Adds support for per = 0

When running a Scope with `per: 0` only the count query will
be executed.

lib/simple/sql/connection_adapter.rb

@@ -64,10 +64,9 @@ def ask(sql, *args, into: nil)
 
   def add_page_info(scope, results)
     raise ArgumentError, "expect Array but get a #{results.class.name}" unless results.is_a?(Array)
-    raise ArgumentError, "per must be > 0" unless scope.per > 0
 
     # optimization: add empty case (page <= 1 && results.empty?)
-    if scope.page <= 1 && results.empty?
+    if scope.page <= 1 && scope.per > 0 && results.empty?
       Scope::PageInfo.attach(results, total_count: 0, per: scope.per, page: 1)
     else
       sql = "SELECT COUNT(*) FROM (#{scope.order_by(nil).to_sql(pagination: false)}) simple_sql_count"
@@ -80,6 +79,8 @@ def exec_logged(sql_or_scope, *args)
     if sql_or_scope.is_a?(Scope)
       raise ArgumentError, "You cannot call .all with a scope and additional arguments" unless args.empty?
 
+      return [] if sql_or_scope.per == 0
+
       sql  = sql_or_scope.to_sql
       args = sql_or_scope.args
     else
@@ -92,6 +93,8 @@ def exec_logged(sql_or_scope, *args)
   end
 
   def enumerate(result, into:, &block)
+    return result if result.is_a?(Array) && result.empty?
+
     decoder = Decoder.new(self, result, into: into)
 
     if block

lib/simple/sql/scope.rb

@@ -53,7 +53,7 @@ def where(sql_fragment, arg = :__dummy__no__arg, placeholder: "?")
   end
 
   # Set pagination
-  def paginate(per:, page:)
+  def paginate(per:, page: 1)
     duplicate.send(:paginate!, per: per, page: page)
   end
 
@@ -126,7 +126,7 @@ module PageInfo
     def self.attach(results, total_count:, per:, page:)
       results.extend(self)
       results.instance_variable_set :@total_count, total_count
-      results.instance_variable_set :@total_pages, (total_count + (per - 1)) / per
+      results.instance_variable_set :@total_pages, per > 0 ? (total_count + (per - 1)) / per : -1
       results.instance_variable_set :@current_page, page
       results
     end

spec/simple/sql_scope_spec.rb

@@ -140,6 +140,18 @@ def expects(expected_result, sql, *args)
       end
     end
 
+    context "with per=0" do
+      let(:result) { SQL.all(scope.paginate(per: 0)) }
+
+      it "returns an empty result set" do
+        expect(result).to eq([])
+      end
+
+      it "adds total_count info to the .all return value" do
+        expect(result.total_count).to eq(2)
+      end
+    end
+
     context "with per=2" do
       it "returns an empty array after the last page" do
         result = SQL.all(scope.paginate(per: 2, page: 2))