Fix azure packer plugin output parsing

A feature was added to the azure packer plugin to support multiple
output formats.  As part of this change, the expected "OSDiskUri" log
message was namespaced to "VHDOSDiskUri".

We made this code a bit more resilient, and it looks for a match instead
of a exact starting string.

ref: hashicorp/packer-plugin-azure#522

Co-authored-by: Aram Price <[email protected]>

Author: selzoc

lib/stemcell/builder/azure.rb

@@ -72,9 +72,11 @@ def parse_packer_output(packer_output)
         def parse_disk_uri(line)
           return unless line.include?("azure-arm,artifact,0") && line.include?("OSDiskUri:")
 
-          os_disk_uri = (line.split '\n').select do |s|
-            s.start_with?("OSDiskUri: ")
-          end.first.gsub("OSDiskUri: ", "").strip
+          os_disk_uri = line.split('\n')
+                          .find { |s| s.match?("OSDiskUri") }
+                          .split(": ")
+                          .last
+                          .strip
 
           create_signed_url(os_disk_uri)
         end

spec/stemcell/builder/azure_spec.rb

@@ -19,7 +19,7 @@
         command = 'build'
         manifest_contents = 'manifest_contents'
         packer_vars = {some_var: 'some-value'}
-        disk_image_url = 'some-disk-image-url'
+        disk_image_url = 'https://some-disk-image-url'
         client_id = 'some-client-id'
         client_secret = 'some-client-secret'
         tenant_id = 'some-tenant-id'
@@ -32,7 +32,7 @@
         offer = 'some-offer'
         sku = 'some-sku'
         vm_prefix = 'some-vm-prefix'
-        packer_output = "azure-arm,artifact,0\\nOSDiskUri: #{disk_image_url}"
+        packer_output = "azure-arm,artifact,0\\nVHDOSDiskUri: #{disk_image_url}"
 
         packer_config = double(:packer_config)
         allow(packer_config).to receive(:dump).and_return(config)