feat(cli): --extra-css-file option to load additional CSS from files

Signed-off-by: Dmitry Dygalo <dmitry@dygalo.dev>

Author: Stranger6667

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- **CLI**: `--extra-css-file` option to load additional CSS from files. [#67](https://github.com/Stranger6667/css-inline/pull/67)
+
 ### Changed
 
 - **CLI**: Remove `pico-args`

css-inline/src/main.rs

@@ -55,6 +55,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         keep_link_tags: bool,
         base_url: Option<String>,
         extra_css: Option<String>,
+        extra_css_files: Vec<String>,
         output_filename_prefix: Option<OsString>,
         load_remote_stylesheets: bool,
         #[cfg(feature = "stylesheet-cache")]
@@ -72,6 +73,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                 keep_link_tags: false,
                 base_url: None,
                 extra_css: None,
+                extra_css_files: Vec::new(),
                 output_filename_prefix: None,
                 load_remote_stylesheets: false,
                 #[cfg(feature = "stylesheet-cache")]
@@ -101,6 +103,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             "inline-style-tags"
                 | "base-url"
                 | "extra-css"
+                | "extra-css-file"
                 | "output-filename-prefix"
                 | if_cfg_feature_stylesheet_cache!("cache-size")
         )
@@ -125,6 +128,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             "inline-style-tags" => parsed.inline_style_tags = parse_value(value, flag)?,
             "base-url" => parsed.base_url = Some(value.to_string()),
             "extra-css" => parsed.extra_css = Some(value.to_string()),
+            "extra-css-file" => parsed.extra_css_files.push(value.to_string()),
             "output-filename-prefix" => {
                 parsed.output_filename_prefix = Some(value.to_string().into());
             }
@@ -155,6 +159,32 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         Ok(())
     }
 
+    fn combine_extra_css(
+        extra_css: Option<String>,
+        extra_css_files: Vec<String>,
+    ) -> Result<Option<String>, Box<dyn std::error::Error>> {
+        let mut buffer = extra_css.unwrap_or_default();
+
+        if !buffer.is_empty() {
+            buffer.push('\n');
+        }
+
+        for path in extra_css_files {
+            let mut file =
+                File::open(&path).map_err(|e| format!("Failed to read CSS file '{path}': {e}"))?;
+            file.read_to_string(&mut buffer)?;
+            if !buffer.is_empty() {
+                buffer.push('\n');
+            }
+        }
+
+        Ok(if buffer.is_empty() {
+            None
+        } else {
+            Some(buffer)
+        })
+    }
+
     fn format_error(filename: Option<&str>, error: impl fmt::Display) {
         let mut buffer = String::with_capacity(128);
         if let Some(filename) = filename {
@@ -212,6 +242,10 @@ OPTIONS:
     --extra-css
         Additional CSS to inline.
 
+    --extra-css-file <PATH>
+        Load additional CSS from a file to inline. Can be used multiple times to load
+        from several files. The CSS will be processed alongside any existing styles.
+
     --output-filename-prefix
         Custom prefix for output files. Defaults to `inlined.`.
 "#
@@ -280,6 +314,13 @@ OPTIONS:
         } else {
             None
         };
+        let extra_css = match combine_extra_css(args.extra_css, args.extra_css_files) {
+            Ok(css) => css,
+            Err(error) => {
+                format_error(None, error);
+                std::process::exit(1);
+            }
+        };
         let options = InlineOptions {
             inline_style_tags: args.inline_style_tags,
             keep_style_tags: args.keep_style_tags,
@@ -288,7 +329,7 @@ OPTIONS:
             load_remote_stylesheets: args.load_remote_stylesheets,
             #[cfg(feature = "stylesheet-cache")]
             cache,
-            extra_css: args.extra_css.as_deref().map(Cow::Borrowed),
+            extra_css: extra_css.as_deref().map(Cow::Borrowed),
             preallocate_node_capacity: 32,
             resolver: Arc::new(DefaultStylesheetResolver),
         };

css-inline/tests/extra.css

@@ -0,0 +1,3 @@
+.test-class {
+  background: red;
+}

css-inline/tests/test_cli.rs

@@ -89,6 +89,55 @@ pub mod tests {
             .stderr("Status: ERROR\nDetails: empty host\n");
     }
 
+    #[test]
+    fn extra_css_file() {
+        css_inline()
+            .arg("tests/example.html")
+            .arg("--extra-css-file=tests/extra.css")
+            .arg("--output-filename-prefix=inlined.extra-css.")
+            .assert()
+            .success()
+            .stdout("tests/example.html: SUCCESS\n");
+
+        let content = fs::read_to_string("tests/inlined.extra-css.example.html").unwrap();
+        assert!(
+            content.contains(r#"style="color: #ffffff;background: red;""#),
+            "inlined output did not include extra-css rules:\n{}",
+            content
+        );
+    }
+
+    #[test]
+    fn extra_css_file_not_found() {
+        css_inline()
+            .arg("tests/example.html")
+            .arg("--extra-css-file=tests/nonexistent.css")
+            .assert()
+            .failure()
+            .stderr(
+                "Status: ERROR\n\
+                 Details: Failed to read CSS file 'tests/nonexistent.css': No such file or directory (os error 2)\n",
+            );
+    }
+
+    #[test]
+    fn extra_css() {
+        css_inline()
+            .arg("tests/example.html")
+            .arg("--extra-css=.test-class { background: green; }")
+            .arg("--output-filename-prefix=inlined.extra-css-cli.")
+            .assert()
+            .success()
+            .stdout("tests/example.html: SUCCESS\n");
+
+        let content = fs::read_to_string("tests/inlined.extra-css-cli.example.html").unwrap();
+        assert!(
+            content.contains(r#"style="color: #ffffff;background: green;""#),
+            "expected inline background from --extra-css but got:\n{}",
+            content
+        );
+    }
+
     #[test]
     fn not_found() {
         css_inline().arg("unknown.html").assert().failure().stderr(