Add projectRoot option and use relative paths for CSS module hashes

Fixes #355

Cargo.toml

@@ -37,9 +37,9 @@ parcel_sourcemap = { version = "2.1.1", features = ["json"] }
 data-encoding = "2.3.2"
 lazy_static = "1.4.0"
 const-str = "0.3.1"
+pathdiff = "0.2.1"
 # CLI deps
 clap = { version = "3.0.6", features = ["derive"], optional = true }
-pathdiff = { version = "0.2.1", optional = true }
 browserslist-rs = { version = "0.7.0", optional = true }
 rayon = "1.5.1"
 dashmap = "5.0.0"
@@ -59,7 +59,7 @@ serde_json = "1"
 [features]
 default = ["grid"]
 browserslist = ["browserslist-rs"]
-cli = ["clap", "serde_json", "pathdiff", "browserslist", "jemallocator"]
+cli = ["clap", "serde_json", "browserslist", "jemallocator"]
 grid = []
 serde = ["smallvec/serde", "cssparser/serde"]
 

c/src/lib.rs

@@ -195,6 +195,7 @@ pub struct ToCssOptions {
   source_map: bool,
   input_source_map: *const c_char,
   input_source_map_len: usize,
+  project_root: *const c_char,
   targets: Targets,
   analyze_dependencies: bool,
   pseudo_classes: PseudoClasses,
@@ -284,7 +285,7 @@ pub extern "C" fn lightningcss_stylesheet_parse(
     error_recovery: options.error_recovery,
     source_index: 0,
     warnings: Some(warnings.clone()),
-    at_rule_parser: None
+    at_rule_parser: None,
   };
 
   let stylesheet = unwrap!(StyleSheet::parse(code, opts), error, std::ptr::null_mut());
@@ -324,6 +325,11 @@ pub extern "C" fn lightningcss_stylesheet_to_css(
 
   let opts = PrinterOptions {
     minify: options.minify,
+    project_root: if options.project_root.is_null() {
+      None
+    } else {
+      Some(unsafe { std::str::from_utf8_unchecked(CStr::from_ptr(options.project_root).to_bytes()) })
+    },
     source_map: source_map.as_mut(),
     targets: if options.targets != Targets::default() {
       Some(options.targets.into())

node/index.d.ts

@@ -11,6 +11,11 @@ export interface TransformOptions {
   sourceMap?: boolean,
   /** An input source map to extend. */
   inputSourceMap?: string,
+  /** 
+   * An optional project root path, used as the source root in the output source map.
+   * Also used to generate relative paths for sources used in CSS module hashes.
+   */
+  projectRoot?: string,
   /** The browser targets for the generated code. */
   targets?: Targets,
   /** Whether to enable various draft syntax. */

node/src/lib.rs

@@ -387,6 +387,7 @@ fn init(mut exports: JsObject) -> napi::Result<()> {
 #[serde(rename_all = "camelCase")]
 struct Config {
   pub filename: Option<String>,
+  pub project_root: Option<String>,
   #[serde(with = "serde_bytes")]
   pub code: Vec<u8>,
   pub targets: Option<Browsers>,
@@ -432,6 +433,7 @@ struct CssModulesConfig {
 #[serde(rename_all = "camelCase")]
 struct BundleConfig {
   pub filename: String,
+  pub project_root: Option<String>,
   pub targets: Option<Browsers>,
   pub minify: Option<bool>,
   pub source_map: Option<bool>,
@@ -479,8 +481,9 @@ fn compile<'i>(code: &'i str, config: &Config) -> Result<TransformResult<'i>, Co
   let warnings = Some(Arc::new(RwLock::new(Vec::new())));
 
