Use shared availability for an empty Street Level provider list

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+- Street Level with no providers uses the shared unavailable state and refuses
+  activation before initialization, while keeping its layer identity visible.
+
 - Application source configuration accepts replacements and explicit removal.
   Missing catalog feeds leave their layers unavailable without blocking startup
   or making fallback requests; malformed supplied feeds remain configuration errors.

docs/CURRENT-STATE.md

@@ -7,7 +7,8 @@ visibility lifecycle before initialization. Invalid supplied methods still fail
 construction. `createStandaloneApplication` and `createStandaloneCatalog` accept
 `sources` overrides; unspecified entries retain
 standalone defaults, and null entries explicitly remove a source. Street Level
-continues to accept an explicit provider list. Directions and Recent Imagery
+continues to accept an explicit provider list. An empty Street Level provider
+list uses the same unavailable lifecycle and disabled layer toggle. Directions and Recent Imagery
 acquisition are still selected by their application constructors.
 
 Application catalog composition accepts an optional `streetLevelProviders` list.

src/app/sourceComposition.test.mjs

@@ -82,3 +82,20 @@ test('standalone defaults allow exact replacements and explicit removal, and rej
     /Unknown source/,
   );
 });
+
+test('empty Street Level uses the shared unavailable lifecycle without initialization', async (t) => {
+  const actual = catalog({}, t);
+  const manager = new LayerLifecycle({});
+  manager.register(actual.get('street-level'));
+  assert.equal(await manager.setEnabled('street-level', true), false);
+  assert.equal(manager.layers.get('street-level').initialized, false);
+  const row = manager.getAll()[0];
+  assert.equal(row.stats.status, 'unavailable');
+  assert.equal(row.stats.error, 'No street-level imagery providers configured');
+  assert.equal(await manager.setEnabled('street-level', false), true);
+  const configured = catalog(createStandaloneLayerSources(), t);
+  assert.equal(
+    configured.get('street-level').getSourceAvailability().available,
+    true,
+  );
+});

src/layers/streetLevel/index.js

@@ -333,6 +333,16 @@ export function createStreetLevelLayer({
     requiresKeyId: requiresKeyIdFor(definitionsFrozen),
     /** Registered providers, in chip order. */
     providerIds: definitionsFrozen.map((def) => def.id),
+    getSourceAvailability() {
+      const available = definitionsFrozen.length > 0;
+      return {
+        available,
+        source: STREET_LEVEL_LAYER_ID,
+        reason: available
+          ? null
+          : 'No street-level imagery providers configured',
+      };
+    },
 
     init(viewer) {
       if (state.initialized)