Gracefully handle duplicate dotenv keys

app/services/ci/parse_dotenv_artifact_service.rb

@@ -33,13 +33,13 @@ module Ci
     end
 
     def parse!(artifact)
-      variables = []
+      variables = {}
 
       artifact.each_blob do |blob|
         blob.each_line do |line|
           key, value = scan_line!(line)
 
-          variables << Ci::JobVariable.new(job_id: artifact.job_id,
+          variables[key] = Ci::JobVariable.new(job_id: artifact.job_id,
             source: :dotenv, key: key, value: value)
         end
       end
@@ -49,7 +49,7 @@ module Ci
           "Dotenv files cannot have more than #{dotenv_variable_limit} variables"
       end
 
-      variables
+      variables.values
     end
 
     def scan_line!(line)

doc/ci/yaml/artifacts_reports.md

@@ -169,6 +169,11 @@ The `dotenv` report collects a set of environment variables as artifacts.
 The collected variables are registered as runtime-created variables of the job,
 which you can use to [set dynamic environment URLs after a job finishes](../environments/index.md#set-dynamic-environment-urls-after-a-job-finishes).
 
+If duplicate environment variables are present in a `dotenv` report:
+
+- In GitLab 14.6 and later, the last one specified is used.
+- In GitLab 14.5 and earlier, an error occurs.
+
 The exceptions to the [original dotenv rules](https://github.com/motdotla/dotenv#rules) are:
 
 - The variable key can contain only letters, digits, and underscores (`_`).

spec/services/ci/parse_dotenv_artifact_service_spec.rb

@@ -37,6 +37,32 @@ RSpec.describe Ci::ParseDotenvArtifactService do
         end
       end
 
+      context 'when dotenv variables have duplicate variables' do
+        let!(:artifact) { create(:ci_job_artifact, :dotenv, job: build) }
+        let(:blob) do
+          <<~EOS
+            KEY1=VAR1
+            KEY2=VAR2
+            KEY2=VAR3
+            KEY1=VAR4
+          EOS
+        end
+
+        before do
+          allow(artifact).to receive(:each_blob).and_yield(blob)
+        end
+
+        it 'latest values get used' do
+          subject
+
+          expect(subject[:status]).to eq(:success)
+
+          expect(build.job_variables.as_json).to contain_exactly(
+            hash_including('key' => 'KEY1', 'value' => 'VAR4'),
+            hash_including('key' => 'KEY2', 'value' => 'VAR3'))
+        end
+      end
+
       context 'when parse error happens' do
         before do
           allow(service).to receive(:scan_line!) { raise described_class::ParserError, 'Invalid Format' }