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Simplify HTML Formatter Style Handling Using Script Injection #1177

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Jul 4, 2025
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Simplify HTML Formatter Style Handling Using Script Injection #1177

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117 changes: 40 additions & 77 deletions python/datafusion/dataframe_formatter.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -135,9 +135,6 @@ class DataFrameHtmlFormatter:
session
"""

# Class variable to track if styles have been loaded in the notebook
_styles_loaded = False

def __init__(
self,
max_cell_length: int = 25,
Expand Down Expand Up @@ -260,23 +257,6 @@ def set_custom_header_builder(self, builder: Callable[[Any], str]) -> None:
"""
self._custom_header_builder = builder

@classmethod
def is_styles_loaded(cls) -> bool:
"""Check if HTML styles have been loaded in the current session.

This method is primarily intended for debugging UI rendering issues
related to style loading.

Returns:
True if styles have been loaded, False otherwise

Example:
>>> from datafusion.dataframe_formatter import DataFrameHtmlFormatter
>>> DataFrameHtmlFormatter.is_styles_loaded()
False
"""
return cls._styles_loaded

def format_html(
self,
batches: list,
Expand Down Expand Up @@ -315,18 +295,7 @@ def format_html(
# Build HTML components
html = []

# Only include styles and scripts if:
# 1. Not using shared styles, OR
# 2. Using shared styles but they haven't been loaded yet
include_styles = (
not self.use_shared_styles or not DataFrameHtmlFormatter._styles_loaded
)

if include_styles:
html.extend(self._build_html_header())
# If we're using shared styles, mark them as loaded
if self.use_shared_styles:
DataFrameHtmlFormatter._styles_loaded = True
html.extend(self._build_html_header())

html.extend(self._build_table_container_start())

Expand All @@ -338,7 +307,7 @@ def format_html(
html.append("</div>")

# Add footer (JavaScript and messages)
if include_styles and self.enable_cell_expansion:
if self.enable_cell_expansion:
html.append(self._get_javascript())

# Always add truncation message if needed (independent of styles)
Expand Down Expand Up @@ -375,14 +344,20 @@ def format_str(

def _build_html_header(self) -> list[str]:
"""Build the HTML header with CSS styles."""
html = []
html.append("<style>")
# Only include expandable CSS if cell expansion is enabled
if self.enable_cell_expansion:
html.append(self._get_default_css())
default_css = self._get_default_css() if self.enable_cell_expansion else ""
script = f"""
<script>
if (!document.getElementById('df-styles')) {{
const style = document.createElement('style');
style.id = 'df-styles';
style.textContent = `{default_css}`;
document.head.appendChild(style);
}}
</script>
"""
html = [script]
if self.custom_css:
html.append(self.custom_css)
html.append("</style>")
html.append(f"<style>{self.custom_css}</style>")
return html

def _build_table_container_start(self) -> list[str]:
Expand Down Expand Up @@ -570,28 +545,31 @@ def _get_default_css(self) -> str:
def _get_javascript(self) -> str:
"""Get JavaScript code for interactive elements."""
return """
<script>
function toggleDataFrameCellText(table_uuid, row, col) {
var shortText = document.getElementById(
table_uuid + "-min-text-" + row + "-" + col
);
var fullText = document.getElementById(
table_uuid + "-full-text-" + row + "-" + col
);
var button = event.target;

if (fullText.style.display === "none") {
shortText.style.display = "none";
fullText.style.display = "inline";
button.textContent = "(less)";
} else {
shortText.style.display = "inline";
fullText.style.display = "none";
button.textContent = "...";
}
}
</script>
"""
<script>
if (!window.__df_formatter_js_loaded__) {
window.__df_formatter_js_loaded__ = true;
window.toggleDataFrameCellText = function (table_uuid, row, col) {
var shortText = document.getElementById(
table_uuid + "-min-text-" + row + "-" + col
);
var fullText = document.getElementById(
table_uuid + "-full-text-" + row + "-" + col
);
var button = event.target;

if (fullText.style.display === "none") {
shortText.style.display = "none";
fullText.style.display = "inline";
button.textContent = "(less)";
} else {
shortText.style.display = "inline";
fullText.style.display = "none";
button.textContent = "...";
}
};
}
</script>
"""


class FormatterManager:
Expand Down Expand Up @@ -712,24 +690,9 @@ def reset_formatter() -> None:
>>> reset_formatter() # Reset formatter to default settings
"""
formatter = DataFrameHtmlFormatter()
# Reset the styles_loaded flag to ensure styles will be reloaded
DataFrameHtmlFormatter._styles_loaded = False
set_formatter(formatter)


def reset_styles_loaded_state() -> None:
"""Reset the styles loaded state to force reloading of styles.

