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#![doc = include_str!("../README.md")]
#![warn(
clippy::pedantic,
clippy::doc_markdown,
clippy::redundant_closure,
clippy::explicit_iter_loop,
clippy::match_same_arms,
clippy::needless_borrow,
clippy::print_stdout,
clippy::arithmetic_side_effects,
clippy::cast_possible_truncation,
clippy::unwrap_used,
clippy::map_unwrap_or,
clippy::trivially_copy_pass_by_ref,
clippy::needless_pass_by_value,
missing_docs,
missing_debug_implementations,
trivial_casts,
trivial_numeric_casts,
unreachable_pub,
unused_extern_crates,
unused_import_braces,
unused_qualifications,
variant_size_differences,
rust_2018_idioms,
rust_2018_compatibility,
rust_2021_compatibility
)]
#![allow(clippy::module_name_repetitions)]
pub mod error;
mod hasher;
mod html;
mod parser;
mod resolver;
pub use error::InlineError;
use indexmap::IndexMap;
#[cfg(feature = "stylesheet-cache")]
use lru::{DefaultHasher, LruCache};
use std::{borrow::Cow, fmt::Formatter, hash::BuildHasherDefault, io::Write, sync::Arc};
use crate::html::ElementStyleMap;
use hasher::BuildNoHashHasher;
use html::{Document, InliningMode};
pub use resolver::{DefaultStylesheetResolver, StylesheetResolver};
pub use url::{ParseError, Url};
/// An LRU Cache for external stylesheets.
#[cfg(feature = "stylesheet-cache")]
pub type StylesheetCache<S = DefaultHasher> = LruCache<String, String, S>;
/// Configuration options for CSS inlining process.
#[allow(clippy::struct_excessive_bools)]
pub struct InlineOptions<'a> {
/// Whether to inline CSS from "style" tags.
///
/// Sometimes HTML may include a lot of boilerplate styles, that are not applicable in every
/// scenario and it is useful to ignore them and use `extra_css` instead.
pub inline_style_tags: bool,
/// Keep "style" tags after inlining.
pub keep_style_tags: bool,
/// Keep "link" tags after inlining.
pub keep_link_tags: bool,
/// Used for loading external stylesheets via relative URLs.
pub base_url: Option<Url>,
/// Whether remote stylesheets should be loaded or not.
pub load_remote_stylesheets: bool,
/// External stylesheet cache.
#[cfg(feature = "stylesheet-cache")]
pub cache: Option<std::sync::Mutex<StylesheetCache>>,
// The point of using `Cow` here is Python bindings, where it is problematic to pass a reference
// without dealing with memory leaks & unsafe. With `Cow` we can use moved values as `String` in
// Python wrapper for `CSSInliner` and `&str` in Rust & simple functions on the Python side
/// Additional CSS to inline.
pub extra_css: Option<Cow<'a, str>>,
/// Pre-allocate capacity for HTML nodes during parsing.
/// It can improve performance when you have an estimate of the number of nodes in your HTML document.
pub preallocate_node_capacity: usize,
/// A way to resolve stylesheets from various sources.
pub resolver: Arc<dyn StylesheetResolver>,
}
impl<'a> std::fmt::Debug for InlineOptions<'a> {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
let mut debug = f.debug_struct("InlineOptions");
debug
.field("inline_style_tags", &self.inline_style_tags)
.field("keep_style_tags", &self.keep_style_tags)
.field("keep_link_tags", &self.keep_link_tags)
.field("base_url", &self.base_url)
.field("load_remote_stylesheets", &self.load_remote_stylesheets);
#[cfg(feature = "stylesheet-cache")]
{
debug.field("cache", &self.cache);
}
debug
.field("extra_css", &self.extra_css)
.field("preallocate_node_capacity", &self.preallocate_node_capacity)
.finish_non_exhaustive()
}
}
impl<'a> InlineOptions<'a> {
/// Override whether "style" tags should be inlined.
#[must_use]
pub fn inline_style_tags(mut self, inline_style_tags: bool) -> Self {
self.inline_style_tags = inline_style_tags;
self
}
/// Override whether "style" tags should be kept after processing.
#[must_use]
pub fn keep_style_tags(mut self, keep_style_tags: bool) -> Self {
self.keep_style_tags = keep_style_tags;
self
}
/// Override whether "link" tags should be kept after processing.
#[must_use]
pub fn keep_link_tags(mut self, keep_link_tags: bool) -> Self {
self.keep_link_tags = keep_link_tags;
self
}
/// Set base URL that will be used for loading external stylesheets via relative URLs.
#[must_use]
pub fn base_url(mut self, base_url: Option<Url>) -> Self {
self.base_url = base_url;
self
}
/// Override whether remote stylesheets should be loaded.
