v C.LS.cursorPos                           |
+      //                 [ A ]--------/        [ B ]                      [ C ]                                        |
+      //                      A.actRowId                                                                               |
+      //
+      // If the previous section has a linkingState, we use the previous LS's incomingCursorPos
+      // (i.e. two sections back) instead of looking at our srcSection's activeRowId. This way it doesn't matter how
+      // section B is filtered, since we're getting our cursorPos straight from A (through a computed in B.LS)
+      //
+      // However, each linkingState needs to decide whether to use the cursorPos from the srcSec (i.e. its activeRowId),
+      // or to use the previous linkState's incomingCursorPos. We want to use whichever section the user most recently
+      // interacted with, i.e. whichever cursor update was most recent. For this we use, the cursor version (given in
+      // viewSection.lastCursorEdit). incomingCursorPos is a pair of [rowId, sequenceNum], so each linkingState sets its
+      // incomingCursorPos to whichever is most recent between its srcSection, and the previous LS's incCursPos.
+      //
+      // If we do this right, the end result is that because the lastCursorEdits are guaranteed to be unique,
+      // there is always a stable configuration of links, where even in the case of a cycle the incomingCursorPos-es
+      // will all take their rowId and version from the most recently edited viewSection in the cycle,
+      // which is what the user expects
+      //
+      //               ...from C--> [A.LS] -------->  [B.LS]               --> [C.LS] ----->...to A                    |
+      //                               |                 |                /       |                                    |
+      //                               v                 v               /        v                                    |
+      //                             [ A ]             [ B ]   ---------/       [ C ]                                  |
+      //                                          (most recently edited)                                               |
+      //
+      // Once the incomingCursorPos-es are determined correctly, the cursorPos-es just need to pull out the rowId,
+      // and that will drive the cursors of the associated tgt section for each LS.
+      //
+      // NOTE: setting cursorPos *WILL* change the viewSections' cursor, but it's special-cased to
+      // so that cursor-driven linking doesn't modify their lastCursorEdit times, so that lastCursorEdit
+      // reflects only changes driven by external factors
+      // (e.g. page load, user moving cursor, user changing linking settings/filter settings)
+      // =============================
+
+      // gets the relevant col value for the passed-in rowId, or return rowId unchanged if same-table link
       const srcValueFunc = this._makeValGetter(this._srcSection.table(), this._srcColId);
 
