feat: Make loading from an external URL be gated behind a feature. (#149)

* feat: Make loading from an external URL be gated behind a feature.

`attohttpc` and its transitive dependencies add a large amount of size
to the crate (on the order of about ~400 kB). For applications which
don't need external URL loading and are concerned with code size (for
example, a WASM binary), this is wasted space. Placing this stuff behind
a feature gate allows people to opt-out and reduce code size if they wish.

* fix: Add `http` feature by default for python and wasm bindings.

I'm assumining that these bindings expect `http` to be active. Having
`default_features` be false meant that these bindings weren't getting
the `http` gated code.

Author: a2aaron

bindings/python/Cargo.toml

@@ -17,6 +17,7 @@ built = { version = "0.5", features = ["chrono"] }
 path = "../../css-inline"
 version = "*"
 default-features = false
+features = ["http"]
 
 [dependencies]
 url = "2"

bindings/wasm/Cargo.toml

@@ -20,6 +20,7 @@ crate-type = ["cdylib"]
 path = "../../css-inline"
 version = "*"
 default-features = false
+features = ["http"]
 
 [dependencies]
 url = "2"

css-inline/Cargo.toml

@@ -15,14 +15,15 @@ categories = ["web-programming"]
 name = "css-inline"
 
 [features]
-default = ["cli"]
+default = ["cli", "http"]
 cli = ["pico-args", "rayon"]
+http = ["attohttpc"]
 
 [dependencies]
 cssparser = "0.29"
 kuchiki = "0.8"
 memchr = "2.4"
-attohttpc = { version = "0", default-features = false, features = ["compress", "tls-rustls"] }
+attohttpc = { version = "0", default-features = false, features = ["compress", "tls-rustls"], optional = true }
 url = "2"
 smallvec = "1"
 indexmap = "1.8.1"

css-inline/src/error.rs

@@ -19,6 +19,7 @@ pub enum InlineError {
     /// Input-output error. May happen during writing the resulting HTML.
     IO(io::Error),
     /// Network-related problem. E.g. resource is not available.
+    #[cfg(feature = "http")]
     Network(attohttpc::Error),
     /// Syntax errors or unsupported selectors.
     ParseError(Cow<'static, str>),
@@ -29,6 +30,8 @@ impl From<io::Error> for InlineError {
         Self::IO(error)
     }
 }
+
+#[cfg(feature = "http")]
 impl From<attohttpc::Error> for InlineError {
     fn from(error: attohttpc::Error) -> Self {
         Self::Network(error)
@@ -41,6 +44,7 @@ impl Display for InlineError {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self {
             Self::IO(error) => error.fmt(f),
+            #[cfg(feature = "http")]
             Self::Network(error) => error.fmt(f),
             Self::ParseError(error) => f.write_str(error),
             Self::MissingStyleSheet { path } => {

css-inline/src/lib.rs

@@ -24,7 +24,10 @@
     rust_2018_idioms,
     rust_2018_compatibility
 )]
+
+#[cfg(feature = "http")]
 use attohttpc::{Method, RequestBuilder};
+
 use kuchiki::{
     parse_html, traits::TendrilSink, ElementData, Node, NodeDataRef, NodeRef, Specificity,
 };
@@ -40,6 +43,7 @@ use std::{
     fs,
     io::{ErrorKind, Write},
 };
+
 pub use url::{ParseError, Url};
 
 /// Replace double quotes in property values.
@@ -267,6 +271,7 @@ impl<'a> CSSInliner<'a> {
                 style_tag.as_node().detach();
             }
         }
+
         if self.options.load_remote_stylesheets {
             let mut links = document
                 .select("link[rel~=stylesheet]")
@@ -338,9 +343,20 @@ impl<'a> CSSInliner<'a> {
 
 fn load_external(location: &str) -> Result<String> {
     if location.starts_with("https") | location.starts_with("http") {
-        let request = RequestBuilder::try_new(Method::GET, location)?;
-        let response = request.send()?;
-        Ok(response.text()?)
+        #[cfg(feature = "http")]
+        {
+            let request = RequestBuilder::try_new(Method::GET, location)?;
+            let response = request.send()?;
+            Ok(response.text()?)
+        }
+
+        #[cfg(not(feature = "http"))]
+        {
+            Err(InlineError::IO(std::io::Error::new(
+                ErrorKind::Unsupported,
+                "Loading external URLs requires the `http` feature",
+            )))
+        }
     } else {
         fs::read_to_string(location).map_err(|error| match error.kind() {
             ErrorKind::NotFound => InlineError::MissingStyleSheet {