discourse · tgxworld · Jul 24, 2025
diff --git a/config/initializers/000-pg-connection-debug.rb b/config/initializers/000-pg-connection-debug.rb
diff --git a/config/initializers/000-pg_connection_patch.rb b/config/initializers/000-pg_connection_patch.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+class ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
+  def self.new_client(conn_params)
+    start = Time.now()
+    PG.connect(**conn_params)
+  rescue ::PG::Error => error
+    if conn_params && conn_params[:dbname] == "postgres"
+      raise ActiveRecord::ConnectionNotEstablished, error.message
+      # === PATCH START ===
+      # PostgreSQL's error message for a missing database looks something like this `FATAL:  database "<databasename>" does not exist`.
+      # This patch updates the following conditional to be stricter and not match on other error messages that may contain the database name.
+      # For example, `<database>-some-host" (<some IP>), port 5432 failed: timeout expired after 11.30376464s` should not be considered
+      # a missing database error.
+      #
+      # Ideally, we want to include more of the missing database error message but we are unsure if the error message
+      # will change based on a user's locale and whether the locale is even selectable. The workaround now is already much better
+      # than the existing conditional.
+    elsif conn_params && conn_params[:dbname] &&
+          error.message.include?("\"#{conn_params[:dbname]}\"")
+      raise ActiveRecord::NoDatabaseError.db_error(conn_params[:dbname])
+      # === PATCH END ===
+    elsif conn_params && conn_params[:user] && error.message.include?(conn_params[:user])
+      # === PATCH START ===
+      error_message =
+        ActiveRecord::DatabaseConnectionError.username_error(conn_params[:user]).message
+      raise ActiveRecord::DatabaseConnectionError.new("#{error_message}\n#{error.message}")
+      # === PATCH END ===
+    elsif conn_params && conn_params[:host] && error.message.include?(conn_params[:host])
+      # === PATCH START ===
+      error_message =
+        ActiveRecord::DatabaseConnectionError.hostname_error(conn_params[:host]).message
+      raise ActiveRecord::DatabaseConnectionError.new("#{error_message}\n#{error.message}")
+      # === PATCH END ===
+    else
+      raise ActiveRecord::ConnectionNotEstablished, error.message
+    end
+  end
+end
diff --git a/spec/initializers/000_pg_connection_patch_spec.rb b/spec/initializers/000_pg_connection_patch_spec.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+RSpec.describe "Patching ActiveRecord::ConnectionAdapters::PostgreSQLAdapter#new_client" do
+  it "raises ActiveRecord::NoDatabaseError for a missing database" do
+    conn_params = { dbname: "non_existent_db" }
+
+    expect do
+      ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.new_client(conn_params)
+    end.to raise_error(ActiveRecord::NoDatabaseError, /non_existent_db/)
+  end
+
+  it "raises ActiveRecord::DatabaseConnectionError when error message contains the `host` connection params" do
+    conn_params = { host: "some-host", user: "test_user" }
+
+    PG.expects(:connect).raises(
+      ::PG::Error.new(
+        "connection to server at \"some-host.name\" (::1), port 6432 failed: timeout expired after 11.30376464s",
+      ),
+    )
+
+    expect do
+      ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.new_client(conn_params)
+    end.to raise_error(
+      ActiveRecord::DatabaseConnectionError,
+      /connection to server at "some-host.name"/,
+    )
+  end
+
+  it "raises ActiveRecord::DatabaseConnectionError when error message contains the `user` connection params" do
+    conn_params = { user: "test_user" }
+
+    PG.expects(:connect).raises(
+      ::PG::Error.new("FATAL:  password authentication failed for user \"test_user\""),
+    )
+
+    expect do
+      ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.new_client(conn_params)
+    end.to raise_error(
+      ActiveRecord::DatabaseConnectionError,
+      /password authentication failed for user "test_user"/,
+    )
+  end
+end