Update custom-components import paths and tests (streamlit#8666)

## Describe your changes

Closes streamlit#8644

From [this
comment](streamlit#8644 (comment)):
The usage of `components.html` via `st.components.v1.html` was possible
prior to `1.34` due to [this
import](https://github.com/streamlit/streamlit/pull/8457/files#diff-3f73cf34a1595773b3b79ea85c5efd0c208e23beec4f812fa05419f87cff597eL32):
`from streamlit.components.v1.components import ComponentRegistry`,
which made it transiently available. This means that the usage via
`st.components.v1.html` is only possible when `server.py` is imported at
one point, which is not the case for example when running Streamlit as a
bare-script.

We have discussed this and thought about bringing the behavior back, but
this time explicitly and with tests 🙂
Final decision is still pending.

## Testing Plan

- E2E Tests
- Added new e2e test to test this import behavior. The tests are added
as extra files in order to start with a fresh context and not
accidentally have transient imports that make it appear as if it works.

---

**Contribution License Agreement**

By submitting this pull request you agree that all contributions to this
project are made under the Apache 2.0 license.

.github/workflows/playwright-changed-files.yml

@@ -30,7 +30,9 @@ jobs:
         uses: tj-actions/changed-files@v44
         with:
           path: e2e_playwright
-          files: "**/*_test.py"
+          files: |
+            "**/*_test.py"
+            "!**/custom_components/**/*" # ignore custom_components check in the fast-workflow as it requires additional dependencies
       - name: Check changed files
         id: check_changed_files
         env:

e2e_playwright/custom_components/popular_components.py

@@ -43,11 +43,27 @@
 
 
 def use_components_html():
+    # note that we import streamlit before and so this `components.html` working
+    # might be coincidental; this is the reason why we have dedicated tests for this kind of imports in the `st_components_v1_*` files
     import streamlit.components.v1 as components
 
     components.html("<div>Hello World!</div>")
 
 
+def use_components_iframe():
+    # note that we import streamlit before and so this `components.html` working
+    # might be coincidental; this is the reason why we have dedicated tests for this kind of imports in the `st_components_v1_*` files
+    import streamlit.components.v1 as components
+
+    st.write(str(components.iframe))
+
+
+def use_components_declare_component():
+    import streamlit.components.v1 as components
+
+    st.write(str(components.declare_component))
+
+
 # Different custom components:
 def use_streamlit_ace():
     from streamlit_ace import st_ace
@@ -179,6 +195,8 @@ def use_url_fragment():
 
 options: dict[str, Callable] = {
     "componentsHtml": use_components_html,
+    "componentsIframe": use_components_iframe,
+    "componentsDeclareComponent": use_components_declare_component,
     "ace": use_streamlit_ace,
     "aggrid": use_aggrid,
     "antd": use_antd,

e2e_playwright/custom_components/popular_components_test.py

@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import re
+
+import pytest
 from playwright.sync_api import Page, expect
 
 from e2e_playwright.conftest import wait_for_app_run
@@ -42,7 +45,28 @@ def test_components_html(app: Page):
     _expect_no_exception(app)
     _expect_iframe_attached(app)
     iframe = app.frame_locator("iframe")
-    expect(iframe.locator("div", has_text="Hello World!")).to_be_attached()
+    div = iframe.locator("div")
+    expect(div).to_have_text("Hello World!")
+
+
+@pytest.mark.parametrize(
+    ("name", "expected_text"),
+    [
+        ("componentsIframe", "bound method IframeMixin._iframe of DeltaGenerator()"),
+        ("componentsDeclareComponent", "function declare_component at"),
+    ],
+)
+def test_components_import(app: Page, name: str, expected_text: str):
+    """Test that components.iframe and components.declare_component can be imported and used.
+
+    We only make sure that they are importable but do not call them, so we don't have an iframe element in the DOM.
+    """
+    _select_component(app, name)
+    _expect_no_exception(app)
+    div = app.get_by_test_id("stMarkdownContainer").filter(
+        has_text=re.compile(f"<{expected_text}.*>")
+    )
+    expect(div).to_be_attached()
 
 
 def test_ace(app: Page):

e2e_playwright/shared/app_utils.py

@@ -145,7 +145,7 @@ def get_markdown(locator: Locator, text_inside_markdown: str | Pattern[str]) ->
 
 
 def expect_prefixed_markdown(
-    locator: Locator,
+    locator: Locator | Page,
     expected_prefix: str,
     expected_markdown: str | Pattern[str],
     exact_match: bool = False,
@@ -192,8 +192,29 @@ def expect_prefixed_markdown(
         expect(selection_text).to_contain_text(expected_markdown)
 
 
+def expect_markdown(
+    locator: Locator | Page,
+    expected_message: str | Pattern[str],
+) -> None:
+    """Expect an exception to be displayed in the app.
+
+    Parameters
+    ----------
+
+    locator : Locator
+        The locator to search for the exception element.
+
+    expected_markdown : str or Pattern[str]
+        The expected message to be displayed in the exception.
+    """
+    markdown_el = locator.get_by_test_id("stMarkdownContainer").filter(
+        has_text=expected_message
+    )
+    expect(markdown_el).to_be_visible()
+
+
 def expect_exception(
-    locator: Locator,
+    locator: Locator | Page,
     expected_message: str | Pattern[str],
 ) -> None:
     """Expect an exception to be displayed in the app.

