250 lines
12 KiB
TypeScript
250 lines
12 KiB
TypeScript
// floorViolations checks a stylesheet against FLOOR, the browser floor of README → "Two browser
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// floors", using MDN's compat data. A feature one of its engines lacks passes only inside an
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// `@supports` whose condition requires it; an at-rule or a nested rule the floor lacks fails even there.
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// Checked: at-rules, media features, pseudo-classes and -elements, properties, and, in a property's
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// value, its functions, its units and the keywords MDN lists for that property. A name MDN has no
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// entry for fails. A media feature the floor lacks passes, since an engine without it reads the query
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// as false; media range and `or` syntax fail. A partial implementation counts as support, since MDN
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// marks edge gaps that way, such as `outline` ignoring `border-radius` before Chrome 94. A
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// vendor-prefixed name is one engine's by design and is skipped, as are `font-family` names: an engine
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// skips a family it lacks.
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// Not checked: the body of an at-rule other than @media and @supports.
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import bcd from "@mdn/browser-compat-data" with { type: "json" };
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import type { CompatStatement, Identifier, SimpleSupportStatement, SupportBlock } from "@mdn/browser-compat-data";
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const FLOOR = [["chrome", "87"], ["safari", "15"], ["firefox", "115"]] as const;
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interface Feature {
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label: string;
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path: string | undefined;
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// Matches the feature in an `@supports` condition that tests for it.
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guard: RegExp;
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offset: number;
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}
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interface Sheet {
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css: string;
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out: string[];
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}
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export function floorViolations(css: string): string[] {
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const sheet = { css: blank(css), out: [] };
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const open = unclosed(sheet.css);
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if (open !== undefined) return [`line ${lineAt(sheet.css, open)}: ${sheet.css[open]} is never closed`];
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walk(sheet, 0, sheet.css.length, []);
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return [...new Set(sheet.out)];
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}
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// The innermost bracket nothing closes: a browser reads the rest of the sheet as inside it.
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function unclosed(css: string): number | undefined {
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const open: { at: number; closer: string }[] = [];
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for (let i = 0; i < css.length; i++) {
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if (css[i] === "{" || css[i] === "(") open.push({ at: i, closer: css[i] === "{" ? "}" : ")" });
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else if (css[i] === open.at(-1)?.closer) open.pop();
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}
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return open.at(-1)?.at;
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}
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const lineAt = (css: string, offset: number): number => css.slice(0, offset).split("\n").length;
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// Comments, string contents and url() contents become spaces, so nothing inside one reads as syntax
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// and every offset keeps its line.
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function blank(css: string): string {
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return css.replace(/\/\*[\s\S]*?\*\/|"(?:[^"\\\n]|\\.)*"|'(?:[^'\\\n]|\\.)*'|url\([^)]*\)/g, (m) => {
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if (m.startsWith("/*")) return m.replace(/[^\n]/g, " ");
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const keep = m.startsWith("url(") ? 4 : 1;
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return m.slice(0, keep) + " ".repeat(m.length - keep - 1) + m.slice(-1);
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});
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}
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// The end of `text` when nothing closes the bracket. floorViolations refuses a sheet with one left
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// open, so only an @supports condition cut at a `;` or `{` inside its parentheses gets there.
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function closing(text: string, open: number): number {
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const [opener, closer] = text[open] === "(" ? ["(", ")"] : ["{", "}"];
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let depth = 0;
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for (let i = open; i < text.length; i++) {
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if (text[i] === opener) depth++;
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if (text[i] === closer && --depth === 0) return i;
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}
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return text.length;
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}
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function walk(sheet: Sheet, start: number, end: number, guards: string[]): void {
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let i = start;
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while (i < end) {
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const stop = sheet.css.slice(i, end).search(/[{;]/);
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if (stop < 0) return;
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const at = i + stop;
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const raw = sheet.css.slice(i, at);
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const prelude = raw.trim();
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const offset = i + raw.length - raw.trimStart().length;
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const blockEnd = sheet.css[at] === "{" ? closing(sheet.css, at) : at;
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if (prelude.startsWith("@")) atRule(sheet, prelude, offset, guards, [at + 1, blockEnd]);
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else styleRule(sheet, prelude, offset, guards, [at + 1, blockEnd]);
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i = blockEnd + 1;
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}
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}
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function atRule(sheet: Sheet, prelude: string, offset: number, guards: string[], [from, to]: [number, number]): void {
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const name = /^@([\w-]+)/.exec(prelude)?.[1]?.toLowerCase() ?? "";
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if (name.startsWith("-")) return;
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check(sheet, guards, { label: `@${name}`, path: `css.at-rules.${name}`, guard: never, offset });
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const condition = prelude.slice(name.length + 1);
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if (name === "media") mediaQuery(sheet, guards, condition, offset);
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if (name === "supports" && /(?<![\w-])selector\(/i.test(condition)) {
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check(sheet, guards, { label: "selector()", path: "css.at-rules.supports.selector", guard: never, offset });
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}
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if (name === "media" || name === "supports") {
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walk(sheet, from, to, name === "supports" ? [...guards, positive(condition)] : guards);
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}
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}
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// Range and `or` syntax each have a floor spelling (`min-`/`max-`, a comma list), so a query using
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// one was meant for every engine, and a floor engine drops it whole.
