Buck: Script to find out which rules should be tested based on what was changed

buck_targets_to_test.swift

import Foundation

func run(command: String, wait: Bool = true) -> String? {
    let task = Process()
    task.launchPath = "/bin/bash"
    task.arguments = ["-c", command]
    let pipe = Pipe()
    task.standardOutput = pipe
    task.launch()
    guard wait else {
        return ""
    }
    task.waitUntilExit()
    let data = pipe.fileHandleForReading.readDataToEndOfFile()
    return String(data: data, encoding: .utf8)
}

func runTargetsCommand() -> String? {
    return run(command: "./buck targets //... --show-target-hash")
}

func process(_ hashes: String) -> [String: String] {
    let rules = hashes.components(separatedBy: "\n")
    var dict = [String: String]()
    for rule in rules {
        let data = rule.components(separatedBy: " ")
        guard data.count == 2 else {
            continue
        }
        dict[data[0]] = data[1]
    }
    return dict
}

guard let newHashesResult = runTargetsCommand() else {
    fatalError("Failed to run buck targets command")
}

let newHashes = process(newHashesResult)

let oldHashesResult = run(command: "cat ./buck-out/cache/ifood_hashes.txt")

_ = run(command: "echo \"\(newHashesResult)\" > ./buck-out/cache/ifood_hashes.txt")

if oldHashesResult == "" {
    print("--all")
    exit(0)
}

let oldHashes = process(oldHashesResult!)

var targetsToBuild = [String]()

for (k, v) in newHashes where k.hasSuffix("Tests") {
    if oldHashes[k] != v {
        targetsToBuild.append(k)
    }
}

guard targetsToBuild.isEmpty == false else {
    // Return an empty test so we don't test anything
    print("//Libraries/Config/uUseless:UselessTests")
    exit(0)
}

let result = targetsToBuild.joined(separator: " ")
print(result)