Fix invalid email field error

Instead of crashing with a cryptic message, instead we print an error
message.

Also, as a bonus, better testing instructions!

Fixes #3
Fixes #2

README.md

@@ -31,6 +31,35 @@ Configuration values are as follows:
 |`ldap_sync_interval_seconds`|Integer|Optional|Number of seconds to wait between each LDAP request. Defaults to `60`|
 |`ldap_sync_loop`|Boolean|Optional|Indicates whether or not syncing should be polled in a loop or done once. Defaults to `true`|
 
+## Testing
+
+All testing is manual right now. First step is to set up Bitwarden and the LDAP server.
+
+```bash
+docker-compose up -d bitwarden ldap ldap_admin
+```
+
+1. After that, open the admin portal on http://localhost:8001 and log in using the default account info:
+
+    Username: cn=admin,dc=example,dc=org
+    Password: admin
+
+From there you can set up your test group and users.
+
+2. Expand the `dc=example,dc=org` nav tree and select "Create new entry here"
+3. Select "Generic: Posix Group"
+4. Give it a name, eg. "Users" and then save and commit
+5. Select "Create child object"
+6. Select "Generic: User Account"
+7. Give the user a name and select a group ID number and save and commit
+8. Select "Add new attribute" and select "Email" and then add a test email address
+
+9. Run the ldap sync
+
+```bash
+docker-compose up ldap_sync
+```
+
 ## Future
 
 * Any kind of proper logging

docker-compose.yml

@@ -6,7 +6,8 @@ services:
       # dockerfile: Dockerfile.alpine
     volumes:
       - ./example.config.toml:/usr/src/bitwarden_rs_ldap/config.toml:ro
-      # - ./example.config.toml:/config.toml:ro
+    environment:
+      RUST_BACKTRACE: 1
     restart: always
 
   bitwarden:

src/config.rs

@@ -131,10 +131,9 @@ impl Config {
     }
 
     pub fn get_ldap_mail_field(&self) -> String {
-        let default = String::from("mail");
         match &self.ldap_mail_field {
             Some(mail_field) => mail_field.clone(),
-            None => default.clone(),
+            None => String::from("mail").clone(),
         }
     }
 

src/main.rs

@@ -114,7 +114,12 @@ fn invite_from_ldap(
             let mail_field = config.get_ldap_mail_field();
             let mut num_users = 0;
             for ldap_user in search_entries(config)? {
-                if let Some(user_email) = ldap_user.attrs[mail_field.as_str()].first() {
+                // Safely get first email from list of emails in field
+                if let Some(user_email) = ldap_user
+                    .attrs
+                    .get(mail_field.as_str())
+                    .and_then(|l| (l.first()))
+                {
                     if existing_users.contains(user_email) {
                         println!("User with email already exists: {}", user_email);
                     } else {
@@ -124,6 +129,8 @@ fn invite_from_ldap(
                         num_users = num_users + 1;
                         // println!("Invite response: {:?}", response);
                     }
+                } else {
+                    println!("Warning: Email field, {:?}, not found on user", mail_field);
                 }
             }