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function mediaQuery(sheet: Sheet, guards: string[], condition: string, offset: number): void {
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for (const m of condition.matchAll(/\(\s*(?:min-|max-)?([a-z][\w-]*)\s*[:)]/gi)) {
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const path = `css.at-rules.media.${m[1]}`;
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if (!entry(path)) check(sheet, guards, { label: `(${m[1]})`, path, guard: never, offset });
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}
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if (/[<>=]/.test(condition)) {
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check(sheet, guards, { label: "media range syntax", path: "css.at-rules.media.range_syntax", guard: never, offset });
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}
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if (OR.test(condition)) {
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check(sheet, guards, { label: "media or syntax", path: "css.at-rules.media.or_syntax", guard: never, offset });
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}
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}
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// The parts of an @supports condition that must hold for its block to apply: neither a `not (…)`
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// group nor an operand of an `or`, at any depth.
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function positive(condition: string): string {
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let top = "";
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let kept = "";
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let from = 0;
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for (let open = condition.indexOf("("); open >= 0; open = condition.indexOf("(", from)) {
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const close = closing(condition, open);
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const head = condition.slice(from, open);
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const inner = condition.slice(open + 1, close);
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top += head;
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if (NEGATED.test(head)) kept += head.replace(NEGATED, "");
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else if (/[\w-]$/.test(head)) kept += `${head}(${inner})`; // a function such as selector()
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else kept += `${head}(${positive(inner)})`;
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from = close + 1;
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}
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return OR.test(top + condition.slice(from)) ? "" : kept + condition.slice(from);
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}
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const OR = /(?<![\w-])or\s/i;
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const NEGATED = /(?<![\w-])not\s+[\w-]*$/i;
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function styleRule(sheet: Sheet, selector: string, offset: number, guards: string[], [from, to]: [number, number]): void {
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for (const m of selector.matchAll(/::?([a-z][\w-]*)/gi)) {
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const name = (m[1] ?? "").toLowerCase();
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check(sheet, guards, { label: `:${name}`, path: `css.selectors.${name}`, guard: new RegExp(`:${name}(?![\\w-])`, "i"), offset: offset + (m.index ?? 0) });
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}
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const body = sheet.css.slice(from, to);
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if (body.includes("{")) {
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check(sheet, guards, { label: "a nested rule", path: "css.selectors.nesting", guard: never, offset: from });
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return;
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}
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let at = from;
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for (const declaration of body.split(";")) {
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const colon = declaration.indexOf(":");
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if (colon > 0) property(sheet, guards, declaration.slice(0, colon).trim().toLowerCase(), declaration.slice(colon + 1), at + declaration.search(/\S/));
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at += declaration.length + 1;
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}
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}
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function property(sheet: Sheet, guards: string[], name: string, value: string, offset: number): void {
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if (name.startsWith("-") && !name.startsWith("--")) return;
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const custom = name.startsWith("--");
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const known = custom || check(sheet, guards, { label: name, path: `css.properties.${name}`, guard: word(name), offset });
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for (const m of value.matchAll(/(?<![\w-])([a-z][\w-]*)\(/gi)) {
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const fn = m[1] ?? "";
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check(sheet, guards, { label: `${fn}()`, path: functionPath(name, fn), guard: new RegExp(`(?<![\\w-])${fn}\\(`, "i"), offset });
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}
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for (const m of value.replace(/#[\da-f]+/gi, "").matchAll(/(?<![\w.])\d*\.?\d+([a-z]+|%)/gi)) {
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const unit = (m[1] ?? "").toLowerCase();
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check(sheet, guards, { label: unit, path: unitPath(unit), guard: new RegExp(`\\d${unit}(?![\\w-])`, "i"), offset });
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}
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if (custom || !known || name === "font-family") return;
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for (const m of value.matchAll(/(?<![\w-])([a-z][\w-]*)(?![\w(-])/gi)) {
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const path = `css.properties.${name}.${(m[1] ?? "").toLowerCase()}`;
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if (entry(path)) check(sheet, guards, { label: `${name}: ${m[1]}`, path, guard: word(m[1] ?? ""), offset });
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}
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}
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const never = /(?!)/;
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const word = (name: string): RegExp => new RegExp(`(?<![\\w-])${name}(?![\\w-])`, "i");
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// A name two types share, like rect() in <shape> and <basic-shape>, passes where the floor has either.