#[must_use]
pub fn load_remote_stylesheets(mut self, load_remote_stylesheets: bool) -> Self {
self.load_remote_stylesheets = load_remote_stylesheets;
self
}
/// Set external stylesheet cache.
#[must_use]
#[cfg(feature = "stylesheet-cache")]
pub fn cache(mut self, cache: impl Into<Option<StylesheetCache>>) -> Self {
if let Some(cache) = cache.into() {
self.cache = Some(std::sync::Mutex::new(cache));
} else {
self.cache = None;
}
self
}
/// Set additional CSS to inline.
#[must_use]
pub fn extra_css(mut self, extra_css: Option<Cow<'a, str>>) -> Self {
self.extra_css = extra_css;
self
}
/// Set the initial node capacity for HTML tree.
#[must_use]
pub fn preallocate_node_capacity(mut self, preallocate_node_capacity: usize) -> Self {
self.preallocate_node_capacity = preallocate_node_capacity;
self
}
/// Set the way to resolve stylesheets from various sources.
#[must_use]
pub fn resolver(mut self, resolver: Arc<dyn StylesheetResolver>) -> Self {
self.resolver = resolver;
self
}
/// Create a new `CSSInliner` instance from this options.
#[must_use]
pub const fn build(self) -> CSSInliner<'a> {
CSSInliner::new(self)
}
}
impl Default for InlineOptions<'_> {
#[inline]
fn default() -> Self {
InlineOptions {
inline_style_tags: true,
keep_style_tags: false,
keep_link_tags: false,
base_url: None,
load_remote_stylesheets: true,
#[cfg(feature = "stylesheet-cache")]
cache: None,
extra_css: None,
preallocate_node_capacity: 32,
resolver: Arc::new(DefaultStylesheetResolver),
}
}
}
/// A specialized `Result` type for CSS inlining operations.
pub type Result<T> = std::result::Result<T, InlineError>;
/// Customizable CSS inliner.
#[derive(Debug)]
pub struct CSSInliner<'a> {
options: InlineOptions<'a>,
}
const GROWTH_COEFFICIENT: f64 = 1.5;
// A rough coefficient to calculate the number of individual declarations based on the total CSS size.
const DECLARATION_SIZE_COEFFICIENT: f64 = 30.0;
fn allocate_output_buffer(html: &str) -> Vec<u8> {
// Allocating more memory than the input HTML, as the inlined version is usually bigger
#[allow(
clippy::cast_precision_loss,
clippy::cast_sign_loss,
clippy::cast_possible_truncation
)]
Vec::with_capacity(
(html.len() as f64 * GROWTH_COEFFICIENT)
.min(usize::MAX as f64)
.round() as usize,
)
}
impl<'a> CSSInliner<'a> {
/// Create a new `CSSInliner` instance with given options.
#[must_use]
#[inline]
pub const fn new(options: InlineOptions<'a>) -> Self {
CSSInliner { options }
}
/// Return a default `InlineOptions` that can fully configure the CSS inliner.
///
/// # Examples
///
/// Get default `InlineOptions`, then change base url
///
/// ```rust
/// use css_inline::{CSSInliner, Url};
/// # use url::ParseError;
/// # fn run() -> Result<(), ParseError> {
/// let url = Url::parse("https://api.example.com")?;
/// let inliner = CSSInliner::options()
/// .base_url(Some(url))
/// .build();
/// # Ok(())
/// # }
/// # run().unwrap();
/// ```
#[must_use]
#[inline]
pub fn options() -> InlineOptions<'a> {
InlineOptions::default()
}
/// Inline CSS styles from <style> tags to matching elements in the HTML tree and return a
/// string.
///
/// # Errors
///
/// Inlining might fail for the following reasons:
/// - Missing stylesheet file;
/// - Remote stylesheet is not available;
/// - IO errors;
/// - Internal CSS selector parsing error;
///
/// # Panics
///
/// This function may panic if external stylesheet cache lock is poisoned, i.e. another thread
/// using the same inliner panicked while resolving external stylesheets.
#[inline]
pub fn inline(&self, html: &str) -> Result<String> {
let mut out = allocate_output_buffer(html);
self.inline_to(html, &mut out)?;
Ok(String::from_utf8_lossy(&out).to_string())
}
/// Inline CSS & write the result to a generic writer. Use it if you want to write
/// the inlined document to a file.
///
/// # Errors
///
/// Inlining might fail for the following reasons:
/// - Missing stylesheet file;
/// - Remote stylesheet is not available;
/// - IO errors;
/// - Internal CSS selector parsing error;
///
/// # Panics
///
/// This function may panic if external stylesheet cache lock is poisoned, i.e. another thread
/// using the same inliner panicked while resolving external stylesheets.