-      if (srcValueFunc) { // if makeValGetter succeeded, set up cursorPos
+      // check for failure
-        this.cursorPos = this.autoDispose(ko.computed(() =>
+      if (srcValueFunc) {
-          srcValueFunc(srcSection.activeRowId()) as UIRowId
+        //Incoming-cursor-pos determines what the linked cursor position should be, considering the previous
-        ));
+        //linked section (srcSection) and all upstream sections (through srcSection.linkingState)
+        this.incomingCursorPos = this.autoDispose((ko.computed(() => {
+          // NOTE: This computed primarily decides between srcSec and prevLink. Here's what those mean:
+          // e.g. consider sections A->B->C, (where this === C)
+          // We need to decide between taking cursor info from B, our srcSection (1 hop back)
+          //    vs taking cursor info from further back, e.g. A, or before (2+ hops back)
+          // To take cursor info from further back, we rely on B's linkingState, since B's linkingState will
+          //    be looking at the preceding sections, either A or whatever is behind A.
+          // Therefore: we either use srcSection (1 back), or prevLink = srcSection.linkingState (2+ back)
+
+          // Get srcSection's info (1 hop back)
+          const srcSecPos = this._srcSection.activeRowId.peek(); //we don't depend on this, only on its cursor version
+          const srcSecVersion = this._srcSection.lastCursorEdit();
+
+          // If cursors haven't been initialized, cursor-linking doesn't make sense, so don't do it
+          if(srcSecVersion === SequenceNEVER) {
+            return [null, SequenceNEVER] as [UIRowId|null, SequenceNum];
+          }
+
+          // Get previous linkingstate's info, if applicable (2 or more hops back)
+          const prevLink = this._srcSection.linkingState?.();
+          const prevLinkHasCursor = prevLink &&
+            (prevLink.linkTypeDescription() === "Cursor:Same-Table" ||
+              prevLink.linkTypeDescription() === "Cursor:Reference");
+          const [prevLinkedPos, prevLinkedVersion] = prevLinkHasCursor ? prevLink.incomingCursorPos() :
+            [null, SequenceNEVER];
+
+          // ==== Determine whose info to use:
+          // If prevLinkedVersion < srcSecVersion, then the prev linked data is stale, don't use it
+          // If prevLinkedVersion == srcSecVersion, then srcSec is the driver for this link cycle (i.e. we're its first
+          //                                        outgoing link), AND the link cycle has come all the way around
+          const usePrev = prevLinkHasCursor && prevLinkedVersion > srcSecVersion;
+
+          // srcSec/prevLinkedPos is rowId from srcSec. However if "Cursor:Reference", we must follow the ref in srcCol
+          // srcValueFunc will get the appropriate value based on this._srcColId if that's the case
+          const tgtCursorPos = (srcValueFunc(usePrev ? prevLinkedPos : srcSecPos) || "new") as UIRowId;
+          // NOTE: srcValueFunc returns 'null' if rowId is the add-row, so we coerce that back into || "new"
+          // NOTE: cursor linking is only ever done by the id column (for same-table) or by single Ref col (cursor:ref),
+          //     so we'll never have to worry about `null` showing up as an actual cell-value. (A blank Ref is just `0`)
+
+          return [
+              tgtCursorPos,
+              usePrev ? prevLinkedVersion : srcSecVersion, //propagate which version our cursorPos is from
+          ] as [UIRowId|null, SequenceNum];
+        })));
+
+        // Pull out just the rowId from incomingCursor Pos
+        // (This get applied directly to tgtSection's cursor),
+        this.cursorPos = this.autoDispose(ko.computed(() => this.incomingCursorPos()[0]));
       }
 
       if (!srcColId) { // If same-table cursor-link, copy getDefaultColValues from the source if possible
@@ -210,6 +323,8 @@ export class LinkingState extends Disposable {
         }
       }
     }
+    // ======= End of cursor linking
+
 
     // Make filterColValues, which is just the filtering-relevant parts of filterState
     // (it's used in places that don't need the user-facing labels, e.g. CSV export)

app/client/models/entities/ViewSectionRec.ts

@@ -1,4 +1,5 @@
 import BaseView from 'app/client/components/BaseView';
+import {SequenceNEVER, SequenceNum} from 'app/client/components/Cursor';
 import {EmptyFilterColValues, LinkingState} from 'app/client/components/LinkingState';
 import {KoArray} from 'app/client/lib/koArray';
 import {ColumnToMapImpl} from 'app/client/models/ColumnToMap';
@@ -155,6 +156,8 @@ export interface ViewSectionRec extends IRowModel<"_grist_Views_section">, RuleO
 
   activeRowId: ko.Observable<UIRowId | null>;     // May be null when there are no rows.
 
+  lastCursorEdit: ko.Observable<SequenceNum>;
+
   // If the view instance for section is instantiated, it will be accessible here.
   viewInstance: ko.Observable<BaseView | null>;
 
@@ -627,6 +630,7 @@ export function createViewSectionRec(this: ViewSectionRec, docModel: DocModel):
   this.linkTargetCol = refRecord(docModel.columns, this.linkTargetColRef);
 
   this.activeRowId = ko.observable<UIRowId|null>(null);
+  this.lastCursorEdit = ko.observable<SequenceNum>(SequenceNEVER);
 
   this._linkingState = Holder.create(this);
   this.linkingState = this.autoDispose(ko.pureComputed(() => {

app/client/ui/RightPanel.ts

@@ -643,7 +643,13 @@ export class RightPanel extends Disposable {
       const lstate = use(tgtSec.linkingState);
       const lfilter = lstate?.filterState ? use(lstate.filterState) : undefined;
 
