ruby: add bindings for `notmuch_database_get_all_tags`

The Ruby bindings were missing a way to get all the tags of the
database. Now you should be able to access this with the public
instance method `all_tags` of your database object.

Example of use:
    notmuchdb = Notmuch::Database.new path, { :create => false,
    	:mode => Notmuch::MODE_READ_ONLY }

    my_tags = notmuchdb.all_tags

    my_tags.each { |tag|
      print tag
    }

    my_tags.destroy!

Amended by db: improve error reporting, add test

5 files changed, 52 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index c945c245..90e233bf 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,11 @@
+Notmuch 0.23 (UNRELEASED)
+=========================
+
+Ruby Bindings
+-------------
+
+Add support for `notmuch_database_get_all_tags`
+
 Notmuch 0.22 (2016-04-26)
 =========================
 
diff --git a/bindings/ruby/database.c b/bindings/ruby/database.c
index c03d7011..6deda575 100644
--- a/bindings/ruby/database.c
+++ b/bindings/ruby/database.c
@@ -375,6 +375,30 @@ notmuch_rb_database_find_message_by_filename (VALUE self, VALUE pathv)
 }
 
 /*
+ * call-seq: DB.get_all_tags() => TAGS
+ *
+ * Returns a list of all tags found in the database.
+ */
+VALUE
+notmuch_rb_database_get_all_tags (VALUE self)
+{
+    notmuch_database_t *db;
+    notmuch_tags_t *tags;
+
+    Data_Get_Notmuch_Database (self, db);
+
+    tags = notmuch_database_get_all_tags (db);
+    if (!tags) {
+	const char *msg = notmuch_database_status_string (db);
+	if (!msg)
+	    msg = "Unknown notmuch error";
+
+	rb_raise (notmuch_rb_eBaseError, "%s", msg);
+    }
+    return Data_Wrap_Struct (notmuch_rb_cTags, NULL, NULL, tags);
+}
+
+/*
  * call-seq: DB.query(query) => QUERY
  *
  * Retrieve a query object for the query string 'query'
diff --git a/bindings/ruby/defs.h b/bindings/ruby/defs.h
index f4901a04..167250e4 100644
--- a/bindings/ruby/defs.h
+++ b/bindings/ruby/defs.h
@@ -178,6 +178,9 @@ VALUE
 notmuch_rb_database_find_message_by_filename (VALUE self, VALUE pathv);
 
 VALUE
+notmuch_rb_database_get_all_tags (VALUE self);
+
+VALUE
 notmuch_rb_database_query_create (VALUE self, VALUE qstrv);
 
 /* directory.c */
diff --git a/bindings/ruby/init.c b/bindings/ruby/init.c
index ab3f22df..865d6bf6 100644
--- a/bindings/ruby/init.c
+++ b/bindings/ruby/init.c
@@ -229,6 +229,7 @@ Init_notmuch (void)
 		      notmuch_rb_database_find_message, 1); /* in database.c */
     rb_define_method (notmuch_rb_cDatabase, "find_message_by_filename",
 		      notmuch_rb_database_find_message_by_filename, 1); /* in database.c */
+    rb_define_method (notmuch_rb_cDatabase, "all_tags", notmuch_rb_database_get_all_tags, 0); /* in database.c */
     rb_define_method (notmuch_rb_cDatabase, "query", notmuch_rb_database_query_create, 1); /* in database.c */
 
     /*
diff --git a/test/T395-ruby.sh b/test/T395-ruby.sh
index d5cade8f..20e06917 100755
--- a/test/T395-ruby.sh
+++ b/test/T395-ruby.sh
@@ -83,4 +83,20 @@ EOF
 notmuch count --output=threads tag:inbox > EXPECTED
 test_expect_equal_file OUTPUT EXPECTED
 
+test_begin_subtest "get all tags"
+test_ruby <<"EOF"
+require 'notmuch'
+$maildir = ENV['MAIL_DIR']
+if not $maildir then
+  abort('environment variable MAIL_DIR must be set')
+end
+@db = Notmuch::Database.new($maildir)
+@t = @db.all_tags()
+for tag in @t do
+   print tag,"\n"
+end
+EOF
+notmuch search --output=tags '*' > EXPECTED
+test_expect_equal_file OUTPUT EXPECTED
+
 test_done