Correctly process Bamboo API results

Bamboo API returns an array of results as per
https://docs.atlassian.com/atlassian-bamboo/REST/6.2.5/#d2e786

app/models/project_services/bamboo_service.rb

@@ -80,13 +80,18 @@ class BambooService < CiService
 
   private
 
+  def get_build_result_index
+    # When Bamboo returns multiple results for a given changeset, arbitrarily assume the most relevant result to be the last one.
+    -1
+  end
+
   def read_build_page(response)
-    if response.code != 200 || response['results']['results']['size'] == '0'
+    if response.code != 200 || response.dig('results', 'results', 'size') == '0'
       # If actual build link can't be determined, send user to build summary page.
       URI.join("#{bamboo_url}/", "browse/#{build_key}").to_s
     else
       # If actual build link is available, go to build result page.
-      result_key = response['results']['results']['result']['planResultKey']['key']
+      result_key = response.dig('results', 'results', 'result', get_build_result_index, 'planResultKey', 'key')
       URI.join("#{bamboo_url}/", "browse/#{result_key}").to_s
     end
   end
@@ -94,10 +99,10 @@ class BambooService < CiService
   def read_commit_status(response)
     return :error unless response.code == 200 || response.code == 404
 
-    status = if response.code == 404 || response['results']['results']['size'] == '0'
+    status = if response.code == 404 || response.dig('results', 'results', 'size') == '0'
                'Pending'
              else
-               response['results']['results']['result']['buildState']
+               response.dig('results', 'results', 'result', get_build_result_index, 'buildState')
              end
 
     if status.include?('Success')

changelogs/unreleased/21970-fix-bamboo-results.yml

@@ -0,0 +1,5 @@
+---
+title: "Correctly process Bamboo API result array"
+merge_request: 21970
+author: Alex Lossent
+type: fixed

spec/models/project_services/bamboo_service_spec.rb

@@ -245,6 +245,7 @@ describe BambooService, :use_clean_rails_memory_store_caching do
   end
 
   def bamboo_response(result_key: 42, build_state: 'success', size: 1)
-    %Q({"results":{"results":{"size":"#{size}","result":{"buildState":"#{build_state}","planResultKey":{"key":"#{result_key}"}}}}})
+    # reference: https://docs.atlassian.com/atlassian-bamboo/REST/6.2.5/#d2e786
+    %Q({"results":{"results":{"size":"#{size}","result":[{"buildState":"#{build_state}","planResultKey":{"key":"#{result_key}"}}]}}})
   end
 end