-      const cursorPosStr = lstate?.cursorPos ? `${tgtSec.tableId()}[${use(lstate.cursorPos)}]` : "N/A";
+      // Debug info for cursor linking
+      const inPos = lstate?.incomingCursorPos ? use(lstate.incomingCursorPos) : null;
+      const cursorPosStr = (lstate?.cursorPos ? `${use(tgtSec.tableId)}[${use(lstate.cursorPos)}]` : "N/A") +
+      // TODO: the lastEdited and incomingCursorPos is kinda technical, to do with how bidirectional linking determines
+      //       priority for cyclical cursor links. Might be too technical even for the "advanced info" box
+        `\n srclastEdited: T+${use(srcSec.lastCursorEdit)} \n tgtLastEdited: T+${use(tgtSec.lastCursorEdit)}` +
+        `\n incomingCursorPos: ${inPos ? `${inPos[0]}@T+${inPos[1]}` : "N/A"}`;
 
       //Main link info as a big string, will be in a <pre></pre> block
       let preString = "No Incoming Link";

app/client/ui/selectBy.ts

@@ -49,8 +49,15 @@ interface LinkNode {
   groupbyColumns?: Set<number>;
 
   // list of ids of the sections that are ancestors to this section according to the linked section
-  // relationship
+  // relationship. ancestors[0] is this.section, ancestors[length-1] is oldest ancestor
-  ancestors: Set<number>;
+  ancestors: number[];
+
+  // For bidirectional linking, cycles are only allowed if all links on that cycle are same-table cursor-link
+  // this.ancestors only records what the ancestors are, but we need to record info about the edges between them.
+  // isAncCursLink[i]==true  means the link from ancestors[i] to ancestors[i+1] is a same-table cursor-link
+  // NOTE: (Since ancestors is a list of nodes, and this is a list of the edges between those nodes, this list will
+  //        be 1 shorter than ancestors (if there's no cycle), or will be the same length (if there is a cycle))
+  isAncestorSameTableCursorLink: boolean[];
 
   // the section record. Must be the empty record sections that are to be created.
   section: ViewSectionRec;
@@ -141,11 +148,53 @@ function isValidLink(source: LinkNode, target: LinkNode) {
     }
   }
 
-  // The link must not create a cycle
+  // The link must not create a cycle, unless it's only same-table cursor-links all the way to target
-  if (source.ancestors.has(target.section.getRowId())) {
+  if (source.ancestors.includes(target.section.getRowId())) {
+
+    // cycles only allowed for cursor links
+    if (source.column || target.column || source.isSummary) {
       return false;
     }
 
+    // We know our ancestors cycle back around to ourselves
+    // - lets walk back along the cyclic portion of the ancestor chain and verify that each link in that chain is
+    //   a cursor-link
+
+    // e.g. if the current link graph is:
+    //                     A->B->TGT->C->D->SRC
+    //    (SRC.ancestors):[5][4] [3] [2][1] [0]
+    // We're verifying the new potential link SRC->TGT, which would turn the graph into:
+    //             [from SRC] -> TGT -> C -> D -> SRC -> [to TGT]
+    // (Note that A and B will be cut away, since we change TGT's link source)
+    //
+    // We need to make sure that each link going backwards from `TGT -> C -> D -> SRC` is a same-table-cursor-link,
+    // since we disallow cycles with other kinds of links.
+    // isAncestorCursorLink[i] will tell us if the link going into ancestors[i] is a same-table-cursor-link
+    // So before we step from i=0 (SRC) to i=1 (D), we check isAncestorCursorLink[0], which tells us about D->SRC
+    let i;
+    for (i = 0; i < source.ancestors.length; i++) { // Walk backwards through the ancestors
+
+      // Once we hit the target section, we've seen all links that will be part of the cycle, and they've all been valid
+      if (source.ancestors[i] == target.section.getRowId()) {
+        break; // Success!
+      }
+
+      // Check that the link to the preceding section is valid
+      // NOTE! isAncestorSameTableCursorLink could be 1 shorter than ancestors!
+      // (e.g. if the graph looks like A->B->C, there's 3 ancestors but only two links)
+      // (however, if there's already a cycle, they'll be the same length ( [from C]->A->B->C, 3 ancestors & 3 links)
+      // If the link doesn't exist (shouldn't happen?) OR the link is not same-table-cursor, the cycle is invalid
+      if (i >= source.isAncestorSameTableCursorLink.length ||
+          !source.isAncestorSameTableCursorLink[i]) { return false; }
+    }
+
+    // If we've hit the last ancestor and haven't found target, error out (shouldn't happen!, we checked for it)
+    if (i == source.ancestors.length) { throw Error("Array doesn't include targetSection"); }
+
+
+    // Yay, this is a valid cycle of same-table cursor-links
+  }
+
   return true;
 }
 
