6-restructBlock.cjs•10.9 kB
'use strict';
const cssTree = require('css-tree');
let fingerprintId = 1;
const dontRestructure = new Set([
'src' // https://github.com/afelix/csso/issues/50
]);
const DONT_MIX_VALUE = {
// https://developer.mozilla.org/en-US/docs/Web/CSS/display#Browser_compatibility
'display': /table|ruby|flex|-(flex)?box$|grid|contents|run-in/i,
// https://developer.mozilla.org/en/docs/Web/CSS/text-align
'text-align': /^(start|end|match-parent|justify-all)$/i
};
const SAFE_VALUES = {
cursor: [
'auto', 'crosshair', 'default', 'move', 'text', 'wait', 'help',
'n-resize', 'e-resize', 's-resize', 'w-resize',
'ne-resize', 'nw-resize', 'se-resize', 'sw-resize',
'pointer', 'progress', 'not-allowed', 'no-drop', 'vertical-text', 'all-scroll',
'col-resize', 'row-resize'
],
overflow: [
'hidden', 'visible', 'scroll', 'auto'
],
position: [
'static', 'relative', 'absolute', 'fixed'
]
};
const NEEDLESS_TABLE = {
'border-width': ['border'],
'border-style': ['border'],
'border-color': ['border'],
'border-top': ['border'],
'border-right': ['border'],
'border-bottom': ['border'],
'border-left': ['border'],
'border-top-width': ['border-top', 'border-width', 'border'],
'border-right-width': ['border-right', 'border-width', 'border'],
'border-bottom-width': ['border-bottom', 'border-width', 'border'],
'border-left-width': ['border-left', 'border-width', 'border'],
'border-top-style': ['border-top', 'border-style', 'border'],
'border-right-style': ['border-right', 'border-style', 'border'],
'border-bottom-style': ['border-bottom', 'border-style', 'border'],
'border-left-style': ['border-left', 'border-style', 'border'],
'border-top-color': ['border-top', 'border-color', 'border'],
'border-right-color': ['border-right', 'border-color', 'border'],
'border-bottom-color': ['border-bottom', 'border-color', 'border'],
'border-left-color': ['border-left', 'border-color', 'border'],
'margin-top': ['margin'],
'margin-right': ['margin'],
'margin-bottom': ['margin'],
'margin-left': ['margin'],
'padding-top': ['padding'],
'padding-right': ['padding'],
'padding-bottom': ['padding'],
'padding-left': ['padding'],
'font-style': ['font'],
'font-variant': ['font'],
'font-weight': ['font'],
'font-size': ['font'],
'font-family': ['font'],
'list-style-type': ['list-style'],
'list-style-position': ['list-style'],
'list-style-image': ['list-style']
};
function getPropertyFingerprint(propertyName, declaration, fingerprints) {
const realName = cssTree.property(propertyName).basename;
if (realName === 'background') {
return propertyName + ':' + cssTree.generate(declaration.value);
}
const declarationId = declaration.id;
let fingerprint = fingerprints[declarationId];
if (!fingerprint) {
switch (declaration.value.type) {
case 'Value':
const special = {};
let vendorId = '';
let iehack = '';
let raw = false;
declaration.value.children.forEach(function walk(node) {
switch (node.type) {
case 'Value':
case 'Brackets':
case 'Parentheses':
node.children.forEach(walk);
break;
case 'Raw':
raw = true;
break;
case 'Identifier': {
const { name } = node;
if (!vendorId) {
vendorId = cssTree.keyword(name).vendor;
}
if (/\\[09]/.test(name)) {
iehack = RegExp.lastMatch;
}
if (SAFE_VALUES.hasOwnProperty(realName)) {
if (SAFE_VALUES[realName].indexOf(name) === -1) {
special[name] = true;
}
} else if (DONT_MIX_VALUE.hasOwnProperty(realName)) {
if (DONT_MIX_VALUE[realName].test(name)) {
special[name] = true;
}
}
break;
}
case 'Function': {
let { name } = node;
if (!vendorId) {
vendorId = cssTree.keyword(name).vendor;
}
if (name === 'rect') {
// there are 2 forms of rect:
// rect(<top>, <right>, <bottom>, <left>) - standart
// rect(<top> <right> <bottom> <left>) – backwards compatible syntax
// only the same form values can be merged
const hasComma = node.children.some((node) =>
node.type === 'Operator' && node.value === ','
);
if (!hasComma) {
name = 'rect-backward';
}
}
special[name + '()'] = true;
// check nested tokens too
node.children.forEach(walk);
break;
}
case 'Dimension': {
const { unit } = node;
if (/\\[09]/.test(unit)) {
iehack = RegExp.lastMatch;
}
switch (unit) {
// is not supported until IE11
case 'rem':
// v* units is too buggy across browsers and better
// don't merge values with those units
case 'vw':
case 'vh':
case 'vmin':
case 'vmax':
case 'vm': // IE9 supporting "vm" instead of "vmin".