#[inline]
pub fn inline_to<W: Write>(&self, html: &str, target: &mut W) -> Result<()> {
self.inline_to_impl(html, None, target, InliningMode::Document)
}
/// Inline CSS into an HTML fragment.
///
/// # Errors
///
/// Inlining might fail for the following reasons:
/// - Missing stylesheet file;
/// - Remote stylesheet is not available;
/// - IO errors;
/// - Internal CSS selector parsing error;
///
/// # Panics
///
/// This function may panic if external stylesheet cache lock is poisoned, i.e. another thread
/// using the same inliner panicked while resolving external stylesheets.
pub fn inline_fragment(&self, html: &str, css: &str) -> Result<String> {
let mut out = allocate_output_buffer(html);
self.inline_fragment_to(html, css, &mut out)?;
Ok(String::from_utf8_lossy(&out).to_string())
}
/// Inline CSS into an HTML fragment and write the result to a generic writer.
///
/// # Errors
///
/// Inlining might fail for the following reasons:
/// - Missing stylesheet file;
/// - Remote stylesheet is not available;
/// - IO errors;
/// - Internal CSS selector parsing error;
///
/// # Panics
///
/// This function may panic if external stylesheet cache lock is poisoned, i.e. another thread
/// using the same inliner panicked while resolving external stylesheets.
pub fn inline_fragment_to<W: Write>(
&self,
html: &str,
css: &str,
target: &mut W,
) -> Result<()> {
self.inline_to_impl(html, Some(css), target, InliningMode::Fragment)
}
#[allow(clippy::too_many_lines)]
fn inline_to_impl<W: Write>(
&self,
html: &str,
css: Option<&str>,
target: &mut W,
mode: InliningMode,
) -> Result<()> {
let document = Document::parse_with_options(
html.as_bytes(),
self.options.preallocate_node_capacity,
mode,
);
// CSS rules may overlap, and the final set of rules applied to an element depend on
// selectors' specificity - selectors with higher specificity have more priority.
// Inlining happens in two major steps:
// 1. All available styles are mapped to respective elements together with their
// selector's specificity. When two rules overlap on the same declaration, then
// the one with higher specificity replaces another.
// 2. Resulting styles are merged into existing "style" tags.
let mut size_estimate: usize = if self.options.inline_style_tags {
document
.styles()
.map(|s| {
// Add 1 to account for the extra `\n` char we add between styles
s.len().saturating_add(1)
})
.sum()
} else {
0
};
if let Some(extra_css) = &self.options.extra_css {
size_estimate = size_estimate.saturating_add(extra_css.len());
}
if let Some(css) = css {
size_estimate = size_estimate.saturating_add(css.len());
}
let mut raw_styles = String::with_capacity(size_estimate);
if self.options.inline_style_tags {
for style in document.styles() {
raw_styles.push_str(style);
raw_styles.push('\n');
}
}
if self.options.load_remote_stylesheets {
let mut links = document.stylesheets().collect::<Vec<&str>>();
links.sort_unstable();
links.dedup();
for href in &links {
let url = self.get_full_url(href);
#[cfg(feature = "stylesheet-cache")]
if let Some(lock) = self.options.cache.as_ref() {
let mut cache = lock.lock().expect("Cache lock is poisoned");
if let Some(cached) = cache.get(url.as_ref()) {
raw_styles.push_str(cached);
raw_styles.push('\n');
continue;
}
}
let css = self.options.resolver.retrieve(url.as_ref())?;
raw_styles.push_str(&css);
raw_styles.push('\n');
#[cfg(feature = "stylesheet-cache")]
if let Some(lock) = self.options.cache.as_ref() {
let mut cache = lock.lock().expect("Cache lock is poisoned");
cache.put(url.into_owned(), css);
}
}
}
if let Some(extra_css) = &self.options.extra_css {
raw_styles.push_str(extra_css);
}
if let Some(css) = css {
raw_styles.push_str(css);
}
let mut styles = IndexMap::with_capacity_and_hasher(128, BuildNoHashHasher::default());
let mut parse_input = cssparser::ParserInput::new(&raw_styles);
let mut parser = cssparser::Parser::new(&mut parse_input);
// Allocating some memory for all the parsed declarations
#[allow(
clippy::cast_precision_loss,
clippy::cast_sign_loss,
clippy::cast_possible_truncation
)]
let mut declarations = Vec::with_capacity(
((raw_styles.len() as f64 / DECLARATION_SIZE_COEFFICIENT)
.min(usize::MAX as f64)
.round() as usize)
.max(16),
);
let mut rule_list = Vec::with_capacity(declarations.capacity() / 3);
for rule in cssparser::StyleSheetParser::new(
&mut parser,
&mut parser::CSSRuleListParser::new(&mut declarations),
)
.flatten()
{
rule_list.push(rule);
}
let mut caches = document.build_caches();
for (selectors, (start, end)) in &rule_list {
