Bug 1883846 - Rework/reinstate the GPGMELib debug output. r=kaie

Adding back debugging infor for GPGMELib.
This should not be using global console for debug info, if such info is warranted.
For error cases, we can log errors. To see debug only info, people should set `openpgp.loglevel` to `All`.

Differential Revision: https://phabricator.services.mozilla.com/D205423

--HG--
extra : rebase_source : f5399a64a9b0bfc18a60e89f9e1faf51f9ea0410
extra : amend_source : f87ec4551da5615a96bce2a0b23548b4a15077fa

mail/extensions/openpgp/content/modules/GPGMELib.sys.mjs

@@ -4,7 +4,12 @@
 
 import { ctypes } from "resource://gre/modules/ctypes.sys.mjs";
 
-var systemOS = Services.appinfo.OS.toLowerCase();
+var log = console.createInstance({
+  prefix: "openpgp",
+  maxLogLevel: "Warn",
+  maxLogLevelPref: "openpgp.loglevel",
+});
+
 var abi = ctypes.default_abi;
 
 // Default library paths to look for on macOS
@@ -36,25 +41,27 @@ function tryLoadGPGME(name, suffix) {
     } catch (e) {}
   }
 
-  if (!libgpgme && systemOS !== "winnt") {
+  if (!libgpgme && Services.appinfo.OS !== "WINNT") {
     // try specific additional directories
-
     for (const tryPath of ADDITIONAL_LIB_PATHS) {
       try {
         libgpgmePath = tryPath + "/" + filename;
         libgpgme = ctypes.open(libgpgmePath);
-
         if (libgpgme) {
           break;
         }
       } catch (e) {}
     }
   }
+
+  if (libgpgme) {
+    log.debug(`Loaded GPGME from ${libgpgmePath}`);
+  }
 }
 
 function loadExternalGPGMELib() {
   if (!libgpgme) {
-    if (systemOS === "winnt") {
+    if (Services.appinfo.OS === "WINNT") {
       tryLoadGPGME("libgpgme6-11", "");
 
       if (!libgpgme) {
@@ -217,13 +224,13 @@ function enableGPGMELibJS() {
     init() {
       // GPGME 1.9.0 released 2017-03-28 is the first version that
       // supports GPGME_DECRYPT_UNWRAP, requiring >= gpg 2.1.12
-      // const versionPtr = this.gpgme_check_version("1.9.0");
-      // const version = versionPtr.readString();
+      const version = this.gpgme_check_version("1.9.0").readString();
 
       const gpgExe = Services.prefs.getStringPref(
         "mail.openpgp.alternative_gpg_path"
       );
       if (!gpgExe) {
+        // Use the normal gpg executable.
         return true;
       }
 
@@ -233,6 +240,13 @@ function enableGPGMELibJS() {
         null
       );
       const success = extResult === this.GPG_ERR_NO_ERROR;
+      if (success) {
+        log.debug(`Using external OpenPGP engine; v${version}: ${gpgExe}`);
+      } else {
+        log.error(
+          `Could not use external OpenPGP engine; v${version}: ${gpgExe} - ${extResult}`
+        );
+      }
       return success;
     },