fallow_extract/
css.rs

1//! CSS/SCSS file parsing and CSS Module class name extraction.
2//!
3//! Handles `@import`, `@use`, `@forward`, `@apply`, `@tailwind` directives,
4//! and extracts class names as named exports from `.module.css`/`.module.scss` files.
5
6use std::path::Path;
7use std::sync::LazyLock;
8
9use oxc_span::Span;
10
11use crate::{ExportInfo, ExportName, ImportInfo, ImportedName, ModuleInfo};
12use fallow_types::discover::FileId;
13
14/// Regex to extract CSS @import sources.
15/// Matches: @import "path"; @import 'path'; @import url("path"); @import url('path'); @import url(path);
16static CSS_IMPORT_RE: LazyLock<regex::Regex> = LazyLock::new(|| {
17    regex::Regex::new(r#"@import\s+(?:url\(\s*(?:["']([^"']+)["']|([^)]+))\s*\)|["']([^"']+)["'])"#)
18        .expect("valid regex")
19});
20
21/// Regex to extract SCSS @use and @forward sources.
22/// Matches: @use "path"; @use 'path'; @forward "path"; @forward 'path';
23static SCSS_USE_RE: LazyLock<regex::Regex> = LazyLock::new(|| {
24    regex::Regex::new(r#"@(?:use|forward)\s+["']([^"']+)["']"#).expect("valid regex")
25});
26
27/// Regex to extract @apply class references.
28/// Matches: @apply class1 class2 class3;
29static CSS_APPLY_RE: LazyLock<regex::Regex> =
30    LazyLock::new(|| regex::Regex::new(r"@apply\s+[^;}\n]+").expect("valid regex"));
31
32/// Regex to extract @tailwind directives.
33/// Matches: @tailwind base; @tailwind components; @tailwind utilities;
34static CSS_TAILWIND_RE: LazyLock<regex::Regex> =
35    LazyLock::new(|| regex::Regex::new(r"@tailwind\s+\w+").expect("valid regex"));
36
37/// Regex to match CSS block comments (`/* ... */`) for stripping before extraction.
38static CSS_COMMENT_RE: LazyLock<regex::Regex> =
39    LazyLock::new(|| regex::Regex::new(r"(?s)/\*.*?\*/").expect("valid regex"));
40
41/// Regex to match SCSS single-line comments (`// ...`) for stripping before extraction.
42static SCSS_LINE_COMMENT_RE: LazyLock<regex::Regex> =
43    LazyLock::new(|| regex::Regex::new(r"//[^\n]*").expect("valid regex"));
44
45/// Regex to extract CSS class names from selectors.
46/// Matches `.className` in selectors. Applied after stripping comments, strings, and URLs.
47static CSS_CLASS_RE: LazyLock<regex::Regex> =
48    LazyLock::new(|| regex::Regex::new(r"\.([a-zA-Z_][a-zA-Z0-9_-]*)").expect("valid regex"));
49
50/// Regex to strip quoted strings and `url(...)` content from CSS before class extraction.
51/// Prevents false positives from `content: ".foo"` and `url(./path/file.ext)`.
52static CSS_NON_SELECTOR_RE: LazyLock<regex::Regex> = LazyLock::new(|| {
53    regex::Regex::new(r#"(?s)"[^"]*"|'[^']*'|url\([^)]*\)"#).expect("valid regex")
54});
55
56pub(crate) fn is_css_file(path: &Path) -> bool {
57    path.extension()
58        .and_then(|e| e.to_str())
59        .is_some_and(|ext| ext == "css" || ext == "scss")
60}
61
62fn is_css_module_file(path: &Path) -> bool {
63    is_css_file(path)
64        && path
65            .file_stem()
66            .and_then(|s| s.to_str())
67            .is_some_and(|stem| stem.ends_with(".module"))
68}
69
70/// Returns true if a CSS import source is a remote URL or data URI that should be skipped.
71fn is_css_url_import(source: &str) -> bool {
72    source.starts_with("http://") || source.starts_with("https://") || source.starts_with("data:")
73}
74
75/// Normalize a CSS/SCSS import path to use `./` prefix for relative paths.
76/// CSS/SCSS resolve imports without `./` prefix as relative by default,
77/// unlike JS where unprefixed specifiers are bare (npm) specifiers.
78/// Only applies to paths with CSS/SCSS extensions — extensionless imports
79/// like `@import "tailwindcss"` are actual npm package imports.