// Only CSS Syntax Level 3 is supported, therefore it is OK to split by `,`
// With `is` or `where` selectors (Level 4) this split should be done on the parser level
for selector in selectors.split(',') {
if let Ok(matching_elements) = document.select(selector, &mut caches) {
let specificity = matching_elements.specificity();
for matching_element in matching_elements {
let element_styles =
styles.entry(matching_element.node_id).or_insert_with(|| {
ElementStyleMap::with_capacity_and_hasher(
end.saturating_sub(*start).saturating_add(4),
BuildHasherDefault::default(),
)
});
// Iterate over pairs of property name & value
// Example: `padding`, `0`
for (name, value) in &declarations[*start..*end] {
match element_styles.entry(name.as_ref()) {
indexmap::map::Entry::Occupied(mut entry) => {
if entry.get().0 <= specificity {
entry.insert((specificity, *value));
}
}
indexmap::map::Entry::Vacant(entry) => {
entry.insert((specificity, *value));
}
}
}
}
}
// Ignore not parsable selectors. E.g. there is no parser for @media queries
// Which means that they will fall into this category and will be ignored
}
}
document.serialize(
target,
styles,
self.options.keep_style_tags,
self.options.keep_link_tags,
mode,
)?;
Ok(())
}
fn get_full_url<'u>(&self, href: &'u str) -> Cow<'u, str> {
// Valid absolute URL
if Url::parse(href).is_ok() {
return Cow::Borrowed(href);
};
if let Some(base_url) = &self.options.base_url {
// Use the same scheme as the base URL
if href.starts_with("//") {
return Cow::Owned(format!("{}:{}", base_url.scheme(), href));
}
// Not a URL, then it is a relative URL
if let Ok(new_url) = base_url.join(href) {
return Cow::Owned(new_url.into());
}
};
// If it is not a valid URL and there is no base URL specified, we assume a local path
Cow::Borrowed(href)
}
}
impl Default for CSSInliner<'_> {
#[inline]
fn default() -> Self {
CSSInliner::new(InlineOptions::default())
}
}
/// Shortcut for inlining CSS with default parameters.
///
/// # Errors
///
/// Inlining might fail for the following reasons:
/// - Missing stylesheet file;
/// - Remote stylesheet is not available;
/// - IO errors;
/// - Internal CSS selector parsing error;
///
/// # Panics
///
/// This function may panic if external stylesheet cache lock is poisoned, i.e. another thread
/// using the same inliner panicked while resolving external stylesheets.
#[inline]
pub fn inline(html: &str) -> Result<String> {
CSSInliner::default().inline(html)
}
/// Shortcut for inlining CSS with default parameters and writing the output to a generic writer.
///
/// # Errors
///
/// Inlining might fail for the following reasons:
/// - Missing stylesheet file;
/// - Remote stylesheet is not available;
/// - IO errors;
/// - Internal CSS selector parsing error;
///
/// # Panics
///
/// This function may panic if external stylesheet cache lock is poisoned, i.e. another thread
/// using the same inliner panicked while resolving external stylesheets.
#[inline]
pub fn inline_to<W: Write>(html: &str, target: &mut W) -> Result<()> {
CSSInliner::default().inline_to(html, target)
}
/// Shortcut for inlining CSS into an HTML fragment with default parameters.
///
/// # Errors
///
/// Inlining might fail for the following reasons:
/// - Missing stylesheet file;
/// - Remote stylesheet is not available;
/// - IO errors;
/// - Internal CSS selector parsing error;
///
/// # Panics
///
/// This function may panic if external stylesheet cache lock is poisoned, i.e. another thread
/// using the same inliner panicked while resolving external stylesheets.
#[inline]
pub fn inline_fragment(html: &str, css: &str) -> Result<String> {
CSSInliner::default().inline_fragment(html, css)
}
/// Shortcut for inlining CSS into an HTML fragment with default parameters and writing the output to a generic writer.
///
/// # Errors
///
/// Inlining might fail for the following reasons:
/// - Missing stylesheet file;
/// - Remote stylesheet is not available;
/// - IO errors;
/// - Internal CSS selector parsing error;
///
/// # Panics
///
/// This function may panic if external stylesheet cache lock is poisoned, i.e. another thread
/// using the same inliner panicked while resolving external stylesheets.
#[inline]
pub fn inline_fragment_to<W: Write>(html: &str, css: &str, target: &mut W) -> Result<()> {
CSSInliner::default().inline_fragment_to(html, css, target)
}
#[cfg(test)]
mod tests {
use crate::{CSSInliner, InlineOptions};
#[test]
fn test_inliner_sync_send() {
fn assert_send<T: Send + Sync>() {}
assert_send::<CSSInliner<'_>>();
assert_send::<InlineOptions<'_>>();
}
}