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function functionPath(property: string, fn: string): string | undefined {
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const name = fn === "rgba" ? "rgb" : fn; // MDN files rgba() under rgb(), its alias
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const types = Object.keys(bcd.css.types ?? {}).map((type) => `css.types.${type}.${name}`);
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const paths = [`css.properties.${property}.${name}`, `css.types.${name}`, ...types].filter((path) => entry(path));
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return paths.find((path) => lacking(entry(path)?.support ?? {}).length === 0) ?? paths[0];
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}
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const VIEWPORT: Record<string, string> = { d: "dynamic", s: "small", l: "large" };
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const UNIT_TYPES: Record<string, string> = {
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px: "css.types.length",
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"%": "css.types.percentage",
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fr: "css.types.flex",
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s: "css.types.time",
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ms: "css.types.time",
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};
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function unitPath(unit: string): string | undefined {
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const viewport = /^([dsl])v(?:h|w|i|b|min|max)$/.exec(unit)?.[1];
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if (viewport) return `css.types.length.viewport_percentage_units_${VIEWPORT[viewport]}`;
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return UNIT_TYPES[unit] ?? ["length", "angle", "resolution"].map((type) => `css.types.${type}.${unit}`).find((path) => entry(path));
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}
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function entry(path: string | undefined): CompatStatement | undefined {
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if (!path) return undefined;
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let node: Identifier | undefined = { css: bcd.css };
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for (const key of path.split(".")) node = node && Object.hasOwn(node, key) ? node[key] : undefined;
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return node?.__compat;
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}
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// Reports the feature unless a guard names it or the floor has it; returns true when either holds.
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function check(sheet: Sheet, guards: string[], feature: Feature): boolean {
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if (guards.some((condition) => feature.guard.test(condition))) return true;
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const line = lineAt(sheet.css, feature.offset);
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const compat = entry(feature.path);
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if (!compat) {
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sheet.out.push(`line ${line}: ${feature.label} has no MDN compat entry`);
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return false;
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}
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const missing = lacking(compat.support);
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if (missing.length > 0) sheet.out.push(`line ${line}: ${feature.label} needs ${missing.join(", ")} (${feature.path})`);
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return missing.length === 0;
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}
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// Each floor engine without the feature, with the first later release that has it, as "safari 15.4".
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export function lacking(support: SupportBlock): string[] {
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return FLOOR.flatMap(([browser, floor]) => {
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const statements = [support[browser] ?? []].flat().filter((s) => !s.prefix && !s.alternative_name && !s.flags);
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const has = (s: SimpleSupportStatement): boolean => {
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const added = release(s.version_added);
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return added !== undefined && !newer(added, floor) && !(s.version_removed && !newer(s.version_removed, floor));
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};
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if (statements.some(has)) return [];
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const releases = statements.flatMap((s) => release(s.version_added) ?? []).filter((v) => newer(v, floor));
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releases.sort((x, y) => (newer(x, y) ? 1 : -1));
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return [`${browser} ${releases[0] ?? "(none yet)"}`];
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});
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}
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// A shipped release number; "≤79" counts as 79, "preview" and false as none.
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function release(version: string | false): string | undefined {
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return typeof version === "string" && /^≤?\d/.test(version) ? version.replace("≤", "") : undefined;
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}
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function newer(version: string, than: string): boolean {
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const [a, b] = [version, than].map((v) => v.split(".").map(Number));
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for (let i = 0; i < Math.max(a?.length ?? 0, b?.length ?? 0); i++) {
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if ((a?.[i] ?? 0) !== (b?.[i] ?? 0)) return (a?.[i] ?? 0) > (b?.[i] ?? 0);
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}
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return false;
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}
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