This can be useful when switching between notebook sessions or
when styles need to be refreshed.

Example:
>>> from datafusion.html_formatter import reset_styles_loaded_state
>>> reset_styles_loaded_state() # Force styles to reload in next render
"""
DataFrameHtmlFormatter._styles_loaded = False


def _refresh_formatter_reference() -> None:
"""Refresh formatter reference in any modules using it.

Expand Down
60 changes: 23 additions & 37 deletions python/tests/test_dataframe.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,6 @@
configure_formatter,
get_formatter,
reset_formatter,
reset_styles_loaded_state,
)
from datafusion.expr import Window
from pyarrow.csv import write_csv
Expand Down Expand Up @@ -2177,27 +2176,15 @@ def test_html_formatter_shared_styles(df, clean_formatter_state):
# First, ensure we're using shared styles
configure_formatter(use_shared_styles=True)

# Get HTML output for first table - should include styles
html_first = df._repr_html_()

# Verify styles are included in first render
assert "<style>" in html_first
assert ".expandable-container" in html_first

# Get HTML output for second table - should NOT include styles
html_second = df._repr_html_()

# Verify styles are NOT included in second render
assert "<script>" in html_first
assert "df-styles" in html_first
assert "<script>" in html_second
assert "df-styles" in html_second
assert "<style>" not in html_first
assert "<style>" not in html_second
assert ".expandable-container" not in html_second

# Reset the styles loaded state and verify styles are included again
reset_styles_loaded_state()
html_after_reset = df._repr_html_()

# Verify styles are included after reset
assert "<style>" in html_after_reset
assert ".expandable-container" in html_after_reset


def test_html_formatter_no_shared_styles(df, clean_formatter_state):
Expand All @@ -2206,15 +2193,15 @@ def test_html_formatter_no_shared_styles(df, clean_formatter_state):
# Configure formatter to NOT use shared styles
configure_formatter(use_shared_styles=False)

# Generate HTML multiple times
html_first = df._repr_html_()
html_second = df._repr_html_()

# Verify styles are included in both renders
assert "<style>" in html_first
assert "<style>" in html_second
assert ".expandable-container" in html_first
assert ".expandable-container" in html_second
assert "<script>" in html_first
assert "<script>" in html_second
assert "df-styles" in html_first
assert "df-styles" in html_second
assert "<style>" not in html_first
assert "<style>" not in html_second


def test_html_formatter_manual_format_html(clean_formatter_state):
Expand All @@ -2228,20 +2215,15 @@ def test_html_formatter_manual_format_html(clean_formatter_state):

formatter = get_formatter()

# First call should include styles
html_first = formatter.format_html([batch], batch.schema)
assert "<style>" in html_first

# Second call should not include styles (using shared styles by default)
html_second = formatter.format_html([batch], batch.schema)
assert "<style>" not in html_second

# Reset loaded state
reset_styles_loaded_state()

# After reset, styles should be included again
html_reset = formatter.format_html([batch], batch.schema)
assert "<style>" in html_reset
assert "<script>" in html_first
assert "<script>" in html_second
assert "df-styles" in html_first
assert "df-styles" in html_second
assert "<style>" not in html_first
assert "<style>" not in html_second

# Create a new formatter with shared_styles=False
local_formatter = DataFrameHtmlFormatter(use_shared_styles=False)
Expand All @@ -2250,8 +2232,12 @@ def test_html_formatter_manual_format_html(clean_formatter_state):
local_html_1 = local_formatter.format_html([batch], batch.schema)
local_html_2 = local_formatter.format_html([batch], batch.schema)

assert "<style>" in local_html_1
assert "<style>" in local_html_2
assert "<script>" in local_html_1
assert "<script>" in local_html_2
assert "df-styles" in local_html_1
assert "df-styles" in local_html_2
assert "<style>" not in local_html_1
assert "<style>" not in local_html_2


def test_fill_null_basic(null_df):
Expand Down