80fn normalize_css_import_path(path: String) -> String {
81    if path.starts_with('.') || path.starts_with('/') || path.contains("://") {
82        return path;
83    }
84    // Paths with CSS/SCSS extensions are relative file imports
85    let ext = std::path::Path::new(&path)
86        .extension()
87        .and_then(|e| e.to_str());
88    match ext {
89        Some(e)
90            if e.eq_ignore_ascii_case("css")
91                || e.eq_ignore_ascii_case("scss")
92                || e.eq_ignore_ascii_case("sass")
93                || e.eq_ignore_ascii_case("less") =>
94        {
95            format!("./{path}")
96        }
97        _ => path,
98    }
99}
100
101/// Strip comments from CSS/SCSS source to avoid matching directives inside comments.
102fn strip_css_comments(source: &str, is_scss: bool) -> String {
103    let stripped = CSS_COMMENT_RE.replace_all(source, "");
104    if is_scss {
105        SCSS_LINE_COMMENT_RE.replace_all(&stripped, "").into_owned()
106    } else {
107        stripped.into_owned()
108    }
109}
110
111/// Extract class names from a CSS module file as named exports.
112pub fn extract_css_module_exports(source: &str) -> Vec<ExportInfo> {
113    let cleaned = CSS_NON_SELECTOR_RE.replace_all(source, "");
114    let mut seen = rustc_hash::FxHashSet::default();
115    let mut exports = Vec::new();
116    for cap in CSS_CLASS_RE.captures_iter(&cleaned) {
117        if let Some(m) = cap.get(1) {
118            let class_name = m.as_str().to_string();
119            if seen.insert(class_name.clone()) {
120                exports.push(ExportInfo {
121                    name: ExportName::Named(class_name),
122                    local_name: None,
123                    is_type_only: false,
124                    is_public: false,
125                    span: Span::default(),
126                    members: Vec::new(),
127                });
128            }
129        }
130    }
131    exports
132}
133
134/// Parse a CSS/SCSS file, extracting @import, @use, @forward, @apply, and @tailwind directives.
135pub(crate) fn parse_css_to_module(
136    file_id: FileId,
137    path: &Path,
138    source: &str,
139    content_hash: u64,
140) -> ModuleInfo {
141    let suppressions = crate::suppress::parse_suppressions_from_source(source);
142    let is_scss = path
143        .extension()
144        .and_then(|e| e.to_str())
145        .is_some_and(|ext| ext == "scss");
146
147    // Strip comments before matching to avoid false positives from commented-out code.
148    let stripped = strip_css_comments(source, is_scss);
149
150    let mut imports = Vec::new();
151
152    // Extract @import statements
153    for cap in CSS_IMPORT_RE.captures_iter(&stripped) {
154        let source_path = cap
155            .get(1)
156            .or_else(|| cap.get(2))
157            .or_else(|| cap.get(3))
158            .map(|m| m.as_str().trim().to_string());
159        if let Some(src) = source_path
160            && !src.is_empty()
161            && !is_css_url_import(&src)
162        {
163            // CSS/SCSS @import resolves relative paths without ./ prefix,
164            // so normalize to ./ to avoid bare-specifier misclassification
165            let src = normalize_css_import_path(src);
166            imports.push(ImportInfo {
167                source: src,
168                imported_name: ImportedName::SideEffect,
169                local_name: String::new(),
170                is_type_only: false,
171                span: Span::default(),
172            });
173        }
174    }
175
176    // Extract SCSS @use/@forward statements
177    if is_scss {
178        for cap in SCSS_USE_RE.captures_iter(&stripped) {
179            if let Some(m) = cap.get(1) {
180                imports.push(ImportInfo {
181                    source: normalize_css_import_path(m.as_str().to_string()),
182                    imported_name: ImportedName::SideEffect,
183                    local_name: String::new(),
184                    is_type_only: false,
185                    span: Span::default(),
186                });
187            }
188        }
189    }
190
191    // If @apply or @tailwind directives exist, create a synthetic import to tailwindcss
192    // to mark the dependency as used
193    let has_apply = CSS_APPLY_RE.is_match(&stripped);
194    let has_tailwind = CSS_TAILWIND_RE.is_match(&stripped);
195    if has_apply || has_tailwind {
196        imports.push(ImportInfo {
197            source: "tailwindcss".to_string(),
198            imported_name: ImportedName::SideEffect,
199            local_name: String::new(),
200            is_type_only: false,
201            span: Span::default(),
202        });
203    }
204
205    // For CSS module files, extract class names as named exports
206    let exports = if is_css_module_file(path) {
207        extract_css_module_exports(&stripped)
208    } else {
209        Vec::new()
210    };
211
212    ModuleInfo {
213        file_id,
214        exports,
215        imports,
216        re_exports: Vec::new(),
217        dynamic_imports: Vec::new(),
218        dynamic_import_patterns: Vec::new(),
219        require_calls: Vec::new(),
220        member_accesses: Vec::new(),
221        whole_object_uses: Vec::new(),
222        has_cjs_exports: false,
223        content_hash,
224        suppressions,
225        unused_import_bindings: Vec::new(),
226        line_offsets: fallow_types::extract::compute_line_offsets(source),
227    }
228}
229
230#[cfg(test)]
231mod tests {
232    use super::*;
233
234    /// Helper to collect export names as strings from `extract_css_module_exports`.
