openpgp: Add a policy object.

  - Change all functions that need to evaluate the validity of a
    signature (either directly or indirectly to take a policy object.

  - Use the policy object to allow the user to place additional
    constraints on a signature's validity.

  - This addresses the first half of #274 (it introduces the policy
    object, but does not yet implement any policy).

1 files changed, 5 insertions, 2 deletions

diff --git a/examples/guide-exploring-openpgp.rs b/examples/guide-exploring-openpgp.rs
index e70c6361..05a777e4 100644
--- a/examples/guide-exploring-openpgp.rs
+++ b/examples/guide-exploring-openpgp.rs
@@ -2,8 +2,11 @@
 
 extern crate sequoia_openpgp as openpgp;
 use crate::openpgp::parse::Parse;
+use crate::openpgp::policy::StandardPolicy as P;
 
 fn main() {
+    let p = &P::new();
+
     let cert =
         "-----BEGIN PGP PUBLIC KEY BLOCK-----
 
@@ -52,7 +55,7 @@ fn main() {
     println!("Fingerprint: {}", cert.fingerprint());
 
     // List userids.
-    for (i, ca) in cert.userids().policy(None).enumerate() {
+    for (i, ca) in cert.userids().set_policy(p, None).enumerate() {
         println!("{}: UID: {}, {} self-signature(s), {} certification(s)",
                  i, ca.userid(),
                  ca.binding().self_signatures().len(),
@@ -60,7 +63,7 @@ fn main() {
     }
 
     // List subkeys.
-    for (i, ka) in cert.keys().policy(None).skip(1).enumerate() {
+    for (i, ka) in cert.keys().set_policy(p, None).skip(1).enumerate() {
         println!("{}: Fingerprint: {}, {} self-signature(s), {} certification(s)",
                  i, ka.key().fingerprint(),
                  ka.binding().self_signatures().len(),