Improve error message for syntax error in cassette #909
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When deserializing a cassette and encountering a syntax error, the error
message can be confusing. This is exacerbated in projects using Rails'
backtrace silencer, as the error has no apparent source outside the test
itself.
One common scenario resulting in syntax errors is the use of ERB in the
cassette, but omitting the `:erb` option to `use_cassette`.
For example, a cassette containing may contain a JSON snippet for an API
call where a field is populated using
"field": <%= "some computed value".to_json %>
If given `erb: true`, this will work fine, but if this is forgotten, a
syntax error will be encountered.
This change appends to the error's message, indicating that the error
was encountered reading a VCR cassette, and suggesting the use of the
`:erb` option.
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| # @private | ||
| ENCODING_ERRORS = [ArgumentError] | ||
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| # @private | ||
| SYNTAX_ERRORS = [::Psych::SyntaxError] |
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In my tests, this was always the error I encountered, regardless of if I was using Psych or not.
I'm assuming this is because under the hood Syck is gone, and Psych is still used?
My concerns are
- on a version of Ruby prior to the introduction of
Psych, will this blow up if the constant doesn't exist? - on a version of Ruby with both
SyckandPsych, will this simply not work?
I'm not intimately familiar with the subtleties of Ruby's YAML library history though, so ideally someone who is can chime in, as I may be misunderstanding what's going on.
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I wouldn't worry about that, our earliest-supported version is Ruby 2.5.
How I reasoned: In the notes at the end of the docs, https://ruby-doc.org/stdlib-2.5.3/libdoc/yaml/rdoc/YAML.html it's mentioned that Syck was the predecessor, and that Psych is the "implementation".
| def handle_syntax_errors | ||
| yield | ||
| rescue *self::SYNTAX_ERRORS => e | ||
| e.message << "\nNote: This is a VCR cassette. If it is using ERB, you may have forgotten to pass the `:erb` option to `use_cassette`." |
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I had to go and look if it << was alright to use with an exception, and it IS
$ RUBYOPT=--enable-frozen_string_literal pry
09:31:52 >> e = RuntimeError.new
=> #<RuntimeError: RuntimeError>
09:32:02 >> e.message = "hi"
NoMethodError: undefined method `message=' for #<RuntimeError: RuntimeError>
Did you mean? message
from (pry):3:in `__pry__'
09:32:07 >> e.message
=> "RuntimeError"
09:32:24 >> e.message << "e"
=> "RuntimeErrore"
Yeah, versus << on other Strings:
09:31:45 >> "" << "olle"
FrozenError: can't modify frozen String: ""
from (pry):1:in `__pry__'
So, thanks!
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@sambostock Thanks! This is a valuable developer-experience improvement!
When deserializing a cassette and encountering a syntax error, the error message can be confusing. This is exacerbated in projects using Rails' backtrace silencer, as the error has no apparent source outside the test itself.
One common scenario resulting in syntax errors is the use of ERB in the cassette, but omitting the
:erboption touse_cassette.For example, a cassette containing may contain a JSON snippet for an API call where a field is populated using
If given
erb: true, this will work fine, but if this is forgotten, a syntax error will be encountered.This change appends to the error's message, indicating that the error was encountered reading a VCR cassette, and suggesting the use of the
:erboption.