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                    span: Span::default(),
125                    members: Vec::new(),
126                });
127            }
128        }
129    }
130    exports
131}
132
133/// Parse a CSS/SCSS file, extracting @import, @use, @forward, @apply, and @tailwind directives.
134pub(crate) fn parse_css_to_module(
135    file_id: FileId,
136    path: &Path,
137    source: &str,
138    content_hash: u64,
139) -> ModuleInfo {
140    let suppressions = crate::suppress::parse_suppressions_from_source(source);
141    let is_scss = path
142        .extension()
143        .and_then(|e| e.to_str())
144        .is_some_and(|ext| ext == "scss");
145
146    // Strip comments before matching to avoid false positives from commented-out code.
147    let stripped = strip_css_comments(source, is_scss);
148
149    let mut imports = Vec::new();
150
151    // Extract @import statements
152    for cap in CSS_IMPORT_RE.captures_iter(&stripped) {
153        let source_path = cap
154            .get(1)
155            .or_else(|| cap.get(2))
156            .or_else(|| cap.get(3))
157            .map(|m| m.as_str().trim().to_string());
158        if let Some(src) = source_path
159            && !src.is_empty()
160            && !is_css_url_import(&src)
161        {
162            // CSS/SCSS @import resolves relative paths without ./ prefix,
163            // so normalize to ./ to avoid bare-specifier misclassification
164            let src = normalize_css_import_path(src);
165            imports.push(ImportInfo {
166                source: src,
167                imported_name: ImportedName::SideEffect,
168                local_name: String::new(),
169                is_type_only: false,
170                span: Span::default(),
171            });
172        }
173    }
174
175    // Extract SCSS @use/@forward statements
176    if is_scss {
177        for cap in SCSS_USE_RE.captures_iter(&stripped) {
178            if let Some(m) = cap.get(1) {
179                imports.push(ImportInfo {
180                    source: normalize_css_import_path(m.as_str().to_string()),
181                    imported_name: ImportedName::SideEffect,
182                    local_name: String::new(),
183                    is_type_only: false,
184                    span: Span::default(),
185                });
186            }
187        }
188    }
189
190    // If @apply or @tailwind directives exist, create a synthetic import to tailwindcss
191    // to mark the dependency as used
192    let has_apply = CSS_APPLY_RE.is_match(&stripped);
193    let has_tailwind = CSS_TAILWIND_RE.is_match(&stripped);
194    if has_apply || has_tailwind {
195        imports.push(ImportInfo {
196            source: "tailwindcss".to_string(),
197            imported_name: ImportedName::SideEffect,
198            local_name: String::new(),
199            is_type_only: false,
200            span: Span::default(),
201        });
202    }
203
204    // For CSS module files, extract class names as named exports
205    let exports = if is_css_module_file(path) {
206        extract_css_module_exports(&stripped)
207    } else {
208        Vec::new()
209    };
210
211    ModuleInfo {
212        file_id,
213        exports,
214        imports,
215        re_exports: Vec::new(),
216        dynamic_imports: Vec::new(),
217        dynamic_import_patterns: Vec::new(),
218        require_calls: Vec::new(),
219        member_accesses: Vec::new(),
220        whole_object_uses: Vec::new(),
221        has_cjs_exports: false,
222        content_hash,
223        suppressions,
224        unused_import_bindings: Vec::new(),
225        line_offsets: fallow_types::extract::compute_line_offsets(source),
226    }
227}
228
229#[cfg(test)]
230mod tests {
231    use super::*;
232
233    /// Helper to collect export names as strings from `extract_css_module_exports`.
234    fn export_names(source: &str) -> Vec<String> {
235        extract_css_module_exports(source)
236            .into_iter()
237            .filter_map(|e| match e.name {
238                ExportName::Named(n) => Some(n),
239                _ => None,
240            })
241            .collect()
242    }
243
244    // ── is_css_file ──────────────────────────────────────────────
245
246    #[test]
247    fn is_css_file_css() {
248        assert!(is_css_file(Path::new("styles.css")));
249    }
250
251    #[test]
252    fn is_css_file_scss() {
253        assert!(is_css_file(Path::new("styles.scss")));
254    }
255
256    #[test]
257    fn is_css_file_rejects_js() {
258        assert!(!is_css_file(Path::new("app.js")));
259    }
260
261    #[test]
262    fn is_css_file_rejects_ts() {
263        assert!(!is_css_file(Path::new("app.ts")));
264    }
265
266    #[test]
267    fn is_css_file_rejects_less() {
268        assert!(!is_css_file(Path::new("styles.less")));
269    }
270
271    #[test]
272    fn is_css_file_rejects_no_extension() {
273        assert!(!is_css_file(Path::new("Makefile")));
274    }
275
276    // ── is_css_module_file ───────────────────────────────────────
277
278    #[test]
279    fn is_css_module_file_module_css() {
280        assert!(is_css_module_file(Path::new("Component.module.css")));
281    }
282
283    #[test]
284    fn is_css_module_file_module_scss() {
285        assert!(is_css_module_file(Path::new("Component.module.scss")));
286    }
287
288    #[test]
289    fn is_css_module_file_rejects_plain_css() {
290        assert!(!is_css_module_file(Path::new("styles.css")));
291    }
292
293    #[test]
294    fn is_css_module_file_rejects_plain_scss() {
295        assert!(!is_css_module_file(Path::new("styles.scss")));
296    }
297
298    #[test]
299    fn is_css_module_file_rejects_module_js() {
300        assert!(!is_css_module_file(Path::new("utils.module.js")));
301    }
302
303    // ── extract_css_module_exports: basic class extraction ───────
304
305    #[test]
