@jspm/generator/lib/common/source-style.js

Package Import Map Generation Tool

import { isWindows } from './env.js';
export const defaultStyle = {
    tab: '  ',
    newline: isWindows ? '\r\n' : '\n',
    trailingNewline: isWindows ? '\r\n' : '\n',
    indent: '',
    quote: '"'
};
export function detectNewline(source) {
    let newLineMatch = source.match(/\r?\n|\r(?!\n)/);
    if (newLineMatch) return newLineMatch[0];
    return isWindows ? '\r\n' : '\n';
}
export function detectIndent(source, newline) {
    let indent = undefined;
    // best-effort tab detection
    // yes this is overkill, but it avoids possibly annoying edge cases
    let lines = source.split(newline);
    for (const line of lines){
        const curIndent = line.match(/^\s*[^\s]/);
        if (curIndent && (indent === undefined || curIndent.length < indent.length)) indent = curIndent[0].slice(0, -1);
    }
    indent = indent || '';
    lines = lines.map((line)=>line.slice(indent.length));
    let tabSpaces = lines.map((line)=>{
        var _line_match;
        return ((_line_match = line.match(/^[ \t]*/)) === null || _line_match === void 0 ? void 0 : _line_match[0]) || '';
    }) || [];
    let tabDifferenceFreqs = new Map();
    let lastLength = 0;
    tabSpaces.forEach((tabSpace)=>{
        let diff = Math.abs(tabSpace.length - lastLength);
        if (diff !== 0) tabDifferenceFreqs.set(diff, (tabDifferenceFreqs.get(diff) || 0) + 1);
        lastLength = tabSpace.length;
    });
    let bestTabLength = 0;
    for (const tabLength of tabDifferenceFreqs.keys()){
        if (!bestTabLength || tabDifferenceFreqs.get(tabLength) >= tabDifferenceFreqs.get(bestTabLength)) bestTabLength = tabLength;
    }
    // having determined the most common spacing difference length,
    // generate samples of this tab length from the end of each line space
    // the most common sample is then the tab string
    let tabSamples = new Map();
    tabSpaces.forEach((tabSpace)=>{
        let sample = tabSpace.substr(tabSpace.length - bestTabLength);
        tabSamples.set(sample, (tabSamples.get(sample) || 0) + 1);
    });
    let bestTabSample = '';
    for (const [sample, freq] of tabSamples){
        if (!bestTabSample || freq > tabSamples.get(bestTabSample)) bestTabSample = sample;
    }
    if (lines.length < 5 && lines.reduce((cnt, line)=>cnt + line.length, 0) < 100) bestTabSample = '  ';
    return {
        indent: indent || '',
        tab: bestTabSample
    };
}
export function detectStyle(source) {
    let style = Object.assign({}, defaultStyle);
    style.newline = detectNewline(source);
    let { indent, tab } = detectIndent(source, style.newline);
    style.indent = indent;
    style.tab = tab;
    let quoteMatch = source.match(/"|'/);
    if (quoteMatch) style.quote = quoteMatch[0];
    style.trailingNewline = source && source.match(new RegExp(style.newline + '$')) ? style.newline : '';
    return style;
}


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