CLI: `build_spec` raises `NoMethodError` when a code object has no associated source file

[jcouball]

Summary

build_spec calls .join on the return value of Array#first without guarding against nil. If YARD ever returns a code object whose files array is empty, the call raises NoMethodError and the entire test-examples pipeline crashes.

Location

lib/yard/cli/test_examples.rb — build_spec

spec.filepath = "#{Dir.pwd}/#{example.object.files.first.join(':')}"

When can files be empty?

YARD::CodeObject#files returns an empty array for objects that YARD could not associate with a source location — for example:

• Objects defined entirely in C extensions loaded as .so/.bundle files.
• Objects synthesised by YARD plugins or macros that do not set file information.
• Objects documented in a yard file (.yardoc cache) whose original source has since been deleted.

All of these are unusual but can occur when users run yard test-examples against a project that mixes Ruby and native extensions.

Current behaviour

NoMethodError: undefined method 'join' for nil
  from lib/yard/cli/test_examples.rb:…:in 'build_spec'

The crash surfaces as an unhandled exception from generate_tests, aborting the entire run rather than just skipping the offending example.

Proposed solution

Guard against a missing first entry and fall back to a placeholder:

spec.filepath = if (file_info = example.object.files.first)
                  "#{Dir.pwd}/#{file_info.join(':')}"
                else
                  example.object.path
                end

Or more concisely:

spec.filepath = example.object.files.first&.then { |f| "#{Dir.pwd}/#{f.join(':')}" } ||
                example.object.path

The fallback of the YARD path ensures failure messages still identify the object even when no file location is available.

Acceptance criteria

• build_spec does not raise when example.object.files is empty
• A meaningful value is still assigned to spec.filepath
• All existing cucumber scenarios continue to pass