Add save-state and set-output file commands (#1178)

packages/core/src/file-command.ts

@@ -5,9 +5,10 @@
 
 import * as fs from 'fs'
 import * as os from 'os'
+import {v4 as uuidv4} from 'uuid'
 import {toCommandValue} from './utils'
 
-export function issueCommand(command: string, message: any): void {
+export function issueFileCommand(command: string, message: any): void {
   const filePath = process.env[`GITHUB_${command}`]
   if (!filePath) {
     throw new Error(
@@ -22,3 +23,25 @@ export function issueCommand(command: string, message: any): void {
     encoding: 'utf8'
   })
 }
+
+export function prepareKeyValueMessage(key: string, value: any): string {
+  const delimiter = `ghadelimiter_${uuidv4()}`
+  const convertedValue = toCommandValue(value)
+
+  // These should realistically never happen, but just in case someone finds a
+  // way to exploit uuid generation let's not allow keys or values that contain
+  // the delimiter.
+  if (key.includes(delimiter)) {
+    throw new Error(
+      `Unexpected input: name should not contain the delimiter "${delimiter}"`
+    )
+  }
+
+  if (convertedValue.includes(delimiter)) {
+    throw new Error(
+      `Unexpected input: value should not contain the delimiter "${delimiter}"`
+    )
+  }
+
+  return `${key}<<${delimiter}${os.EOL}${convertedValue}${os.EOL}${delimiter}`
+}