* Exclude substitution refinement on pipelines.yml (applies on ENV vars and logstash.yml where env2yaml saves vars)
* Safety integration test for pipeline config.string contains ENV .
* source/multilocal: fix detection of empty pipelines.yml
Fixes a regression introduced in elastic/logstash#13883 in which the presence
of an empty `pipelines.yml` file produces an error message indicating that
the file cannot be read.
When either `YAML::load` or `YAML::safe_load` encounter an effectively-empty
payload (such as one that is entirely comments), they use a `fallback` param
to determine what value to emit, with the former emitting `false` and the
latter emitting `nil`.
This is problematic because a _separate_ blind-`rescue nil` causes `nil` to
be bound to the MultiLocal's `@detected_marker`, and we assume that a `nil`
value in the marker means that there was an exception reading the file (such
as a permissions issue or parse failure).
By providing a `fallback: false` directive when parsing the contents, we
ensure that an empty file is reported as such.
* source/multilocal: avoid `rescue nil` that loses helpful context
When the pipelines yaml cannot be read, or can be read but fails to parse,
the MultiLocal#read_pipelines_from_yaml emits a helpful exception including
specifics about why it failed to load or parse, but a blind `rescue nil`
here causes that helpful information to be lost.
When pipeline detection is exceptional, hold onto the helpful exception
so that it can be reported along with the config conflicts.
* source/multilocal: differentiate between reading and parsing failure
* source/multilocal: use translations for conflict messages
* source/multilocal: specs for error conditions
This commit replaces the use of a block with a lambda as an argument for Stream.forEach.
This is to work around the jruby issue identified in https://github.com/jruby/jruby/issues/7246.
This commit also updates the multiple_pipeline_spec to update the test case for pipeline->pipeline
communication to trigger the issue - it only occurs with Streams with more than one event in it.