e2e_playwright/st_components_v1_import_legacy_file.py

@@ -0,0 +1,23 @@
+# Copyright (c) Streamlit Inc. (2018-2022) Snowflake Inc. (2022-2024)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+# PLEASE DO NOT ADD MORE IMPORTS HERE OR MOVE THE CODE TO ANOTHER FILE.
+# This file relies on a clean import to make sure the functionality is not made available transiently.
+# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+from streamlit.components.v1 import components
+
+components.declare_component
+components.CustomComponent

e2e_playwright/st_components_v1_import_legacy_file_test.py

@@ -0,0 +1,19 @@
+# Copyright (c) Streamlit Inc. (2018-2022) Snowflake Inc. (2022-2024)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from playwright.sync_api import Page, expect
+
+
+def test_imports_dont_throw(app: Page):
+    expect(app.get_by_test_id("stException")).not_to_be_visible()

e2e_playwright/st_components_v1_import_via_st.py

@@ -0,0 +1,24 @@
+# Copyright (c) Streamlit Inc. (2018-2022) Snowflake Inc. (2022-2024)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+# PLEASE DO NOT ADD MORE IMPORTS HERE OR MOVE THE CODE TO ANOTHER FILE.
+# This file relies on a clean import to make sure the functionality is not made available transiently.
+# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+import streamlit as st
+
+st.components.v1.html("<div>This import and usage worked!</div>")
+st.write(str(st.components.v1.iframe))
+st.write(str(st.components.v1.declare_component))

e2e_playwright/st_components_v1_import_via_st_test.py

@@ -0,0 +1,29 @@
+# Copyright (c) Streamlit Inc. (2018-2022) Snowflake Inc. (2022-2024)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import re
+
+from playwright.sync_api import Page, expect
+
+from e2e_playwright.shared.app_utils import expect_markdown
+
+
+def test_components_v1_was_imported_successfully(app: Page):
+    expect(app.locator("iframe")).to_be_attached()
+    iframe = app.frame_locator("iframe")
+    div = iframe.locator("div")
+    expect(div).to_have_text("This import and usage worked!")
+
+    expect_markdown(app, "<bound method IframeMixin._iframe of DeltaGenerator()>")
+    expect_markdown(app, re.compile("<function declare_component at .*>"))

lib/streamlit/__init__.py

@@ -265,3 +265,8 @@ def _update_logger() -> None:
 experimental_connection = _deprecate_func_name(
     connection, "experimental_connection", "2024-04-01", name_override="connection"
 )
+
+# make it possible to call streamlit.components.v1.html etc. by importing it here
+# import in the very end to avoid partially-initialized module import errors, because
+# streamlit.components.v1 also uses some streamlit imports
+import streamlit.components.v1  # noqa: F401

lib/streamlit/components/v1/custom_component.py

@@ -17,8 +17,8 @@
 import json
 from typing import TYPE_CHECKING, Any
 
-from streamlit import _main, type_util
 from streamlit.components.types.base_custom_component import BaseCustomComponent
+from streamlit.delta_generator import main_dg
 from streamlit.elements.form import current_form_id
 from streamlit.elements.lib.policies import check_cache_replay_rules
 from streamlit.errors import StreamlitAPIException
@@ -29,7 +29,7 @@
 from streamlit.runtime.scriptrunner import get_script_run_ctx
 from streamlit.runtime.state import NoValue, register_widget
 from streamlit.runtime.state.common import compute_widget_id
-from streamlit.type_util import to_bytes
+from streamlit.type_util import is_bytes_like, is_dataframe_like, to_bytes
 
 if TYPE_CHECKING:
     from streamlit.delta_generator import DeltaGenerator
@@ -122,12 +122,12 @@ def create_instance(
         json_args = {}
         special_args = []
         for arg_name, arg_val in all_args.items():
-            if type_util.is_bytes_like(arg_val):
+            if is_bytes_like(arg_val):
                 bytes_arg = SpecialArg()
                 bytes_arg.key = arg_name
                 bytes_arg.bytes = to_bytes(arg_val)
                 special_args.append(bytes_arg)
-            elif type_util.is_dataframe_like(arg_val):
+            elif is_dataframe_like(arg_val):
                 dataframe_arg = SpecialArg()
                 dataframe_arg.key = arg_name
                 component_arrow.marshall(dataframe_arg.arrow_dataframe.data, arg_val)
@@ -221,7 +221,7 @@ def deserialize_component(ui_value, widget_id=""):
 
         # We currently only support writing to st._main, but this will change
         # when we settle on an improved API in a post-layout world.
-        dg = _main
+        dg = main_dg
 
         element = Element()
         return_value = marshall_component(dg, element)