addressing pr comments part 3

vizro-core/examples/default/app.py

@@ -525,10 +525,6 @@ def create_home_page():
         create_country_analysis(),
     ],
     navigation=vm.Navigation(
-        pages={
-            "Analysis": ["Homepage", "Variable Analysis"],
-            "Summary": ["Relationship Analysis", "Continent Summary", "Country Analysis"],
-        },
         selector=vm.NavBar(
             items=[
                 vm.NavItem(
@@ -541,7 +537,6 @@ def create_home_page():
                 ),
                 vm.NavItem(
                     pages=["Country Analysis"],
-                    text="Country Analysis is the set text for this icon",
                 ),
             ]
         ),

vizro-core/src/vizro/_constants.py

@@ -8,4 +8,3 @@
 FILTER_ACTION_PREFIX = "filter_action"
 PARAMETER_ACTION_PREFIX = "parameter_action"
 ACCORDION_DEFAULT_TITLE = "SELECT PAGE"
-MIN_NO_OF_PAGES = 2

vizro-core/src/vizro/models/__init__.py

@@ -29,9 +29,9 @@
     "Dropdown",
     "Filter",
     "Graph",
-    "NavItem",
     "Layout",
     "NavBar",
+    "NavItem",
     "Navigation",
     "Page",
     "Parameter",

vizro-core/src/vizro/models/_navigation/accordion.py

@@ -7,7 +7,7 @@
 from dash import html
 from pydantic import Field, validator
 
-from vizro._constants import ACCORDION_DEFAULT_TITLE, MIN_NO_OF_PAGES
+from vizro._constants import ACCORDION_DEFAULT_TITLE
 from vizro.models import VizroBaseModel
 from vizro.models._models_utils import _log_call
 from vizro.models._navigation._navigation_utils import _validate_pages

vizro-core/src/vizro/models/_navigation/nav_bar.py

@@ -4,8 +4,8 @@
 from typing import List, Optional
 
 from dash import html
+from pydantic import validator
 
-from vizro.managers import model_manager
 from vizro.models import VizroBaseModel
 from vizro.models._models_utils import _log_call
 from vizro.models._navigation.nav_item import NavItem
@@ -18,26 +18,21 @@ class NavBar(VizroBaseModel):
     Args:
         pages (Optional[NavPagesType]): See [`NavPagesType`][vizro.models.types.NavPagesType].
             Defaults to `None`.
-        items (List[NavItem]): List of NavItem models. Defaults to `[]`.
+        items (List[NavItem]): See [`NavItem`][vizro.models.NavItem]. Defaults to `[]`.
     """
 
     pages: Optional[NavPagesType] = None
     items: List[NavItem] = []
 
-    @_log_call
-    def pre_build(self):
-        from vizro.models._navigation import Navigation
-
-        _, navigation = next(model_manager._items_with_type(Navigation))
-
-        if self.pages is None:
-            self.pages = navigation.pages
+    @validator("items", always=True)
+    def validate_items(cls, items, values):
+        if not items:
+            if isinstance(values.get("pages"), list):
+                return [NavItem(pages=[page]) for page in values.get("pages")]
+            if isinstance(values.get("pages"), dict):
+                return [NavItem(pages=value) for page, value in values.get("pages").items()]
 
-        if not self.items:
-            if isinstance(self.pages, list):
-                self.items = [NavItem(pages=[page]) for page in self.pages]
-            if isinstance(self.pages, dict):
-                self.items = [NavItem(pages=value) for page, value in self.pages.items()]
+        return items
 
     @_log_call
     def build(self, active_page_id):

vizro-core/src/vizro/models/_navigation/nav_item.py

@@ -19,17 +19,20 @@ class NavItem(VizroBaseModel):
     """Icon to be used in Navigation Panel of Dashboard.
 
     Args:
-        tooltip (Optional[str]): Text to be displayed in the tooltip on icon hover.
-        icon (Optional[str]): URI (relative or absolute) of the embeddable content.
         pages (NavPagesType): See [NavPagesType][vizro.models.types.NavPagesType].
+        selector (Optional[Accordion]): See [`Accordion`][vizro.models.Accordion]. Defaults to `None`.
+        icon (Optional[str]): URI (relative or absolute) of the embeddable content.
+        max_text_length (int): Character limit for `text` argument. Defaults to 9.
+        text (str): Text to be display below the icon. Defaults to `""`.
+        tooltip (Optional[str]): Text to be displayed in the tooltip on icon hover.
     """
 
-    tooltip: Optional[str]
     icon: str = "home"
     pages: NavPagesType
     selector: Optional[Accordion] = None
-    text: Optional[str] = ""
     max_text_length: int = 9
+    text: str = ""
+    tooltip: Optional[str] = None
 
     # Re-used validators
     _validate_pages = validator("pages", allow_reuse=True, always=True)(_validate_pages)
@@ -47,28 +50,46 @@ def pre_build(self):
                 self.tooltip = self.text
                 self.text = self.text[:self.max_text_length]
 
+    @validator("text", always=True)
+    def set_text(cls, text, values):
+        if text and len(text) > values.get("max_text_length"):
+            return text[: values.get("max_text_length")]
+        return text
+
+    @validator("tooltip", always=True, pre=True)
+    def set_tooltip(cls, tooltip, values):
+        if tooltip is None:
+            if values.get("text") and len(values.get("text")) > values.get("max_text_length"):
+                return values.get("text")
+        return tooltip
+
     @_log_call
     def build(self, active_page_id):
+        icon_first_page = (
+            list(itertools.chain(*self.pages.values()))[0] if isinstance(self.pages, dict) else self.pages[0]
+        )
+        icon_div = (
+            html.Span(self.icon, className="material-symbols-outlined")
+            if self.icon
+            else html.Div(className="hidden")
+        )
+        text_div = html.Div(children=[self.text], className="icon-text") if self.text else html.Div(className="hidden")
+
         return dbc.Button(
             id=self.id,
             children=[
                 html.Div(
                     children=[
-                        html.Span(self.icon, className="material-symbols-outlined"),
-                        html.Div(
-                            children=[self.text],
-                            className="icon-text",
-                        )
-                        if self.text
-                        else html.Div(className="hidden"),
+                        icon_div,
+                        text_div,
                     ],
                     className="nav-icon-text",
                 ),
                 self._create_icon_tooltip(),
             ],
             className="icon-button",
-            href=dash.page_registry[self._get_first_page()]["relative_path"],
-            active=self._get_first_page() == active_page_id,
+            href=dash.page_registry[icon_first_page]["relative_path"],
+            active=icon_first_page == active_page_id,
         )
 
     def _create_icon_tooltip(self):
@@ -80,6 +101,3 @@ def _create_icon_tooltip(self):
                 className="custom-tooltip",
             )
             return tooltip
-
-    def _get_first_page(self):
-        return list(itertools.chain(*self.pages.values()))[0] if isinstance(self.pages, dict) else self.pages[0]

vizro-core/src/vizro/models/_navigation/navigation.py

@@ -33,6 +33,12 @@ class Navigation(VizroBaseModel):
     def set_selector(cls, selector, values):
         if selector is None:
             return Accordion(pages=values.get("pages"))
+
+        if isinstance(selector, NavBar):
+            if selector.pages is None and selector.items is None:
+                selector.pages = values.get("pages")
+                selector.items = []
+                return selector
         return selector
 
     @_log_call

vizro-core/src/vizro/models/types.py

@@ -319,3 +319,5 @@ class OptionsDictType(TypedDict):
     Union["Accordion", "NavBar"],
     Field(discriminator="type", description="Component that makes up part of the navigation panel"),
 ]
+"""Discriminated union. Permissible value types for selector attribute:
+[`Accordion`][vizro.models.Accordion], [`NavBar`][vizro.models.NavBar]."""