Catch multiple instances

Co-authored-by: John Wesley Walker III <81404201+jww3@users.noreply.github.com>

docs/commands.md

@@ -50,7 +50,9 @@ function setSecret(secret: string): void {}
 
 Now, future logs containing BAR will be masked. E.g. running `echo "Hello FOO BAR World"` will now print `Hello FOO **** World`.
 
-**WARNING** The add-mask and setSecret  commands only support single line secrets. To register a multiline secrets you must register each line individually otherwise it will not be masked.
+**WARNING** The add-mask command only supports single-line secrets. To register
+a multi-line secret, the recommended practice is to register each line individually. Otherwise, it will
+not be masked. `@actions/core >= 1.11.0` `setSecret` will perform this automatically.
 
 **WARNING** Do **not** mask short values if you can avoid it, it could render your output unreadable (and future steps' output as well).
 For example, if you mask the letter `l`, running `echo "Hello FOO BAR World"` will now print `He*********o FOO BAR Wor****d`

packages/core/__tests__/core.test.ts

@@ -164,6 +164,15 @@ describe('@actions/core', () => {
     assertWriteCalls([`::add-mask::secret val${os.EOL}`])
   })
 
+  it('setSecret splits multi line secrets into multiple commands', () => {
+    core.setSecret('first\nsecond\r\nthird')
+    assertWriteCalls([
+      `::add-mask::first${os.EOL}`,
+      `::add-mask::second${os.EOL}`,
+      `::add-mask::third${os.EOL}`
+    ])
+  })
+
   it('prependPath produces the correct commands and sets the env', () => {
     const command = 'PATH'
     createFileCommandFile(command)

packages/core/src/core.ts

@@ -97,7 +97,11 @@ export function exportVariable(name: string, val: any): void {
  * @param secret value of the secret
  */
 export function setSecret(secret: string): void {
-  issueCommand('add-mask', {}, secret)
+  for (const part of secret.split(/[\r\n]+/)) {
+    if (part) {
+      issueCommand('add-mask', {}, part)
+    }
+  }
 }
 
 /**