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        complexity: Vec::new(),
228    }
229}
230
231#[cfg(test)]
232mod tests {
233    use super::*;
234
235    /// Helper to collect export names as strings from `extract_css_module_exports`.
236    fn export_names(source: &str) -> Vec<String> {
237        extract_css_module_exports(source)
238            .into_iter()
239            .filter_map(|e| match e.name {
240                ExportName::Named(n) => Some(n),
241                _ => None,
242            })
243            .collect()
244    }
245
246    // ── is_css_file ──────────────────────────────────────────────
247
248    #[test]
249    fn is_css_file_css() {
250        assert!(is_css_file(Path::new("styles.css")));
251    }
252
253    #[test]
254    fn is_css_file_scss() {
255        assert!(is_css_file(Path::new("styles.scss")));
256    }
257
258    #[test]
259    fn is_css_file_rejects_js() {
260        assert!(!is_css_file(Path::new("app.js")));
261    }
262
263    #[test]
264    fn is_css_file_rejects_ts() {
265        assert!(!is_css_file(Path::new("app.ts")));
266    }
267
268    #[test]
269    fn is_css_file_rejects_less() {
270        assert!(!is_css_file(Path::new("styles.less")));
271    }
272
273    #[test]
274    fn is_css_file_rejects_no_extension() {
275        assert!(!is_css_file(Path::new("Makefile")));
276    }
277
278    // ── is_css_module_file ───────────────────────────────────────
279
280    #[test]
281    fn is_css_module_file_module_css() {
282        assert!(is_css_module_file(Path::new("Component.module.css")));
283    }
284
285    #[test]
286    fn is_css_module_file_module_scss() {
287        assert!(is_css_module_file(Path::new("Component.module.scss")));
288    }
289
290    #[test]
291    fn is_css_module_file_rejects_plain_css() {
292        assert!(!is_css_module_file(Path::new("styles.css")));
293    }
294
295    #[test]
296    fn is_css_module_file_rejects_plain_scss() {
297        assert!(!is_css_module_file(Path::new("styles.scss")));
298    }
299
300    #[test]
301    fn is_css_module_file_rejects_module_js() {
302        assert!(!is_css_module_file(Path::new("utils.module.js")));
303    }
304
305    // ── extract_css_module_exports: basic class extraction ───────
306
307    #[test]
308    fn extracts_single_class() {
309        let names = export_names(".foo { color: red; }");
310        assert_eq!(names, vec!["foo"]);
311    }
312
313    #[test]
314    fn extracts_multiple_classes() {
315        let names = export_names(".foo { } .bar { }");
316        assert_eq!(names, vec!["foo", "bar"]);
317    }
318
319    #[test]
320    fn extracts_nested_classes() {
321        let names = export_names(".foo .bar { color: red; }");
322        assert!(names.contains(&"foo".to_string()));
323        assert!(names.contains(&"bar".to_string()));
324    }
325
326    #[test]
327    fn extracts_hyphenated_class() {
328        let names = export_names(".my-class { }");
329        assert_eq!(names, vec!["my-class"]);
330    }
331
332    #[test]
333    fn extracts_camel_case_class() {
334        let names = export_names(".myClass { }");
335        assert_eq!(names, vec!["myClass"]);
336    }
337
338    #[test]
339    fn extracts_underscore_class() {
340        let names = export_names("._hidden { } .__wrapper { }");
341        assert!(names.contains(&"_hidden".to_string()));
342        assert!(names.contains(&"__wrapper".to_string()));
343    }
344
345    // ── Pseudo-selectors ─────────────────────────────────────────
346
347    #[test]
348    fn pseudo_selector_hover() {
349        let names = export_names(".foo:hover { color: blue; }");
350        assert_eq!(names, vec!["foo"]);
351    }
352
353    #[test]
354    fn pseudo_selector_focus() {
355        let names = export_names(".input:focus { outline: none; }");
356        assert_eq!(names, vec!["input"]);
357    }
358
359    #[test]
360    fn pseudo_element_before() {
361        let names = export_names(".icon::before { content: ''; }");
362        assert_eq!(names, vec!["icon"]);
363    }
364
365    #[test]
366    fn combined_pseudo_selectors() {
