health: expose DependsOn to local API via UnhealthyState (#12513)

Updates #4136

Small PR to expose the health Warnables dependencies to the GUI via LocalAPI, so that we can only show warnings for root cause issues, and filter out unnecessary messages before user presentation.

Signed-off-by: Andrea Gottardo <andrea@gottardo.me>

health/health_test.go

@@ -176,3 +176,38 @@ func TestRegisterWarnablePanicsWithDuplicate(t *testing.T) {
 	}()
 	Register(w)
 }
+
+// TestCheckDependsOnAppearsInUnhealthyState asserts that the DependsOn field in the UnhealthyState
+// is populated with the WarnableCode(s) of the Warnable(s) that a warning depends on.
+func TestCheckDependsOnAppearsInUnhealthyState(t *testing.T) {
+	ht := Tracker{}
+	w1 := Register(&Warnable{
+		Code:      "w1",
+		Text:      StaticMessage("W1 Text"),
+		DependsOn: []*Warnable{},
+	})
+	defer unregister(w1)
+	w2 := Register(&Warnable{
+		Code:      "w2",
+		Text:      StaticMessage("W2 Text"),
+		DependsOn: []*Warnable{w1},
+	})
+	defer unregister(w2)
+
+	ht.SetUnhealthy(w1, Args{ArgError: "w1 is unhealthy"})
+	us1, ok := ht.CurrentState().Warnings[w1.Code]
+	if !ok {
+		t.Fatalf("Expected an UnhealthyState for w1, got nothing")
+	}
+	if len(us1.DependsOn) != 0 {
+		t.Fatalf("Expected no DependsOn in the unhealthy state, got: %v", us1.DependsOn)
+	}
+	ht.SetUnhealthy(w2, Args{ArgError: "w2 is also unhealthy now"})
+	us2, ok := ht.CurrentState().Warnings[w2.Code]
+	if !ok {
+		t.Fatalf("Expected an UnhealthyState for w2, got nothing")
+	}
+	if !reflect.DeepEqual(us2.DependsOn, []WarnableCode{w1.Code}) {
+		t.Fatalf("Expected DependsOn = [w1.Code] in the unhealthy state, got: %v", us2.DependsOn)
+	}
+}