[geary/wip/composer-folks: 11/22] Replace Db.PrepareDelegate with a subclass virtual function hook

[Michael Gratton <mjog src gnome org>]

commit 5e13dd0abdc440763a8cb692542e510e1ca5cece
Author: Michael Gratton <mike vee net>
Date:   Tue Jun 11 07:21:35 2019 +1000

    Replace Db.PrepareDelegate with a subclass virtual function hook
    
    While slightly less flexible, it fits the Engine's needs and simplifies
    the DB API.

 src/engine/db/db-database.vala                   | 19 ++++++++++++-------
 src/engine/db/db-versioned-database.vala         |  7 +++----
 src/engine/db/db.vala                            | 14 --------------
 src/engine/imap-db/imap-db-database.vala         |  5 +++--
 test/engine/db/db-database-test.vala             | 14 +++++++-------
 test/engine/db/db-versioned-database-test.vala   |  2 +-
 test/engine/imap-db/imap-db-attachment-test.vala |  2 +-
 7 files changed, 27 insertions(+), 36 deletions(-)
---
diff --git a/src/engine/db/db-database.vala b/src/engine/db/db-database.vala
index 404aa4f0..e28180a4 100644
--- a/src/engine/db/db-database.vala
+++ b/src/engine/db/db-database.vala
@@ -65,7 +65,6 @@ public class Geary.Db.Database : Geary.Db.Context {
     private Connection? primary = null;
     private int outstanding_async_jobs = 0;
     private ThreadPool<TransactionAsyncJob>? thread_pool = null;
-    private unowned PrepareConnection? prepare_cb = null;
 
     /**
      * Constructs a new database that is persisted on disk.
@@ -104,14 +103,12 @@ public class Geary.Db.Database : Geary.Db.Context {
      * and Results.
      */
     public virtual async void open(DatabaseFlags flags,
-                                   PrepareConnection? prepare_cb,
                                    Cancellable? cancellable = null)
         throws Error {
         if (is_open)
             return;
 
         this.flags = flags;
-        this.prepare_cb = prepare_cb;
 
         if (this.file != null && (flags & DatabaseFlags.CREATE_DIRECTORY) != 0) {
             yield Geary.Files.make_directory_with_parents(this.file.get_parent());
@@ -235,9 +232,7 @@ public class Geary.Db.Database : Geary.Db.Context {
         }
 
         Connection cx = new Connection(this, sqlite_flags, cancellable);
-        if (prepare_cb != null)
-            prepare_cb(cx, is_primary);
-
+        prepare_connection(cx);
         return cx;
     }
 
@@ -365,6 +360,17 @@ public class Geary.Db.Database : Geary.Db.Context {
         this.thread_pool.add(new_job);
     }
 
+    /**
+     * Hook for subclasses to modify a new SQLite connection before use.
+     *
+     * This allows sub-classes to configure SQLite on a newly
+     * established connections before being used, such as setting
+     * pragmas, custom collation functions, and so on,
+     */
+    protected virtual void prepare_connection(Connection cx) throws GLib.Error {
+        // No-op by default;
+    }
+
     // This method must be thread-safe.
     private void on_async_job(owned TransactionAsyncJob job) {
         // *never* use primary connection for threaded operations
@@ -395,4 +401,3 @@ public class Geary.Db.Database : Geary.Db.Context {
         return this;
     }
 }
-
diff --git a/src/engine/db/db-versioned-database.vala b/src/engine/db/db-versioned-database.vala
index 24b2403c..ae9717a1 100644
--- a/src/engine/db/db-versioned-database.vala
+++ b/src/engine/db/db-versioned-database.vala
@@ -86,10 +86,9 @@ public class Geary.Db.VersionedDatabase : Geary.Db.Database {
      * the application.
      */
     public override async void open(DatabaseFlags flags,
-                                    PrepareConnection? prepare_cb,
-                                    Cancellable? cancellable = null)
-        throws Error {
-        yield base.open(flags, prepare_cb, cancellable);
+                                    GLib.Cancellable? cancellable = null)
+        throws GLib.Error {
+        yield base.open(flags, cancellable);
 
         // get Connection for upgrade activity
         Connection cx = yield open_connection(cancellable);
diff --git a/src/engine/db/db.vala b/src/engine/db/db.vala
index 9b4217df..ff362496 100644
--- a/src/engine/db/db.vala
+++ b/src/engine/db/db.vala
@@ -45,20 +45,6 @@ public enum ResetScope {
     CLEAR_BINDINGS
 }
 
-/*
- * PrepareConnection is called from Database when a Connection is created.  Database may pool
- * Connections, especially for asynchronous queries, so this is only called when a new
- * Connection is created and not when its reused.
- *
- * PrepareConnection may be used as an opportunity to modify or configure the Connection.
- * This callback is called prior to the Connection being used, either internally or handed off to
- * a caller for normal use.
- *
- * This callback may be called in the context of a background thread.
- */
-public delegate void PrepareConnection(Connection cx, bool is_primary)
-    throws GLib.Error;
-
 /**
  * See Connection.exec_transaction() for more information on how this delegate is used.
  */
diff --git a/src/engine/imap-db/imap-db-database.vala b/src/engine/imap-db/imap-db-database.vala
index 8c4e4761..f8a4b588 100644
--- a/src/engine/imap-db/imap-db-database.vala
+++ b/src/engine/imap-db/imap-db-database.vala
@@ -36,7 +36,7 @@ private class Geary.ImapDB.Database : Geary.Db.VersionedDatabase {
      */
     public new async void open(Db.DatabaseFlags flags, Cancellable? cancellable)
         throws Error {
-        yield base.open(flags, on_prepare_database_connection, cancellable);
+        yield base.open(flags, cancellable);
 
