Bug 1621116: Make the version and build ID of the previous instance of Firefox to use the current profile available. r=froydnj

We cache this information in compatibility.ini so we can just expose it on
nsIXULRuntime.

Differential Revision: https://phabricator.services.mozilla.com/D66112

--HG--
extra : moz-landing-system : lando

toolkit/xre/nsAppRunner.cpp

@@ -690,6 +690,39 @@ nsXULAppInfo::GetRemoteType(nsAString& aRemoteType) {
   return NS_OK;
 }
 
+static nsCString gLastAppVersion;
+static nsCString gLastAppBuildID;
+
+NS_IMETHODIMP
+nsXULAppInfo::GetLastAppVersion(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (!gLastAppVersion.IsVoid() && gLastAppVersion.IsEmpty()) {
+    NS_WARNING("Attempt to retrieve lastAppVersion before it has been set.");
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  aResult.Assign(gLastAppVersion);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetLastAppBuildID(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (!gLastAppBuildID.IsVoid() && gLastAppBuildID.IsEmpty()) {
+    NS_WARNING("Attempt to retrieve lastAppBuildID before it has been set.");
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  aResult.Assign(gLastAppBuildID);
+  return NS_OK;
+}
+
 static bool gBrowserTabsRemoteAutostart = false;
 static uint64_t gBrowserTabsRemoteStatus = 0;
 static bool gBrowserTabsRemoteAutostartInitialized = false;
@@ -2450,8 +2483,14 @@ static int32_t CompareBuildIDs(nsACString& oldID, nsACString& newID) {
  */
 int32_t CompareCompatVersions(const nsACString& aOldCompatVersion,
                               const nsACString& aNewCompatVersion) {
+  NS_ASSERTION(gLastAppVersion.IsVoid() && gLastAppBuildID.IsVoid(),
+               "lastAppVersion and lastAppBuildID should be void.");
+
   // Quick path for the common case.
   if (aOldCompatVersion.Equals(aNewCompatVersion)) {
+    gLastAppVersion.Assign(gAppData->version);
+    gLastAppBuildID.Assign(gAppData->buildID);
+
     return 0;
   }
 
@@ -2465,10 +2504,8 @@ int32_t CompareCompatVersions(const nsACString& aOldCompatVersion,
     return -1;
   }
 
-  nsCString oldVersion;
-  nsCString oldAppBuildID;
   nsCString oldPlatformBuildID;
-  ExtractCompatVersionInfo(aOldCompatVersion, oldVersion, oldAppBuildID,
+  ExtractCompatVersionInfo(aOldCompatVersion, gLastAppVersion, gLastAppBuildID,
                            oldPlatformBuildID);
 
   nsCString newVersion;
@@ -2478,13 +2515,13 @@ int32_t CompareCompatVersions(const nsACString& aOldCompatVersion,
                            newPlatformBuildID);
 
   // In most cases the app version will differ and this is an easy check.
-  int32_t result = CompareVersions(oldVersion.get(), newVersion.get());
+  int32_t result = CompareVersions(gLastAppVersion.get(), newVersion.get());
   if (result != 0) {
     return result;
   }
 
   // Fall back to build ID comparison.
-  result = CompareBuildIDs(oldAppBuildID, newAppBuildID);
+  result = CompareBuildIDs(gLastAppBuildID, newAppBuildID);
   if (result != 0) {
     return result;
   }
@@ -2508,6 +2545,8 @@ static bool CheckCompatibility(nsIFile* aProfileDir, const nsCString& aVersion,
                                nsCString& aLastVersion) {
   *aCachesOK = false;
   *aIsDowngrade = false;
+  gLastAppVersion.SetIsVoid(true);
+  gLastAppBuildID.SetIsVoid(true);
 
   nsCOMPtr<nsIFile> file;
   aProfileDir->Clone(getter_AddRefs(file));

xpcom/system/nsIXULRuntime.idl

@@ -212,4 +212,20 @@ interface nsIXULRuntime : nsISupports
    * |mozilla::LauncherRegistryInfo::EnabledState| values.
    */
   readonly attribute uint32_t launcherProcessState;
+
+  /**
+   * Returns the last application version that used the current profile or null
+   * if the last version could not be found (compatibility.ini was either
+   * missing or invalid). Throws NS_ERROR_UNAVAILABLE if called from a content
+   * process.
+   */
+  readonly attribute ACString lastAppVersion;
+
+  /**
+   * Returns the last application build ID that used the current profile or null
+   * if the last build ID could not be found (compatibility.ini was either
+   * missing or invalid). Throws NS_ERROR_UNAVAILABLE if called from a content
+   * process.
+   */
+  readonly attribute ACString lastAppBuildID;
 };