@@ -224,15 +273,30 @@ function fromViewSectionRec(section: ViewSectionRec): LinkNode[] {
     return [];
   }
   const table = section.table.peek();
-  const ancestors = new Set<number>();
+  const ancestors: number[] = [];
+
+  const isAncestorSameTableCursorLink: boolean[] = [];
 
   for (let sec = section; sec.getRowId(); sec = sec.linkSrcSection.peek()) {
-    if (ancestors.has(sec.getRowId())) {
+    if (ancestors.includes(sec.getRowId())) {
-      // tslint:disable-next-line:no-console
+      // There's a cycle in the existing link graph
-      console.warn(`Links should not create a cycle - section ids: ${Array.from(ancestors)}`);
+      // TODO if we're feeling fancy, can test here whether it's an all-same-table cycle and warn if not
+      //      but there's other places we check for that
       break;
     }
-    ancestors.add(sec.getRowId());
+    ancestors.push(sec.getRowId());
+
+    //Determine if this link is a same-table cursor link
+    if (sec.linkSrcSection.peek().getRowId()) { // if sec has incoming link
+      const srcCol = sec.linkSrcCol.peek().getRowId();
+      const tgtCol = sec.linkTargetCol.peek().getRowId();
+      const srcTable = sec.linkSrcSection.peek().table.peek();
+      const srcIsSummary = srcTable.primaryTableId.peek() !== srcTable.tableId.peek();
+      isAncestorSameTableCursorLink.push(srcCol === 0 && tgtCol === 0 && !srcIsSummary);
+    }
+    // NOTE: isAncestorSameTableCursorLink may be 1 shorter than ancestors, since we might skip pushing
+    // when we hit the last ancestor (which has no incoming link)
+    // however if we have a cycle (of cursor-links), then they'll be the same length, because we won't skip last push
   }
 
   const isSummary = table.primaryTableId.peek() !== table.tableId.peek();
@@ -243,6 +307,7 @@ function fromViewSectionRec(section: ViewSectionRec): LinkNode[] {
     groupbyColumns: isSummary ? table.summarySourceColRefs.peek() : undefined,
     widgetType: section.parentKey.peek(),
     ancestors,
+    isAncestorSameTableCursorLink,
     section,
   };
 
@@ -280,7 +345,8 @@ function fromPageWidget(docModel: DocModel, pageWidget: IPageWidget): LinkNode[]
     // (e.g.: link from summary table with Attachments in group-by) but it seems to work fine as is
     groupbyColumns,
     widgetType: pageWidget.type,
-    ancestors: new Set(),
+    ancestors: [],
+    isAncestorSameTableCursorLink: [],
     section: docModel.viewSections.getRowModel(pageWidget.section),
   };
 

static/locales/en.client.json

@@ -90,7 +90,8 @@
         "Action Log failed to load": "Action Log failed to load",
         "Column {{colId}} was subsequently removed in action #{{action.actionNum}}": "Column {{colId}} was subsequently removed in action #{{action.actionNum}}",
         "Table {{tableId}} was subsequently removed in action #{{actionNum}}": "Table {{tableId}} was subsequently removed in action #{{actionNum}}",
-        "This row was subsequently removed in action {{action.actionNum}}": "This row was subsequently removed in action {{action.actionNum}}"
+        "This row was subsequently removed in action {{action.actionNum}}": "This row was subsequently removed in action {{action.actionNum}}",
+        "All tables": "All tables"
     },
     "AddNewButton": {
         "Add New": "Add New"
@@ -1019,7 +1020,12 @@
         "Anchor Links": "Anchor Links",
         "Custom Widgets": "Custom Widgets",
         "To make an anchor link that takes the user to a specific cell, click on a row and press {{shortcut}}.": "To make an anchor link that takes the user to a specific cell, click on a row and press {{shortcut}}.",
-        "You can choose one of our pre-made widgets or embed your own by providing its full URL.": "You can choose one of our pre-made widgets or embed your own by providing its full URL."
+        "You can choose one of our pre-made widgets or embed your own by providing its full URL.": "You can choose one of our pre-made widgets or embed your own by providing its full URL.",
+        "Calendar": "Calendar",
+        "Can't find the right columns? Click 'Change Widget' to select the table with events data.": "Can't find the right columns? Click 'Change Widget' to select the table with events data.",
+        "To configure your calendar, select columns for start": {
+            "end dates and event titles. Note each column's type.": "To configure your calendar, select columns for start/end dates and event titles. Note each column's type."
+        }
     },
     "DescriptionConfig": {
         "DESCRIPTION": "DESCRIPTION"