367        let names = export_names(".btn:hover, .btn:active, .btn:focus { }");
368        // "btn" should be deduplicated
369        assert_eq!(names, vec!["btn"]);
370    }
371
372    // ── Media queries ────────────────────────────────────────────
373
374    #[test]
375    fn classes_inside_media_query() {
376        let names = export_names(
377            "@media (max-width: 768px) { .mobile-nav { display: block; } .desktop-nav { display: none; } }",
378        );
379        assert!(names.contains(&"mobile-nav".to_string()));
380        assert!(names.contains(&"desktop-nav".to_string()));
381    }
382
383    // ── Deduplication ────────────────────────────────────────────
384
385    #[test]
386    fn deduplicates_repeated_class() {
387        let names = export_names(".btn { color: red; } .btn { font-size: 14px; }");
388        assert_eq!(names.iter().filter(|n| *n == "btn").count(), 1);
389    }
390
391    // ── Edge cases ───────────────────────────────────────────────
392
393    #[test]
394    fn empty_source() {
395        let names = export_names("");
396        assert!(names.is_empty());
397    }
398
399    #[test]
400    fn no_classes() {
401        let names = export_names("body { margin: 0; } * { box-sizing: border-box; }");
402        assert!(names.is_empty());
403    }
404
405    #[test]
406    fn ignores_classes_in_block_comments() {
407        // Note: extract_css_module_exports itself does NOT strip comments;
408        // comments are stripped in parse_css_to_module before calling it.
409        // But CSS_NON_SELECTOR_RE strips quoted strings. Testing the
410        // strip_css_comments + extract pipeline via the stripped source:
411        let stripped = strip_css_comments("/* .fake { } */ .real { }", false);
412        let names = export_names(&stripped);
413        assert!(!names.contains(&"fake".to_string()));
414        assert!(names.contains(&"real".to_string()));
415    }
416
417    #[test]
418    fn ignores_classes_in_strings() {
419        let names = export_names(r#".real { content: ".fake"; }"#);
420        assert!(names.contains(&"real".to_string()));
421        assert!(!names.contains(&"fake".to_string()));
422    }
423
424    #[test]
425    fn ignores_classes_in_url() {
426        let names = export_names(".real { background: url(./images/hero.png); }");
427        assert!(names.contains(&"real".to_string()));
428        // "png" from "hero.png" should not be extracted
429        assert!(!names.contains(&"png".to_string()));
430    }
431
432    // ── strip_css_comments ───────────────────────────────────────
433
434    #[test]
435    fn strip_css_block_comment() {
436        let result = strip_css_comments("/* removed */ .kept { }", false);
437        assert!(!result.contains("removed"));
438        assert!(result.contains(".kept"));
439    }
440
441    #[test]
442    fn strip_scss_line_comment() {
443        let result = strip_css_comments("// removed\n.kept { }", true);
444        assert!(!result.contains("removed"));
445        assert!(result.contains(".kept"));
446    }
447
448    #[test]
449    fn strip_scss_preserves_css_outside_comments() {
450        let source = "// line comment\n/* block comment */\n.visible { color: red; }";
451        let result = strip_css_comments(source, true);
452        assert!(result.contains(".visible"));
453    }
454
455    // ── is_css_url_import ────────────────────────────────────────
456
457    #[test]
458    fn url_import_http() {
459        assert!(is_css_url_import("http://example.com/style.css"));
460    }
461
462    #[test]
463    fn url_import_https() {
464        assert!(is_css_url_import("https://fonts.googleapis.com/css"));
465    }
466
467    #[test]
468    fn url_import_data() {
469        assert!(is_css_url_import("data:text/css;base64,abc"));
470    }
471
472    #[test]
473    fn url_import_local_not_skipped() {
474        assert!(!is_css_url_import("./local.css"));
475    }
476
477    #[test]
478    fn url_import_bare_specifier_not_skipped() {
479        assert!(!is_css_url_import("tailwindcss"));
480    }
481}
fallow_extract/css.rs

fallow_extract/
css.rs
