From e3b78bbf2eeb26f065848e930ca27f57d1ca4837 Mon Sep 17 00:00:00 2001
From: "Thomas J. Fan" <thomasjpfan@gmail.com>
Date: Tue, 12 Oct 2021 15:16:31 -0400
Subject: [PATCH 1/6] ENH Adds nicer message when notebook is not trusted

---
 sklearn/utils/_estimator_html_repr.py           | 14 ++++++++++++--
 sklearn/utils/tests/test_estimator_html_repr.py | 12 ++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/sklearn/utils/_estimator_html_repr.py b/sklearn/utils/_estimator_html_repr.py
index b2d38b9e97ab3..c01bb3eea9a88 100644
--- a/sklearn/utils/_estimator_html_repr.py
+++ b/sklearn/utils/_estimator_html_repr.py
@@ -309,6 +309,9 @@ def _write_estimator_html(
   display: inline-block;
   position: relative;
 }
+#$id div.sk-text-repr-fallback {
+  display: none;
+}
 """.replace(
     "  ", ""
 ).replace(
@@ -335,16 +338,23 @@ def estimator_html_repr(estimator):
         container_id = "sk-" + str(uuid.uuid4())
         style_template = Template(_STYLE)
         style_with_id = style_template.substitute(id=container_id)
+
+        estimator_str = str(estimator)
+        rerun_msg = (
+            "Please rerun this cell to show the HTML repr or trust the notebook."
+        )
+        fallback_html = f"<pre>{html.escape(estimator_str)}</pre><b>{rerun_msg}</b>"
         out.write(
             f"<style>{style_with_id}</style>"
             f'<div id="{container_id}" class"sk-top-container">'
-            '<div class="sk-container">'
+            f'<div class="sk-text-repr-fallback">{fallback_html}</div>'
+            '<div class="sk-container" hidden>'
         )
         _write_estimator_html(
             out,
             estimator,
             estimator.__class__.__name__,
-            str(estimator),
+            estimator_str,
             first_call=True,
         )
         out.write("</div></div>")
diff --git a/sklearn/utils/tests/test_estimator_html_repr.py b/sklearn/utils/tests/test_estimator_html_repr.py
index f22c03f20bdd7..9d474ad10fe10 100644
--- a/sklearn/utils/tests/test_estimator_html_repr.py
+++ b/sklearn/utils/tests/test_estimator_html_repr.py
@@ -1,4 +1,5 @@
 from contextlib import closing
+import html
 from io import StringIO
 
 import pytest
@@ -278,3 +279,14 @@ def test_one_estimator_print_change_only(print_changed_only):
         pca_repr = str(pca)
         html_output = estimator_html_repr(pca)
         assert pca_repr in html_output
+
+
+def test_fallback_exists():
+    """Check that repr fallback is in the HTML."""
+    pca = PCA(n_components=10)
+    html_output = estimator_html_repr(pca)
+
+    assert (
+        f'<div class="sk-text-repr-fallback"><pre>{html.escape(str(pca))}'
+        in html_output
+    )

From 6fa3fb3cdb37871ec6412ffe12de0992a4139714 Mon Sep 17 00:00:00 2001
From: "Thomas J. Fan" <thomasjpfan@gmail.com>
Date: Tue, 12 Oct 2021 15:48:20 -0400
Subject: [PATCH 2/6] DOC Adds whats new

---
 doc/whats_new/v1.1.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/doc/whats_new/v1.1.rst b/doc/whats_new/v1.1.rst
index 1a9f773ce08df..4a9f511ab9c1b 100644
--- a/doc/whats_new/v1.1.rst
+++ b/doc/whats_new/v1.1.rst
@@ -98,6 +98,10 @@ Changelog
   :pr:`20880` by :user:`Guillaume Lemaitre <glemaitre>`
   and :user:`András Simon <simonandras>`.
 
+- |Enhancement| :func:`utils.estimator_html_repr` shows a more helpful error
+  message when running in a jupyter notebook that is not trusted. :pr:`xxxxx`
+  by `Thomas Fan`_.
+
 Code and Documentation Contributors
 -----------------------------------
 

From 418836f14d969baf9a61c9a95c1dc99b8c9efbb0 Mon Sep 17 00:00:00 2001
From: "Thomas J. Fan" <thomasjpfan@gmail.com>
Date: Tue, 12 Oct 2021 16:01:04 -0400
Subject: [PATCH 3/6] DOC Adds PR number

---
 doc/whats_new/v1.1.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/whats_new/v1.1.rst b/doc/whats_new/v1.1.rst
index 4a9f511ab9c1b..2575c53fb705d 100644
--- a/doc/whats_new/v1.1.rst
+++ b/doc/whats_new/v1.1.rst
@@ -99,7 +99,7 @@ Changelog
   and :user:`András Simon <simonandras>`.
 
 - |Enhancement| :func:`utils.estimator_html_repr` shows a more helpful error
-  message when running in a jupyter notebook that is not trusted. :pr:`xxxxx`
+  message when running in a jupyter notebook that is not trusted. :pr:`21316`
   by `Thomas Fan`_.
 
