Refactor to not use the helper script (#6)

Choose vcvarsall.bat within JS code, call CMD directly with a command instead of writing a temporary file.

index.js

@@ -1,8 +1,6 @@
 const core = require('@actions/core')
-const execFile = require('util').promisify(require('child_process').execFile)
-const fs = require('fs').promises
-const os = require('os')
-const path = require('path')
+const exec = require('util').promisify(require('child_process').exec)
+const fs = require('fs')
 const process = require('process')
 
 const EDITIONS = ['Enterprise', 'Professional', 'Community']
@@ -20,32 +18,28 @@ const InterestingVariables = [
     /^WindowsSDK/i,
 ]
 
+function findVcvarsall() {
+    const programFiles = process.env['ProgramFiles(x86)']
+    // Given the order of each list it should check
+    // for the more recent versions first and the
+    // highest grade edition first.
+    for (const ver of VERSIONS) {
+        for (const ed of EDITIONS) {
+            const path = `${programFiles}\\Microsoft Visual Studio\\${ver}\\${ed}\\VC\\Auxiliary\\Build\\vcvarsall.bat`
+            if (fs.existsSync(path)) {
+                return path
+            }
+        }
+    }
+    throw new Error('Microsoft Visual Studio not found')
+}
+
 async function main() {
     if (process.platform != 'win32') {
         core.info('This is not a Windows virtual environment, bye!')
         return
     }
 
-    // this should generate an array like
-    // [
-    //     ['P2017', 'path\to\2017\Professional...'],
-    //     ['C2017', 'path\to\2017\Entreprise...'],
-    //     etc...
-    // [
-    // Given the order of each list it should check
-    // for the more recent versions first and the
-    // highest grade edition first.
-    var search_map = []
-
-    VERSIONS.forEach(ver => {
-        EDITIONS.forEach(ed => {
-            let label = ed.charAt(0) + ver
-            let path = `%ProgramFiles(x86)%\\Microsoft Visual Studio\\${ver}\\${ed}\\VC\\Auxiliary\\Build\\vcvarsall.bat`
-
-            search_map.push([label, path])
-        })
-    })
-
     const arch    = core.getInput('arch')
     const sdk     = core.getInput('sdk')
     const toolset = core.getInput('toolset')
@@ -53,10 +47,7 @@ async function main() {
     const spectre = core.getInput('spectre')
 
     // Due to the way Microsoft Visual C++ is configured, we have to resort to the following hack:
-    // write a helper batch file which calls the configuration batch file and then outputs the
-    // configured environment variables, which we then pass to GitHub Actions.
-
-    const helper = path.join(os.homedir(), 'msvc-dev-cmd.bat')
+    // Call the configuration batch file and then output *all* the environment variables.
 
     var args = [arch]
     if (uwp == 'true') {
@@ -71,46 +62,11 @@ async function main() {
     if (spectre == 'true') {
         args.push('-vcvars_spectre_libs=spectre')
     }
-    core.debug(`Arguments: ${args.join(' ')}`)
 
-    var script = '';
-
-    search_map.forEach(pair => {
-        script += `@IF EXIST "${pair[1]}" GOTO :${pair[0]}\n`
-    })
-
-    script += `@ECHO "Microsoft Visual Studio not found"\n
-               @EXIT 1\n`
-
-    search_map.forEach(pair => {
-        script += `:${pair[0]}\n
-                   @CALL "${pair[1]}" ${args.join(' ')}\n
-                   @GOTO ENV\n`
-    })
-
-    script += `:ENV\n
-               @IF ERRORLEVEL 1 EXIT\n
-               @SET`
-
-    core.debug(script)
-
-    core.debug(`Writing helper file: ${helper}`)
-    await fs.writeFile(helper, script)
-
-    var environment
-    try {
-        core.debug('Executing helper')
-        const { stdout } = await execFile('cmd.exe', ['/q', '/c', helper])
-        environment = stdout.split('\r\n')
-    }
-    catch (error) {
-        core.debug(`Helper failed: ${error.message}`)
-        throw error
-    }
-    finally {
-        core.debug('Removing helper')
-        await fs.unlink(helper)
-    }
+    const command = `"${findVcvarsall()}" ${args.join(' ')} && set`
+    core.debug(`Running: ${command}`)
+    const { stdout } = await exec(command, {shell: "cmd"})
+    const environment = stdout.split('\r\n')
 
     for (let string of environment) {
         const [name, value] = string.split('=')