Await Execution of a Subcommand and Parse its Output

Question

I'm attempting to run a command line tool and parse the output from stdout in order to do something useful with it in a VSCode extension. I'm attempting to create Flow objects (defined elsewhere in the code) and append them to this.flows; however, the function returns before this.flows is set.

    getChildren(element?: vscode.TreeItem): Thenable<Flow[]> | Flow[] | null {

        if (element === undefined) {
            exec(commandToRun, (error, stdout, stderr) => {
                let flowJson = JSON.parse(stdout); // output is expected in json format
                for (let i =0; i < jsonString.length; ++i) {
                    let f = new Flow(jsonString[i][name], flowJson[i]['description'], vscode.TreeItemCollapsibleState.None);
                    this.flows.push(f);
                }
            }
        }
        return new Promise<Flow[]>(resolve => resolve(this.flows));
    }

I believe it need to make use of await or then, but not sure how to incorporate them to achieve the desired result.

Any help is greatly appreciated, cheers!

Answer 1

It looks like you're using the async version of exec.

Instead, you can use execSync and avoid redundant async-awaits. For example:

let stdout = execSync(commandToRun)
let flowJson = JSON.parse(stdout); // output is expected in json format
for (let i =0; i < jsonString.length; ++i) {
    let f = new Flow(jsonString[i][name], flowJson[i]['description'], vscode.TreeItemCollapsibleState.None);
    this.flows.push(f);
}