 Code and Documentation Contributors

From 32f3103f7fdf3c9263553dbe34383643e3f534e0 Mon Sep 17 00:00:00 2001
From: "Thomas J. Fan" <thomasjpfan@gmail.com>
Date: Mon, 18 Oct 2021 09:55:26 -0400
Subject: [PATCH 4/6] DOC Adds comment on how fallback works

---
 sklearn/utils/_estimator_html_repr.py | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/sklearn/utils/_estimator_html_repr.py b/sklearn/utils/_estimator_html_repr.py
index c01bb3eea9a88..49391d0183918 100644
--- a/sklearn/utils/_estimator_html_repr.py
+++ b/sklearn/utils/_estimator_html_repr.py
@@ -338,16 +338,21 @@ def estimator_html_repr(estimator):
         container_id = "sk-" + str(uuid.uuid4())
         style_template = Template(_STYLE)
         style_with_id = style_template.substitute(id=container_id)
-
         estimator_str = str(estimator)
-        rerun_msg = (
+
+        # When the notebook is trusted, the CSS is loaded and
+        # div.sk-text-repr-fallback is set to display: none, hiding the fallback message
+        # If the notebook is not trusted, the CSS is not loaded, then fallback message
+        # is shown by default.
+        fallback_msg = (
             "Please rerun this cell to show the HTML repr or trust the notebook."
         )
-        fallback_html = f"<pre>{html.escape(estimator_str)}</pre><b>{rerun_msg}</b>"
         out.write(
             f"<style>{style_with_id}</style>"
             f'<div id="{container_id}" class"sk-top-container">'
-            f'<div class="sk-text-repr-fallback">{fallback_html}</div>'
+            '<div class="sk-text-repr-fallback">'
+            f"<pre>{html.escape(estimator_str)}</pre><b>{fallback_msg}</b>"
+            "</div>"
             '<div class="sk-container" hidden>'
         )
         _write_estimator_html(

From 76bf7979a9e7b4f3dd07f448fec15d23b77332fa Mon Sep 17 00:00:00 2001
From: "Thomas J. Fan" <thomasjpfan@gmail.com>
Date: Mon, 18 Oct 2021 09:56:26 -0400
Subject: [PATCH 5/6] DOC clearer

---
 sklearn/utils/_estimator_html_repr.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sklearn/utils/_estimator_html_repr.py b/sklearn/utils/_estimator_html_repr.py
index 49391d0183918..352f493f5bf8d 100644
--- a/sklearn/utils/_estimator_html_repr.py
+++ b/sklearn/utils/_estimator_html_repr.py
@@ -340,10 +340,10 @@ def estimator_html_repr(estimator):
         style_with_id = style_template.substitute(id=container_id)
         estimator_str = str(estimator)
 
-        # When the notebook is trusted, the CSS is loaded and
-        # div.sk-text-repr-fallback is set to display: none, hiding the fallback message
-        # If the notebook is not trusted, the CSS is not loaded, then fallback message
-        # is shown by default.
+        # When the notebook is trusted, the CSS is loaded which sets
+        # div.sk-text-repr-fallback to display: none, hiding the fallback message.
+        # If the notebook is not trusted, then the CSS is not loaded and
+        # the fallback message is shown by default.
         fallback_msg = (
             "Please rerun this cell to show the HTML repr or trust the notebook."
         )

From 66ce53902fbb782ecf66ce191879c918d5bb49cc Mon Sep 17 00:00:00 2001
From: "Thomas J. Fan" <thomasjpfan@gmail.com>
Date: Mon, 18 Oct 2021 10:02:34 -0400
Subject: [PATCH 6/6] CLN Improves comment

---
 sklearn/utils/_estimator_html_repr.py | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/sklearn/utils/_estimator_html_repr.py b/sklearn/utils/_estimator_html_repr.py
index 352f493f5bf8d..1f5c339c12771 100644
--- a/sklearn/utils/_estimator_html_repr.py
+++ b/sklearn/utils/_estimator_html_repr.py
@@ -340,10 +340,15 @@ def estimator_html_repr(estimator):
         style_with_id = style_template.substitute(id=container_id)
         estimator_str = str(estimator)
 
-        # When the notebook is trusted, the CSS is loaded which sets
-        # div.sk-text-repr-fallback to display: none, hiding the fallback message.
-        # If the notebook is not trusted, then the CSS is not loaded and
-        # the fallback message is shown by default.
+        # The fallback message is shown by default and loading the CSS sets
+        # div.sk-text-repr-fallback to display: none to hide the fallback message.
+        #
+        # If the notebook is trusted, the CSS is loaded which hides the fallback
+        # message. If the notebook is not trusted, then the CSS is not loaded and the
+        # fallback message is shown by default.
+        #
+        # The reverse logic applies to HTML repr div.sk-container.
+        # div.sk-container is hidden by default and the loading the CSS displays it.
         fallback_msg = (
             "Please rerun this cell to show the HTML repr or trust the notebook."
         )