235    fn export_names(source: &str) -> Vec<String> {
236        extract_css_module_exports(source)
237            .into_iter()
238            .filter_map(|e| match e.name {
239                ExportName::Named(n) => Some(n),
240                _ => None,
241            })
242            .collect()
243    }
244
245    // ── is_css_file ──────────────────────────────────────────────
246
247    #[test]
248    fn is_css_file_css() {
249        assert!(is_css_file(Path::new("styles.css")));
250    }
251
252    #[test]
253    fn is_css_file_scss() {
254        assert!(is_css_file(Path::new("styles.scss")));
255    }
256
257    #[test]
258    fn is_css_file_rejects_js() {
259        assert!(!is_css_file(Path::new("app.js")));
260    }
261
262    #[test]
263    fn is_css_file_rejects_ts() {
264        assert!(!is_css_file(Path::new("app.ts")));
265    }
266
267    #[test]
268    fn is_css_file_rejects_less() {
269        assert!(!is_css_file(Path::new("styles.less")));
270    }
271
272    #[test]
273    fn is_css_file_rejects_no_extension() {
274        assert!(!is_css_file(Path::new("Makefile")));
275    }
276
277    // ── is_css_module_file ───────────────────────────────────────
278
279    #[test]
280    fn is_css_module_file_module_css() {
281        assert!(is_css_module_file(Path::new("Component.module.css")));
282    }
283
284    #[test]
285    fn is_css_module_file_module_scss() {
286        assert!(is_css_module_file(Path::new("Component.module.scss")));
287    }
288
289    #[test]
290    fn is_css_module_file_rejects_plain_css() {
291        assert!(!is_css_module_file(Path::new("styles.css")));
292    }
293
294    #[test]
295    fn is_css_module_file_rejects_plain_scss() {
296        assert!(!is_css_module_file(Path::new("styles.scss")));
297    }
298
299    #[test]
300    fn is_css_module_file_rejects_module_js() {
301        assert!(!is_css_module_file(Path::new("utils.module.js")));
302    }
303
304    // ── extract_css_module_exports: basic class extraction ───────
305
306    #[test]
307    fn extracts_single_class() {
308        let names = export_names(".foo { color: red; }");
309        assert_eq!(names, vec!["foo"]);
310    }
311
312    #[test]
313    fn extracts_multiple_classes() {
314        let names = export_names(".foo { } .bar { }");
315        assert_eq!(names, vec!["foo", "bar"]);
316    }
317
318    #[test]
319    fn extracts_nested_classes() {
320        let names = export_names(".foo .bar { color: red; }");
321        assert!(names.contains(&"foo".to_string()));
322        assert!(names.contains(&"bar".to_string()));
323    }
324
325    #[test]
326    fn extracts_hyphenated_class() {
327        let names = export_names(".my-class { }");
328        assert_eq!(names, vec!["my-class"]);
329    }
330
331    #[test]
332    fn extracts_camel_case_class() {
333        let names = export_names(".myClass { }");
334        assert_eq!(names, vec!["myClass"]);
335    }
336
337    #[test]
338    fn extracts_underscore_class() {
339        let names = export_names("._hidden { } .__wrapper { }");
340        assert!(names.contains(&"_hidden".to_string()));
341        assert!(names.contains(&"__wrapper".to_string()));
342    }
343
344    // ── Pseudo-selectors ─────────────────────────────────────────
345
346    #[test]
347    fn pseudo_selector_hover() {
348        let names = export_names(".foo:hover { color: blue; }");
349        assert_eq!(names, vec!["foo"]);
350    }
351
352    #[test]
353    fn pseudo_selector_focus() {
354        let names = export_names(".input:focus { outline: none; }");
355        assert_eq!(names, vec!["input"]);
356    }
357
358    #[test]
359    fn pseudo_element_before() {
360        let names = export_names(".icon::before { content: ''; }");
361        assert_eq!(names, vec!["icon"]);
362    }
363
364    #[test]
365    fn combined_pseudo_selectors() {
366        let names = export_names(".btn:hover, .btn:active, .btn:focus { }");
367        // "btn" should be deduplicated
