fix: per metrics view filter params override the legacy singular f param

web-common/src/features/dashboards/filters/ExpressionFilterManager.spec.ts

@@ -367,6 +367,36 @@ describe("setUrlParams", () => {
     ]);
   });
 
+  it("lets the per metrics view params override the singular one", () => {
+    const filterManager = createFilterManager();
+
+    // An embed host passes the legacy singular param, and the dashboard has since written its own
+    // per metrics view params. The latter are the newer state, so the singular param must not be
+    // ANDed in as a second condition on the same dimension: the chips cannot show that, and the
+    // two value sets together match nothing.
+    const searchParams = sharedParam(
+      `${AD_BIDS_PUBLISHER_DIMENSION} IN ('Google')`,
+    );
+    const ownParams = perMetricsViewParams({
+      [AD_BIDS_METRICS_NAME]: `${AD_BIDS_PUBLISHER_DIMENSION} IN ('Facebook')`,
+      [AD_BIDS_MIRROR_METRICS_NAME]: `${AD_BIDS_PUBLISHER_DIMENSION} IN ('Facebook')`,
+    });
+    ownParams.forEach((value, key) => searchParams.set(key, value));
+    filterManager.storeSync.setUrlParams(searchParams);
+
+    expect(filterManager.isComplexFilter).toBe(false);
+    expect(names(filterManager.sortedFilterManagers.dimensions)).toEqual([
+      AD_BIDS_PUBLISHER_DIMENSION,
+    ]);
+    expect(
+      filterManager.sortedFilterManagers.dimensions[0].selectedValues,
+    ).toEqual(["Facebook"]);
+    expect(filterManager.topLevelJoiner.param).toEqual({
+      [AD_BIDS_METRICS_NAME]: `${AD_BIDS_PUBLISHER_DIMENSION} IN ('Facebook')`,
+      [AD_BIDS_MIRROR_METRICS_NAME]: `${AD_BIDS_PUBLISHER_DIMENSION} IN ('Facebook')`,
+    });
+  });
+
   it("drops filters on identifiers the metrics view does not define", () => {
     const filterManager = createFilterManager();
 

web-common/src/features/dashboards/filters/ExpressionFilterManager.svelte.ts

@@ -164,17 +164,23 @@ export class ExpressionFilterManager implements UrlParamsStore {
     this.unsubscribers.forEach((unsub) => unsub());
   }
 
+  /**
+   * Folds the legacy singular `f` param into a param per metrics view.
+   *
+   * A metrics view that already has a param of its own keeps it, since that is the newer state:
+   * an embed host passes the singular param, and the dashboard then writes per metrics view params
+   * as the filter is edited. Merging the two instead would AND the host's condition with the edited
+   * one on the same dimension, which no chip can show and which usually matches nothing.
+   */
   public normalizeParams(urlParams: URLSearchParams): URLSearchParams {
     const singularParam = urlParams.get(ExploreStateURLParams.Filters);
     if (!singularParam || this.singleParamFormMv) return urlParams;
 
     const newUrlParams = new URLSearchParams();
-    this.metricsViewsProvider.metricsViewNames.forEach((mvName) =>
-      newUrlParams.set(
-        getParamKeyForMv(mvName, this.singleParamFormMv),
-        singularParam,
-      ),
-    );
+    this.metricsViewsProvider.metricsViewNames.forEach((mvName) => {
+      const paramKey = getParamKeyForMv(mvName, this.singleParamFormMv);
+      newUrlParams.set(paramKey, urlParams.get(paramKey) ?? singularParam);
+    });
     return newUrlParams;
   }
 

web-common/src/lib/store-utils/url-params-store-sync.svelte.ts

@@ -83,7 +83,7 @@ export class UrlParamsChangeTracker {
     if (this.searchParams?.toString() === relevantParams.toString()) return;
 
     this.searchParams = this.store.normalizeParams(relevantParams);
-    this.store.setUrlParams(relevantParams);
+    this.store.setUrlParams(this.searchParams);
     this.events.emit("change", this.searchParams);
   }