Remove unused variables from gulp tslint

RemoveUnusedVariablesGulpTslint.js

// Folder prefix for file names if running from a different path than gulp 
const fileNamePrefix = "";

// Relies on an "input.txt" to exist in the same directory
// That "input.txt" should be a listing of just the tslint failures
const inputFileName = "input.txt";

const fs = require("fs");

const lines = fs
    .readFileSync(inputFileName)
    .toString()
    .split("\n")
    .map(line => line.trim());

const errorLines = lines
    .filter(line => line.indexOf(": unused variable: ") !== -1)
    // Filter out gulp tslint summary messages
    .filter(line => line.indexOf("Failed to lint:") === -1);

const errorsInfo = errorLines
    // Remove any preceding '>', just in case
    .map(line => line.substring(line.indexOf(">") + 1))
    .map(originalErrorLine => {
        const parenthesisIndex = originalErrorLine.indexOf(") ") + 2;
        const bracketIndex = originalErrorLine.indexOf("[", parenthesisIndex);
        const fileName = fileNamePrefix + originalErrorLine.substring(parenthesisIndex, bracketIndex);
        const commaIndex = originalErrorLine.indexOf(",", bracketIndex);
        const lineNumber = parseInt(originalErrorLine.substring(bracketIndex + 1, commaIndex)) - 1;
        
        return { fileName, lineNumber, originalErrorLine };
    })
    .reverse();

const errorFileNames = errorsInfo.map(errorInfo => errorInfo.fileName);

errorsInfo.forEach(errorInfo => {
    const fileContents = fs.readFileSync(errorInfo.fileName).toString();
    const fileLines = fileContents.split("\r\n");

    const changedLinesBefore = fileLines
        .slice(0, errorInfo.lineNumber)

    var changedLinesAfter = fileLines
        .slice(errorInfo.lineNumber + 1);

    const changedLines = changedLinesBefore.concat(changedLinesAfter);

    fs.writeFileSync(errorInfo.fileName, changedLines.join("\r\n"));
});