306    fn extracts_single_class() {
307        let names = export_names(".foo { color: red; }");
308        assert_eq!(names, vec!["foo"]);
309    }
310
311    #[test]
312    fn extracts_multiple_classes() {
313        let names = export_names(".foo { } .bar { }");
314        assert_eq!(names, vec!["foo", "bar"]);
315    }
316
317    #[test]
318    fn extracts_nested_classes() {
319        let names = export_names(".foo .bar { color: red; }");
320        assert!(names.contains(&"foo".to_string()));
321        assert!(names.contains(&"bar".to_string()));
322    }
323
324    #[test]
325    fn extracts_hyphenated_class() {
326        let names = export_names(".my-class { }");
327        assert_eq!(names, vec!["my-class"]);
328    }
329
330    #[test]
331    fn extracts_camel_case_class() {
332        let names = export_names(".myClass { }");
333        assert_eq!(names, vec!["myClass"]);
334    }
335
336    #[test]
337    fn extracts_underscore_class() {
338        let names = export_names("._hidden { } .__wrapper { }");
339        assert!(names.contains(&"_hidden".to_string()));
340        assert!(names.contains(&"__wrapper".to_string()));
341    }
342
343    // ── Pseudo-selectors ─────────────────────────────────────────
344
345    #[test]
346    fn pseudo_selector_hover() {
347        let names = export_names(".foo:hover { color: blue; }");
348        assert_eq!(names, vec!["foo"]);
349    }
350
351    #[test]
352    fn pseudo_selector_focus() {
353        let names = export_names(".input:focus { outline: none; }");
354        assert_eq!(names, vec!["input"]);
355    }
356
357    #[test]
358    fn pseudo_element_before() {
359        let names = export_names(".icon::before { content: ''; }");
360        assert_eq!(names, vec!["icon"]);
361    }
362
363    #[test]
364    fn combined_pseudo_selectors() {
365        let names = export_names(".btn:hover, .btn:active, .btn:focus { }");
366        // "btn" should be deduplicated
367        assert_eq!(names, vec!["btn"]);
368    }
369
370    // ── Media queries ────────────────────────────────────────────
371
372    #[test]
373    fn classes_inside_media_query() {
374        let names = export_names(
375            "@media (max-width: 768px) { .mobile-nav { display: block; } .desktop-nav { display: none; } }",
376        );
377        assert!(names.contains(&"mobile-nav".to_string()));
378        assert!(names.contains(&"desktop-nav".to_string()));
379    }
380
381    // ── Deduplication ────────────────────────────────────────────
382
383    #[test]
384    fn deduplicates_repeated_class() {
385        let names = export_names(".btn { color: red; } .btn { font-size: 14px; }");
386        assert_eq!(names.iter().filter(|n| *n == "btn").count(), 1);
387    }
388
389    // ── Edge cases ───────────────────────────────────────────────
390
391    #[test]
392    fn empty_source() {
393        let names = export_names("");
394        assert!(names.is_empty());
395    }
396
397    #[test]
398    fn no_classes() {
399        let names = export_names("body { margin: 0; } * { box-sizing: border-box; }");
400        assert!(names.is_empty());
401    }
402
403    #[test]
404    fn ignores_classes_in_block_comments() {
405        // Note: extract_css_module_exports itself does NOT strip comments;
406        // comments are stripped in parse_css_to_module before calling it.
407        // But CSS_NON_SELECTOR_RE strips quoted strings. Testing the
408        // strip_css_comments + extract pipeline via the stripped source:
409        let stripped = strip_css_comments("/* .fake { } */ .real { }", false);
410        let names = export_names(&stripped);
411        assert!(!names.contains(&"fake".to_string()));
412        assert!(names.contains(&"real".to_string()));
413    }
414
415    #[test]
416    fn ignores_classes_in_strings() {
417        let names = export_names(r#".real { content: ".fake"; }"#);
418        assert!(names.contains(&"real".to_string()));
419        assert!(!names.contains(&"fake".to_string()));
420    }
421
422    #[test]
423    fn ignores_classes_in_url() {
424        let names = export_names(".real { background: url(./images/hero.png); }");
425        assert!(names.contains(&"real".to_string()));
426        // "png" from "hero.png" should not be extracted
427        assert!(!names.contains(&"png".to_string()));
428    }
429
430    // ── strip_css_comments ───────────────────────────────────────
431
432    #[test]
433    fn strip_css_block_comment() {
434        let result = strip_css_comments("/* removed */ .kept { }", false);
435        assert!(!result.contains("removed"));
436        assert!(result.contains(".kept"));
437    }
438
439    #[test]
440    fn strip_scss_line_comment() {
441        let result = strip_css_comments("// removed\n.kept { }", true);
442        assert!(!result.contains("removed"));
443        assert!(result.contains(".kept"));
444    }
445
446    #[test]
447    fn strip_scss_preserves_css_outside_comments() {
448        let source = "// line comment\n/* block comment */\n.visible { color: red; }";
449        let result = strip_css_comments(source, true);
450        assert!(result.contains(".visible"));
451    }
452
453    // ── is_css_url_import ────────────────────────────────────────
454
455    #[test]
456    fn url_import_http() {
457        assert!(is_css_url_import("http://example.com/style.css"));
458    }
459
460    #[test]
461    fn url_import_https() {
462        assert!(is_css_url_import("https://fonts.googleapis.com/css"));
463    }
464
465    #[test]
466    fn url_import_data() {
467        assert!(is_css_url_import("data:text/css;base64,abc"));
468    }
469
470    #[test]
471    fn url_import_local_not_skipped() {
472        assert!(!is_css_url_import("./local.css"));
473    }
474
475    #[test]
476    fn url_import_bare_specifier_not_skipped() {
477        assert!(!is_css_url_import("tailwindcss"));
478    }
479}
fallow_extract/css.rs

fallow_extract/
css.rs
