extension.js

// The module 'vscode' contains the VS Code extensibility API
// Import the module and reference it with the alias vscode in your code below
const vscode = require("vscode");
const cp = require("child_process");
const fs = require("fs");

// this method is called when your extension is activated
// your extension is activated the very first time the command is executed
function activate(context) {
    // Use the console to output diagnostic information (console.log) and errors (console.error)
    // This line of code will only be executed once when your extension is activated
    console.log('"refine-c" is now active!');

    // The command has been defined in the package.json file
    // Now provide the implementation of the command with  registerCommand
    // The commandId parameter must match the command field in package.json
    let disposable = vscode.commands.registerCommand(
        "refine-c.refine",
        function() {
            // The code you place here will be executed every time your command is executed
            const currentWorkingFile = vscode.window.activeTextEditor.document;
            const enableLanguage = vscode.workspace
                .getConfiguration("refine-c")
                .get("enableLanguages");
            // console.log(enableLanguage);

            // Check refineLanguage
            let refineLang = vscode.workspace
                .getConfiguration("refine-c")
                .get("refineLanguage");
            const supportLang = [
                "none",
                "c",
                "c-header",
                "c++",
                "c++-header",
                "objective-c",
                "objective-c-header",
                "objective-c++",
                "objective-c++-header"
            ];
            if (supportLang.indexOf(refineLang) === -1) refineLang = "none";

            // Check for documentLanguage
            if (
                currentWorkingFile.languageId === "c" ||
                currentWorkingFile.languageId === "cpp" ||
                currentWorkingFile.languageId === "objective-c" ||
                currentWorkingFile.languageId === "objective-cpp" ||
                enableLanguage.indexOf(currentWorkingFile.languageId) !== -1
            ) {
                if (!currentWorkingFile) {
                    vscode.window.showInformationMessage("No file was chosen!");
                    return;
                }
                if (
                    currentWorkingFile.isUntitled ||
                    currentWorkingFile.isDirty
                ) {
                    vscode.window.showWarningMessage(
                        "Your file was not saved!"
                    );
                    return;
                }
                const fileName = currentWorkingFile.fileName;

                // Executing
                const process = cp.spawn("gcc", [
                    "-E",
                    "-CC",
                    "-P",
                    "-undef",
                    "-dI",
                    "-nostdinc",
                    "-x",
                    refineLang,
                    fileName
                ]);

                // process.stderr.on("data", data => {
                //     console.log(`stderr: ${data}`);
                // });

                process.stdout.on("data", stdout => {
                    fs.writeFile(fileName, stdout, error => {
                        if (error)
                            vscode.window.showErrorMessage(error.message);
                        else {
                            // Display a message box to the user
                            vscode.window.showInformationMessage(
                                "Your code has been refined!"
                            );
                        }
                    });
                });
            } else
                vscode.window.showWarningMessage("Language is not supported!");
        }
    );

    context.subscriptions.push(disposable);
}
exports.activate = activate;

// this method is called when your extension is deactivated
function deactivate() {}
exports.deactivate = deactivate;