368        assert_eq!(names, vec!["btn"]);
369    }
370
371    // ── Media queries ────────────────────────────────────────────
372
373    #[test]
374    fn classes_inside_media_query() {
375        let names = export_names(
376            "@media (max-width: 768px) { .mobile-nav { display: block; } .desktop-nav { display: none; } }",
377        );
378        assert!(names.contains(&"mobile-nav".to_string()));
379        assert!(names.contains(&"desktop-nav".to_string()));
380    }
381
382    // ── Deduplication ────────────────────────────────────────────
383
384    #[test]
385    fn deduplicates_repeated_class() {
386        let names = export_names(".btn { color: red; } .btn { font-size: 14px; }");
387        assert_eq!(names.iter().filter(|n| *n == "btn").count(), 1);
388    }
389
390    // ── Edge cases ───────────────────────────────────────────────
391
392    #[test]
393    fn empty_source() {
394        let names = export_names("");
395        assert!(names.is_empty());
396    }
397
398    #[test]
399    fn no_classes() {
400        let names = export_names("body { margin: 0; } * { box-sizing: border-box; }");
401        assert!(names.is_empty());
402    }
403
404    #[test]
405    fn ignores_classes_in_block_comments() {
406        // Note: extract_css_module_exports itself does NOT strip comments;
407        // comments are stripped in parse_css_to_module before calling it.
408        // But CSS_NON_SELECTOR_RE strips quoted strings. Testing the
409        // strip_css_comments + extract pipeline via the stripped source:
410        let stripped = strip_css_comments("/* .fake { } */ .real { }", false);
411        let names = export_names(&stripped);
412        assert!(!names.contains(&"fake".to_string()));
413        assert!(names.contains(&"real".to_string()));
414    }
415
416    #[test]
417    fn ignores_classes_in_strings() {
418        let names = export_names(r#".real { content: ".fake"; }"#);
419        assert!(names.contains(&"real".to_string()));
420        assert!(!names.contains(&"fake".to_string()));
421    }
422
423    #[test]
424    fn ignores_classes_in_url() {
425        let names = export_names(".real { background: url(./images/hero.png); }");
426        assert!(names.contains(&"real".to_string()));
427        // "png" from "hero.png" should not be extracted
428        assert!(!names.contains(&"png".to_string()));
429    }
430
431    // ── strip_css_comments ───────────────────────────────────────
432
433    #[test]
434    fn strip_css_block_comment() {
435        let result = strip_css_comments("/* removed */ .kept { }", false);
436        assert!(!result.contains("removed"));
437        assert!(result.contains(".kept"));
438    }
439
440    #[test]
441    fn strip_scss_line_comment() {
442        let result = strip_css_comments("// removed\n.kept { }", true);
443        assert!(!result.contains("removed"));
444        assert!(result.contains(".kept"));
445    }
446
447    #[test]
448    fn strip_scss_preserves_css_outside_comments() {
449        let source = "// line comment\n/* block comment */\n.visible { color: red; }";
450        let result = strip_css_comments(source, true);
451        assert!(result.contains(".visible"));
452    }
453
454    // ── is_css_url_import ────────────────────────────────────────
455
456    #[test]
457    fn url_import_http() {
458        assert!(is_css_url_import("http://example.com/style.css"));
459    }
460
461    #[test]
462    fn url_import_https() {
463        assert!(is_css_url_import("https://fonts.googleapis.com/css"));
464    }
465
466    #[test]
467    fn url_import_data() {
468        assert!(is_css_url_import("data:text/css;base64,abc"));
469    }
470
471    #[test]
472    fn url_import_local_not_skipped() {
473        assert!(!is_css_url_import("./local.css"));
474    }
475
476    #[test]
477    fn url_import_bare_specifier_not_skipped() {
478        assert!(!is_css_url_import("tailwindcss"));
479    }
480}
fallow_extract/css.rs

fallow_extract/
css.rs