   let filename = config.filename.clone().unwrap_or_default();
+  let project_root = config.project_root.as_ref().map(|p| p.as_ref());
   let mut source_map = if config.source_map.unwrap_or_default() {
-    let mut sm = SourceMap::new("/");
+    let mut sm = SourceMap::new(project_root.unwrap_or("/"));
     sm.add_source(&filename);
     sm.set_source_content(0, code)?;
     Some(sm)
@@ -528,6 +531,7 @@ fn compile<'i>(code: &'i str, config: &Config) -> Result<TransformResult<'i>, Co
     stylesheet.to_css(PrinterOptions {
       minify: config.minify.unwrap_or_default(),
       source_map: source_map.as_mut(),
+      project_root,
       targets: config.targets,
       analyze_dependencies: if let Some(d) = &config.analyze_dependencies {
         match d {
@@ -578,8 +582,9 @@ fn compile_bundle<'i, P: SourceProvider>(
   fs: &'i P,
   config: &BundleConfig,
 ) -> Result<TransformResult<'i>, CompileError<'i, P::Error>> {
+  let project_root = config.project_root.as_ref().map(|p| p.as_ref());
   let mut source_map = if config.source_map.unwrap_or_default() {
-    Some(SourceMap::new("/"))
+    Some(SourceMap::new(project_root.unwrap_or("/")))
   } else {
     None
   };
@@ -624,6 +629,7 @@ fn compile_bundle<'i, P: SourceProvider>(
     stylesheet.to_css(PrinterOptions {
       minify: config.minify.unwrap_or_default(),
       source_map: source_map.as_mut(),
+      project_root,
       targets: config.targets,
       analyze_dependencies: if let Some(d) = &config.analyze_dependencies {
         match d {
@@ -729,6 +735,7 @@ fn compile_attr<'i>(
     attr.to_css(PrinterOptions {
       minify: config.minify,
       source_map: None,
+      project_root: None,
       targets: config.targets,
       analyze_dependencies: if config.analyze_dependencies {
         Some(DependencyOptions::default())

src/bundler.rs

@@ -34,7 +34,8 @@ use crate::{
     layer::{LayerBlockRule, LayerName},
     Location,
   },
-  values::ident::DashedIdentReference, traits::ToCss,
+  traits::ToCss,
+  values::ident::DashedIdentReference,
 };
 use crate::{
   error::{Error, ParserError},
@@ -189,7 +190,7 @@ impl<'i, T: std::error::Error> BundleErrorKind<'i, T> {
 
 impl<'a, 'o, 's, P: SourceProvider, T: AtRuleParser<'a> + Clone + Sync + Send> Bundler<'a, 'o, 's, P, T>
 where
-   T::AtRule: Sync + Send + ToCss
+  T::AtRule: Sync + Send + ToCss,
 {
   /// Creates a new Bundler using the given source provider.
   /// If a source map is given, the content of each source file included in the bundle will
@@ -547,7 +548,11 @@ where
   fn order(&mut self) {
     process(self.stylesheets.get_mut().unwrap(), 0, &mut HashSet::new());
 
-    fn process<'i, T: AtRuleParser<'i>>(stylesheets: &mut Vec<BundleStyleSheet<'i, '_, T>>, source_index: u32, visited: &mut HashSet<u32>) {
+    fn process<'i, T: AtRuleParser<'i>>(
+      stylesheets: &mut Vec<BundleStyleSheet<'i, '_, T>>,
+      source_index: u32,
+      visited: &mut HashSet<u32>,
+    ) {
       if visited.contains(&source_index) {
         return;
       }
@@ -722,6 +727,7 @@ mod tests {
   use indoc::indoc;
   use std::collections::HashMap;
 
+  #[derive(Clone)]
   struct TestProvider {
     map: HashMap<PathBuf, String>,
   }
@@ -789,7 +795,11 @@ mod tests {
     stylesheet.to_css(PrinterOptions::default()).unwrap().code
   }
 
-  fn bundle_css_module<P: SourceProvider>(fs: P, entry: &str) -> (String, CssModuleExports) {
+  fn bundle_css_module<P: SourceProvider>(
+    fs: P,
+    entry: &str,
+    project_root: Option<&str>,
+  ) -> (String, CssModuleExports) {
     let mut bundler = Bundler::new(
       &fs,
       None,
@@ -803,7 +813,12 @@ mod tests {
     );
     let mut stylesheet = bundler.bundle(Path::new(entry)).unwrap();
     stylesheet.minify(MinifyOptions::default()).unwrap();
-    let res = stylesheet.to_css(PrinterOptions::default()).unwrap();
+    let res = stylesheet
+      .to_css(PrinterOptions {
+        project_root,
+        ..PrinterOptions::default()
+      })
+      .unwrap();
     (res.code, res.exports.unwrap())
   }
 