static/locales/sl.client.json

@@ -495,7 +495,8 @@
         "There are some things you should know when working with me:": "Pri sodelovanju z mano morate vedeti nekaj stvari:",
         "See our {{helpFunction}} and {{formulaCheat}}, or visit our {{community}} for more help.": "Oglejte si {{helpFunction}} in {{formulaCheat}}, za več pomoči pa obiščite {{community}}.",
         "Grist's AI Assistance": "Pomoč umetne inteligence",
-        "Grist's AI Formula Assistance. ": "Pomoč umetne inteligence pri formuli . "
+        "Grist's AI Formula Assistance. ": "Pomoč umetne inteligence pri formuli . ",
+        "Clear Conversation": "Briši pogovor"
     },
     "RightPanel": {
         "WIDGET TITLE": "NASLOV PRIPOMOČKA",
@@ -720,7 +721,8 @@
         "Close": "Zapri",
         "Opt in to Telemetry": "Prijava na telemetrijo",
         "Help Center": "Center za pomoč",
-        "Contribute": "Prispevajte"
+        "Contribute": "Prispevajte",
+        "Support Grist page": "Grist podpora"
     },
     "HomeIntro": {
         "personal site": "osebna stran",
@@ -934,5 +936,29 @@
         "Preview": "Predogled",
         "Apply": "Uporabi",
         "Cancel": "Prekliči"
+    },
+    "menus": {
+        "Integer": "Celo število",
+        "Text": "Tekst",
+        "Attachment": "Priponka",
+        "Choice": "Izbira",
+        "Select fields": "Izberi polja",
+        "Reference": "Referenca",
+        "Numeric": "Numeričen",
+        "Date": "Datum"
+    },
+    "errorPages": {
+        "Something went wrong": "Nekaj je šlo narobe",
+        "Sign in": "Vpiši se",
+        "Add account": "Dodaj račun",
+        "Signed out{{suffix}}": "Ponovno se vpiši",
+        "Sign in again": "Ponovno se vpiši"
+    },
+    "WidgetTitle": {
+        "DATA TABLE NAME": "IME PODATKOVNE TABELE",
+        "Save": "Shrani"
+    },
+    "breadcrumbs": {
+        "snapshot": "posnetek"
     }
 }

test/nbrowser/RightPanelSelectBy.ts

@@ -63,9 +63,23 @@ describe('RightPanelSelectBy', function() {
   });
 
 
-  it('should disallow creating cycles', async function() {
+  it('should disallow creating cycles if not cursor-linked', async function() {
+
+    //Link "films record" by "performances record"
+    await gu.openSelectByForSection('FILMS RECORD');
+    await driver.findContent('.test-select-row', /Performances record.*Film/i).click();
+    await gu.waitForServer();
+
+    // this link should no longer be present, since it would create a cycle with a filter link in it
     await gu.openSelectByForSection('PERFORMANCES RECORD');
-    assert.equal(await driver.findContent('.test-select-row', /Performances detail/).isPresent(), false);
+    assert.equal(await driver.findContent('.test-select-row', /Performances record.*Film/i).isPresent(), false);
+  });
+
+  it('should allow creating cursor-linked-cycles', async function() {
+    assert.equal(await driver.findContent('.test-select-row', /Performances detail/).isPresent(), true);
+
+    // undo, the operation from the previous test; link is expected to be unset for next test
+    await gu.undo();
   });