Support :connect_opts_proc Database option for late binding options

Some modern authentication schemes automatically rotate usernames
and/or passwords on a regular basis without user involvement or
control.  Attempt to support this type of authentication case
with this option, so you can do something like:

  Sequel.connect('postgres://user@host/database',
    connect_opts_proc: lambda do |h|
      h[:password] = SomeAuthLibrary.get_current_password(h[:user])
    end)

The way this is implemented, the :connect_opts_proc is always
called before a new connection is made, so directly before the
connection is made, it will get the current password for
the account.

Note that for the jdbc adapter, because it generally works directly
on JDBC URIs, the :connect_opts_proc should probably set the :uri
key in the hash appropriately.

CHANGELOG

@@ -1,3 +1,7 @@
+=== master
+
+* Support :connect_opts_proc Database option for late binding options (jeremyevans) (#2164)
+
 === 5.81.0 (2024-06-01)
 
 * Fix ignored block warnings in a couple plugin apply methods on Ruby 3.4 (jeremyevans)

doc/opening_databases.rdoc

@@ -79,6 +79,9 @@ These options are shared by all adapters unless otherwise noted.
                or string with extensions separated by columns.  These extensions are loaded after
                connections are made by the :preconnect option.
 :cache_schema :: Whether schema should be cached for this database (true by default)
+:connect_opts_proc :: Callable object for modifying options hash used when connecting, designed for
+                      cases where the option values (e.g. password) are automatically rotated on
+                      a regular basis without involvement from the application using Sequel.
 :default_string_column_size :: The default size for string columns (255 by default)
 :host :: The hostname of the database server to which to connect
 :keep_reference :: Whether to keep a reference to the database in Sequel::DATABASES (true by default)

lib/sequel/database/connecting.rb

@@ -335,6 +335,11 @@ def server_opts(server)
       else
         @opts.dup
       end
+
+      if pr = opts[:connect_opts_proc]
+        pr.call(opts)
+      end
+
       opts.delete(:servers)
       opts
     end

lib/sequel/database/misc.rb

@@ -108,6 +108,9 @@ def self.uri_to_options(uri)
     # :cache_schema :: Whether schema should be cached for this Database instance
     # :check_string_typecast_bytesize :: Whether to check the bytesize of strings before typecasting.
     # :connect_sqls :: An array of sql strings to execute on each new connection, after :after_connect runs.
+    # :connect_opts_proc :: Callable object for modifying options hash used when connecting, designed for
+    #                       cases where the option values (e.g. password) are automatically rotated on
+    #                       a regular basis without involvement from the application using Sequel.
     # :default_string_column_size :: The default size of string columns, 255 by default.
     # :extensions :: Extensions to load into this Database instance.  Can be a symbol, array of symbols,
     #                or string with extensions separated by columns.  These extensions are loaded after

spec/core/database_spec.rb

@@ -23,6 +23,21 @@
     Sequel::Database.new(1 => 2, :logger => [4], :loggers => [3]).loggers.must_equal [4,3]
   end
 
+  it "should support :connect_opts_proc option to modify options passed when connecting" do
+    c = Class.new(Sequel::Database) do
+      alias connect server_opts
+    end
+    opts = {:a => 1, :connect_opts_proc=>lambda{|h| h[:a] += 2; h[:b] = 4}}
+    c.new(opts).synchronize do |c|
+      c[:a].must_equal 3
+      c[:b].must_equal 4
+    end
+    c.new(opts.merge(:servers=>{:default=>{:a=>5}})).synchronize do |c|
+      c[:a].must_equal 7
+      c[:b].must_equal 4
+    end
+  end
+
   it "should support :preconnect option to preconnect to database" do
     @db.pool.size.must_equal 0
     c = Class.new(Sequel::Database) do