public static List<SecretSource> all() {
        return new ArrayList<>(Jenkins.get().getExtensionList(SecretSource.class));
    }
Reveal the plaintext value of a secret.

@param secret the variable reference to reveal

@return the secret's value, or Optional.empty() if a recoverable error occurred. (An empty Optional will allow CasC to continue processing the resolver chain.)
<p>Recoverable errors include:</p>
<ul>
<li>the secret was not found in the backing store</li>
</ul>

@throws IOException if an unrecoverable error occurred. (The exception will stop CasC processing the resolver chain.)
<p>Unrecoverable errors include:</p>
<ul>
<li>all attempts to contact the backing store have failed (including any applicable retry strategies)</li>
<li>authentication or authorization with the backing store failed</li>
<li>the secret's value was not convertible to a String</li>
</ul>
plugin/src/main/java/io/jenkins/plugins/casc/SecretSource.java