@@ -1688,6 +1703,7 @@ mod tests {
         },
       },
       "/a.css",
+      None,
     );
     assert_eq!(
       code,
@@ -1722,6 +1738,7 @@ mod tests {
         },
       },
       "/a.css",
+      None,
     );
     assert_eq!(
       code,
@@ -1763,6 +1780,7 @@ mod tests {
         },
       },
       "/a.css",
+      None,
     );
     assert_eq!(
       code,
@@ -1802,6 +1820,7 @@ mod tests {
         },
       },
       "/a.css",
+      None,
     );
     assert_eq!(
       code,
@@ -1824,6 +1843,59 @@ mod tests {
         "a" => "_6lixEq_a"
       }
     );
+
+    // Hashes are stable between project roots.
+    let expected = indoc! { r#"
+    .dyGcAa_b {
+      background: #ff0;
+    }
+
+    .CK9avG_a {
+      background: #fff;
+    }
+  "#};
+
+    let (code, _) = bundle_css_module(
+      TestProvider {
+        map: fs! {
+          "/foo/bar/a.css": r#"
+        @import "b.css";
+        .a {
+          background: white;
+        }
+      "#,
+          "/foo/bar/b.css": r#"
+        .b {
+          background: yellow;
+        }
+      "#
+        },
+      },
+      "/foo/bar/a.css",
+      Some("/foo/bar"),
+    );
+    assert_eq!(code, expected);
+
+    let (code, _) = bundle_css_module(
+      TestProvider {
+        map: fs! {
+          "/x/y/z/a.css": r#"
+      @import "b.css";
+      .a {
+        background: white;
+      }
+    "#,
+          "/x/y/z/b.css": r#"
+      .b {
+        background: yellow;
+      }
+    "#
+        },
+      },
+      "/x/y/z/a.css",
+      Some("/x/y/z"),
+    );
+    assert_eq!(code, expected);
   }
 
   #[test]

src/css_modules.rs

@@ -13,8 +13,10 @@ use crate::properties::css_modules::{Composes, Specifier};
 use crate::selector::SelectorList;
 use data_encoding::{Encoding, Specification};
 use lazy_static::lazy_static;
+use pathdiff::diff_paths;
 use serde::Serialize;
 use smallvec::{smallvec, SmallVec};
+use std::borrow::Cow;
 use std::collections::hash_map::DefaultHasher;
 use std::collections::HashMap;
 use std::fmt::Write;
@@ -224,16 +226,32 @@ impl<'a, 'b, 'c> CssModule<'a, 'b, 'c> {
   pub fn new(
     config: &'a Config<'b>,
     sources: &'c Vec<String>,
+    project_root: Option<&'c str>,
     references: &'a mut HashMap<String, CssModuleReference>,
   ) -> Self {
+    let project_root = project_root.map(|p| Path::new(p));
+    let sources: Vec<&Path> = sources.iter().map(|filename| Path::new(filename)).collect();
+    let hashes = sources
+      .iter()
+      .map(|path| {
+        // Make paths relative to project root so hashes are stable.
+        let source = match project_root {
+          Some(project_root) if path.is_absolute() => {
+            diff_paths(path, project_root).map_or(Cow::Borrowed(*path), Cow::Owned)
+          }
+          _ => Cow::Borrowed(*path),
+        };
+        hash(
+          &source.to_string_lossy(),
+          matches!(config.pattern.segments[0], Segment::Hash),
+        )
+      })
+      .collect();
     Self {
       config,
-      sources: sources.iter().map(|filename| Path::new(filename)).collect(),
-      hashes: sources
-        .iter()
-        .map(|source| hash(&source, matches!(config.pattern.segments[0], Segment::Hash)))
-        .collect(),
       exports_by_source_index: sources.iter().map(|_| HashMap::new()).collect(),
+      sources,
+      hashes,
       references,
     }
   }

src/lib.rs

@@ -20224,6 +20224,45 @@ mod tests {
         ..Default::default()
       },
     );
+
+    // Stable hashes between project roots.
+    fn test_project_root(project_root: &str, filename: &str, hash: &str) {
+      let stylesheet = StyleSheet::parse(
+        r#"
+        .foo {
+          background: red;
+        }
+        "#,
+        ParserOptions {
+          filename: filename.into(),
+          css_modules: Some(Default::default()),
+          ..ParserOptions::default()
+        },
+      )
+      .unwrap();
+      let res = stylesheet
+        .to_css(PrinterOptions {
+          project_root: Some(project_root),
+          ..PrinterOptions::default()
+        })
+        .unwrap();
+      assert_eq!(
+        res.code,
+        format!(
+          indoc! {r#"
+      .{}_foo {{
+        background: red;
+      }}
+      "#},
+          hash
+        )
+      );
+    }
+
+    test_project_root("/foo/bar", "/foo/bar/test.css", "EgL3uq");
+    test_project_root("/foo", "/foo/test.css", "EgL3uq");
+    test_project_root("/foo/bar", "/foo/bar/baz/test.css", "xLEkNW");
+    test_project_root("/foo", "/foo/baz/test.css", "xLEkNW");
   }
 
   #[test]