P4TB-394: Avoid a second passphrase prompt after the prompt is cancelled.

addon/content/pEpForThunderbird.js

@@ -47,6 +47,9 @@ class pEpForThunderbird extends pEp {
     // Cheap caching scheme follows.
     this.currentHeaderMessage = null;
     this.currentMimePartMessage = null;
+    this.currentHeaderMessageNoPassphrase = null;
+    this.currentMimePartMessageNoPassphrase = null;
+    this.timeNoPassphrase = null;
     this.currentHeaderMimeMessage = null;
     this.currentMimePartMimeMessage = null;
     this.currentMessage = null;      // Decrypted pEp message.
@@ -753,6 +756,15 @@ class pEpForThunderbird extends pEp {
       return this.currentMessage;
     }
 
+    if (msgHdr == this.currentHeaderMessageNoPassphrase &&
+        mimePart == this.currentMimePartMessageNoPassphrase &&
+        Date.now() - this.timeNoPassphrase < 1000) {
+      // We've come here a second time in less than a second for the same message.
+      // Likely a click onto the message first triggered the PGP Proxy to request it
+      // and then `updateMessagePanel()` requested it again.
+      throw new Error("Necessary passphrase not supplied");
+    }
+
     this.log.info(`getDecryptedMessage will ${mimeText ? "NOT " : ""}call readMailFromURI()`);
     if (!mimeText) {
       mimeText = this.readMailFromURI(msgUri);
@@ -778,8 +790,17 @@ class pEpForThunderbird extends pEp {
     message.bcc = message.bcc && message.bcc.map((addr) => makeIdentity(addr));
 
     // Decrypt.
-    let decryptedPromise = this.cache_decrypt_message(message);
-    this.currentMessage = this.synchronise(decryptedPromise);
+    try {
+      let decryptedPromise = this.cache_decrypt_message(message);
+      this.currentMessage = this.synchronise(decryptedPromise);
+    } catch (ex) {
+      if (ex.message == "Necessary passphrase not supplied") {
+        this.currentHeaderMessageNoPassphrase = (msgHdr == "no-header") ? null : msgHdr;
+        this.currentMimePartMessageNoPassphrase = mimePart;
+        this.timeNoPassphrase = Date.now();
+      }
+      throw ex;
+    }
 
     // Copy some headers from the original to the new message.
     // Starting with https://pep-security.lu/dev/repos/pEp_for_Thunderbird/rev/d3c752abce8c
@@ -819,6 +840,8 @@ class pEpForThunderbird extends pEp {
 
     this.currentHeaderMessage = (msgHdr == "no-header") ? null : msgHdr;
     this.currentMimePartMessage = mimePart;
+    this.currentHeaderMessageNoPassphrase = null;
+    this.currentMimePartMessageNoPassphrase = null;
     return this.currentMessage;
   }