         // Tie user-supplied Cancellable to internal Cancellable, which is used when close() is
         // called
@@ -579,7 +579,8 @@ private class Geary.ImapDB.Database : Geary.Db.VersionedDatabase {
         stmt.exec();
     }
 
-    private void on_prepare_database_connection(Db.Connection cx) throws Error {
+    protected override void prepare_connection(Db.Connection cx)
+        throws GLib.Error {
         cx.set_busy_timeout_msec(Db.Connection.RECOMMENDED_BUSY_TIMEOUT_MSEC);
         cx.set_foreign_keys(true);
         cx.set_recursive_triggers(true);
diff --git a/test/engine/db/db-database-test.vala b/test/engine/db/db-database-test.vala
index 93502489..c8e746bd 100644
--- a/test/engine/db/db-database-test.vala
+++ b/test/engine/db/db-database-test.vala
@@ -22,7 +22,7 @@ class Geary.Db.DatabaseTest : TestCase {
     public void transient_open() throws Error {
         Database db = new Geary.Db.Database.transient();
         db.open.begin(
-            Geary.Db.DatabaseFlags.NONE, null, null,
+            Geary.Db.DatabaseFlags.NONE, null,
             (obj, ret) => { async_complete(ret); }
         );
         db.open.end(async_result());
@@ -40,7 +40,7 @@ class Geary.Db.DatabaseTest : TestCase {
 
         Database db = new Geary.Db.Database.persistent(tmp_file);
         db.open.begin(
-            Geary.Db.DatabaseFlags.NONE, null, null,
+            Geary.Db.DatabaseFlags.NONE, null,
             (obj, ret) => { async_complete(ret); }
         );
         db.open.end(async_result());
@@ -61,7 +61,7 @@ class Geary.Db.DatabaseTest : TestCase {
             tmp_dir.get_child("test.db")
         );
         db.open.begin(
-            Geary.Db.DatabaseFlags.CREATE_FILE, null, null,
+            Geary.Db.DatabaseFlags.CREATE_FILE, null,
             (obj, ret) => { async_complete(ret); }
         );
         db.open.end(async_result());
@@ -85,7 +85,7 @@ class Geary.Db.DatabaseTest : TestCase {
         db.open.begin(
             Geary.Db.DatabaseFlags.CREATE_DIRECTORY |
             Geary.Db.DatabaseFlags.CREATE_FILE,
-            null, null,
+            null,
             (obj, ret) => { async_complete(ret); }
         );
         db.open.end(async_result());
@@ -110,7 +110,7 @@ class Geary.Db.DatabaseTest : TestCase {
         db.open.begin(
             Geary.Db.DatabaseFlags.CREATE_DIRECTORY |
             Geary.Db.DatabaseFlags.CREATE_FILE,
-            null, null,
+            null,
             (obj, ret) => { async_complete(ret); }
         );
         db.open.end(async_result());
@@ -134,7 +134,7 @@ class Geary.Db.DatabaseTest : TestCase {
         db.open.begin(
             Geary.Db.DatabaseFlags.CREATE_FILE |
             Geary.Db.DatabaseFlags.CHECK_CORRUPTION,
-            null, null,
+            null,
             (obj, ret) => { async_complete(ret); }
         );
         db.open.end(async_result());
@@ -159,7 +159,7 @@ class Geary.Db.DatabaseTest : TestCase {
             Geary.Db.DatabaseFlags.CREATE_DIRECTORY |
             Geary.Db.DatabaseFlags.CREATE_FILE |
             Geary.Db.DatabaseFlags.CHECK_CORRUPTION,
-            null, null,
+            null,
             (obj, ret) => { async_complete(ret); }
         );
         db.open.end(async_result());
diff --git a/test/engine/db/db-versioned-database-test.vala b/test/engine/db/db-versioned-database-test.vala
index 6d52abc8..4e12962f 100644
--- a/test/engine/db/db-versioned-database-test.vala
+++ b/test/engine/db/db-versioned-database-test.vala
@@ -34,7 +34,7 @@ class Geary.Db.VersionedDatabaseTest : TestCase {
         );
 
         db.open.begin(
-            Geary.Db.DatabaseFlags.CREATE_FILE, null, null,
+            Geary.Db.DatabaseFlags.CREATE_FILE, null,
             (obj, ret) => { async_complete(ret); }
         );
         db.open.end(async_result());
diff --git a/test/engine/imap-db/imap-db-attachment-test.vala 
b/test/engine/imap-db/imap-db-attachment-test.vala
index 9456e6be..d24f2b8d 100644
--- a/test/engine/imap-db/imap-db-attachment-test.vala
+++ b/test/engine/imap-db/imap-db-attachment-test.vala
@@ -114,7 +114,7 @@ class Geary.ImapDB.AttachmentIoTest : TestCase {
 
         this.db = new Geary.Db.Database.transient();
         this.db.open.begin(
-            Geary.Db.DatabaseFlags.NONE, null, null,
+            Geary.Db.DatabaseFlags.NONE, null,
             (obj, res) => { async_complete(res); }
         );
         this.db.open.end(async_result());