Add single_config_entry manifest option (#109505)

* Allow setting if we support multiple config entries in config flow

* Move property to config flow instead of flow handler

* Move marking an integration as single instance only to manifest

* Revert line remove

* Avoid init a config flow or adding a new entry on a single instance with an entry

* Revert changes in test

* Process code review comments

* Apply code review suggestion

tests/test_config_entries.py

@@ -4434,6 +4434,177 @@ async def test_hashable_non_string_unique_id(
     assert entries.get_entry_by_domain_and_unique_id("test", unique_id) is None
 
 
+async def test_avoid_starting_config_flow_on_single_config_entry(
+    hass: HomeAssistant, manager: config_entries.ConfigEntries
+) -> None:
+    """Test that we cannot start a config flow for a single config entry integration."""
+    integration = loader.Integration(
+        hass,
+        "components.comp",
+        None,
+        {
+            "name": "Comp",
+            "dependencies": [],
+            "requirements": [],
+            "domain": "comp",
+            "single_config_entry": True,
+        },
+    )
+    entry = MockConfigEntry(
+        domain="comp",
+        unique_id="1234",
+        title="Test",
+        data={"vendor": "data"},
+        options={"vendor": "options"},
+    )
+    entry.add_to_hass(hass)
+
+    mock_platform(hass, "comp.config_flow", None)
+
+    with patch(
+        "homeassistant.loader.async_get_integration",
+        return_value=integration,
+    ), pytest.raises(
+        HomeAssistantError,
+        match=r"Cannot start a config flow, the integration supports only a single config entry but already has one",
+    ):
+        await hass.config_entries.flow.async_init("comp", context={"source": "user"})
+
+
+async def test_avoid_adding_second_config_entry_on_single_config_entry(
+    hass: HomeAssistant, manager: config_entries.ConfigEntries
+) -> None:
+    """Test that we cannot add a second entry for a single config entry integration."""
+    integration = loader.Integration(
+        hass,
+        "components.comp",
+        None,
+        {
+            "name": "Comp",
+            "dependencies": [],
+            "requirements": [],
+            "domain": "comp",
+            "single_config_entry": True,
+        },
+    )
+    entry = MockConfigEntry(
+        domain="comp",
+        unique_id="1234",
+        title="Test",
+        data={"vendor": "data"},
+        options={"vendor": "options"},
+    )
+    entry.add_to_hass(hass)
+
+    with patch(
+        "homeassistant.loader.async_get_integration",
+        return_value=integration,
+    ), pytest.raises(
+        HomeAssistantError,
+        match=r"An entry for comp already exists, but integration supports only one config entry",
+    ):
+        await hass.config_entries.async_add(
+            MockConfigEntry(
+                title="Second comp entry", domain="comp", data={"vendor": "data2"}
+            )
+        )
+
+
+async def test_in_progress_get_canceled_when_entry_is_created(
+    hass: HomeAssistant, manager: config_entries.ConfigEntries
+) -> None:
+    """Test that we abort all in progress flows when a new entry is created on a single instance only integration."""
+    integration = loader.Integration(
+        hass,
+        "components.comp",
+        None,
+        {
+            "name": "Comp",
+            "dependencies": [],
+            "requirements": [],
+            "domain": "comp",
+            "single_config_entry": True,
+        },
+    )
+    mock_integration(hass, MockModule("comp"))
+    mock_platform(hass, "comp.config_flow", None)
+
+    class TestFlow(config_entries.ConfigFlow):
+        """Test flow."""
+
+        VERSION = 1
+
+        async def async_step_user(self, user_input=None):
+            """Test user step."""
+            if user_input is not None:
+                return self.async_create_entry(title="Test Title", data=user_input)
+
+            return self.async_show_form(step_id="user")
+
+    with patch.dict(config_entries.HANDLERS, {"comp": TestFlow}), patch(
+        "homeassistant.loader.async_get_integration",
+        return_value=integration,
+    ):
+        # Create one to be in progress
+        result = await manager.flow.async_init(
+            "comp", context={"source": config_entries.SOURCE_USER}
+        )
+        assert result["type"] == data_entry_flow.FlowResultType.FORM
+
+        # Will be canceled
+        result2 = await manager.flow.async_init(
+            "comp", context={"source": config_entries.SOURCE_USER}
+        )
+        assert result2["type"] == data_entry_flow.FlowResultType.FORM
+
+        result = await manager.flow.async_configure(
+            result["flow_id"], user_input={"host": "127.0.0.1"}
+        )
+        assert result["type"] == data_entry_flow.FlowResultType.CREATE_ENTRY
+
+    assert len(manager.flow.async_progress()) == 0
+    assert len(manager.async_entries()) == 1
+
+
+async def test_start_reauth_still_possible_for_single_config_entry(
+    hass: HomeAssistant, manager: config_entries.ConfigEntries
+):
+    """Test that we can still start a reauth flow on a single config entry integration."""
+    integration = loader.Integration(
+        hass,
+        "components.comp",
+        None,
+        {
+            "name": "Comp",
+            "dependencies": [],
+            "requirements": [],
+            "domain": "comp",
+            "single_config_entry": True,
+        },
+    )
+    entry = MockConfigEntry(
+        domain="comp",
+        unique_id="1234",
+        title="Test",
+        data={"vendor": "data"},
+        options={"vendor": "options"},
+    )
+    entry.add_to_hass(hass)
+
+    mock_platform(hass, "comp.config_flow", None)
+
+    with patch(
+        "homeassistant.loader.async_get_integration",
+        return_value=integration,
+    ):
+        result = await hass.config_entries.flow.async_init(
+            "comp", context={"source": config_entries.SOURCE_REAUTH}
+        )
+
+    assert result["type"] == data_entry_flow.FlowResultType.FORM
+    assert result["step_id"] == "reauth_confirm"
+
+
 async def test_directly_mutating_blocked(
     hass: HomeAssistant, caplog: pytest.LogCaptureFixture
 ) -> None: