Allow just one parallel job

Changelog: changed

doc/ci/yaml/index.md

@@ -2905,7 +2905,7 @@ Parallel jobs are named sequentially from `job_name 1/N` to `job_name N/N`.
 
 **Possible inputs**:
 
-- A numeric value from `2` to `200`.
+- A numeric value from `1` to `200`.
 
 **Example of `parallel`**:
 

lib/gitlab/ci/config/entry/product/parallel.rb

@@ -19,7 +19,7 @@ class ParallelBuilds < ::Gitlab::Config::Entry::Node
 
               validations do
                 validates :config, numericality: { only_integer: true,
-                                                   greater_than_or_equal_to: 2,
+                                                   greater_than_or_equal_to: 1,
                                                    less_than_or_equal_to: Entry::Product::Parallel::PARALLEL_LIMIT },
                                    allow_nil: true
 

spec/lib/gitlab/ci/config/entry/job_spec.rb

@@ -261,13 +261,13 @@
           end
         end
 
-        context 'when it is lower than two' do
-          let(:config) { { script: 'echo', parallel: 1 } }
+        context 'when it is lower than one' do
+          let(:config) { { script: 'echo', parallel: 0 } }
 
           it 'returns error about value too low' do
             expect(entry).not_to be_valid
             expect(entry.errors)
-              .to include 'parallel config must be greater than or equal to 2'
+              .to include 'parallel config must be greater than or equal to 1'
           end
         end
 

spec/lib/gitlab/ci/config/entry/product/parallel_spec.rb

@@ -27,10 +27,10 @@
       it_behaves_like 'invalid config', /should be an integer or a hash/
     end
 
-    context 'when it is lower than two' do
-      let(:config) { 1 }
+    context 'when it is lower than one' do
+      let(:config) { 0 }
 
-      it_behaves_like 'invalid config', /must be greater than or equal to 2/
+      it_behaves_like 'invalid config', /must be greater than or equal to 1/
     end
 
     context 'when it is bigger than 200' do

spec/lib/gitlab/ci/config/normalizer/number_strategy_spec.rb

@@ -53,6 +53,22 @@
       end
     end
 
+    shared_examples 'single parallelized job' do
+      it { expect(subject.size).to eq(1) }
+
+      it 'has attributes' do
+        expect(subject.map(&:attributes)).to match_array(
+          [
+            { name: 'test 1/1', instance: 1, parallel: { total: 1 } }
+          ]
+        )
+      end
+
+      it 'has parallelized name' do
+        expect(subject.map(&:name)).to match_array(['test 1/1'])
+      end
+    end
+
     context 'with numbers' do
       let(:config) { 3 }
 
@@ -64,5 +80,11 @@
 
       it_behaves_like 'parallelized job'
     end
+
+    context 'with one' do
+      let(:config) { 1 }
+
+      it_behaves_like 'single parallelized job'
+    end
   end
 end