special[unit] = true;
break;
}
break;
}
}
});
fingerprint = raw
? '!' + fingerprintId++
: '!' + Object.keys(special).sort() + '|' + iehack + vendorId;
break;
case 'Raw':
fingerprint = '!' + declaration.value.value;
break;
default:
fingerprint = cssTree.generate(declaration.value);
}
fingerprints[declarationId] = fingerprint;
}
return propertyName + fingerprint;
}
function needless(props, declaration, fingerprints) {
const property = cssTree.property(declaration.property);
if (NEEDLESS_TABLE.hasOwnProperty(property.basename)) {
const table = NEEDLESS_TABLE[property.basename];
for (const entry of table) {
const ppre = getPropertyFingerprint(property.prefix + entry, declaration, fingerprints);
const prev = props.hasOwnProperty(ppre) ? props[ppre] : null;
if (prev && (!declaration.important || prev.item.data.important)) {
return prev;
}
}
}
}
function processRule(rule, item, list, props, fingerprints) {
const declarations = rule.block.children;
declarations.forEachRight(function(declaration, declarationItem) {
const { property } = declaration;
const fingerprint = getPropertyFingerprint(property, declaration, fingerprints);
const prev = props[fingerprint];
if (prev && !dontRestructure.has(property)) {
if (declaration.important && !prev.item.data.important) {
props[fingerprint] = {
block: declarations,
item: declarationItem
};
prev.block.remove(prev.item);
// TODO: use it when we can refer to several points in source
// declaration.loc = {
// primary: declaration.loc,
// merged: prev.item.data.loc
// };
} else {
declarations.remove(declarationItem);
// TODO: use it when we can refer to several points in source
// prev.item.data.loc = {
// primary: prev.item.data.loc,
// merged: declaration.loc
// };
}
} else {
const prev = needless(props, declaration, fingerprints);
if (prev) {
declarations.remove(declarationItem);
// TODO: use it when we can refer to several points in source
// prev.item.data.loc = {
// primary: prev.item.data.loc,
// merged: declaration.loc
// };
} else {
declaration.fingerprint = fingerprint;
props[fingerprint] = {
block: declarations,
item: declarationItem
};
}
}
});
if (declarations.isEmpty) {
list.remove(item);
}
}
function restructBlock(ast) {
const stylesheetMap = {};
const fingerprints = Object.create(null);
cssTree.walk(ast, {
visit: 'Rule',
reverse: true,
enter(node, item, list) {
const stylesheet = this.block || this.stylesheet;
const ruleId = (node.pseudoSignature || '') + '|' + node.prelude.children.first.id;
let ruleMap;
let props;
if (!stylesheetMap.hasOwnProperty(stylesheet.id)) {
ruleMap = {};
stylesheetMap[stylesheet.id] = ruleMap;
} else {
ruleMap = stylesheetMap[stylesheet.id];
}
if (ruleMap.hasOwnProperty(ruleId)) {
props = ruleMap[ruleId];
} else {
props = {};
ruleMap[ruleId] = props;
}
processRule.call(this, node, item, list, props, fingerprints);
}
});
}
module.exports = restructBlock;