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Feature #11868

open

Proposal for RubyVM::InstructionSequence.compile to return an object containing the syntax error information currently written to STDERR

Added by jrafanie (Joe Rafaniello) almost 6 years ago. Updated over 5 years ago.

Status:
Open
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:72458]

Description

Currently, RubyVM::InstructionSequence.compile or RubyVM::InstructionSequence.new return a new InstructionSequence for valid ruby.

For invalid syntax, a SyntaxError is raised with a message of 'compile error'. Meanwhile, the useful information, line number(s) and hint(s) to the invalid syntax location, is printed on standard error. I am proposing this information be returned as an object in the event of a SyntaxError.

For example, here's good syntax:

RubyVM::InstructionSequence.new("x =1")
# => <RubyVM::InstructionSequence:<compiled>@<compiled>>

Here's bad syntax:

RubyVM::InstructionSequence.new("puts 'hi'\n puts 'hi2'\n\nthis.is -> not -> valid $ruby:syntax")

# => SyntaxError: compile error

# The useful hint and line number(s) are on standard error:
<compiled>:4: syntax error, unexpected keyword_not, expecting keyword_do_LAMBDA or tLAMBEG
this.is -> not -> valid $ruby:syntax
              ^
<compiled>:4: syntax error, unexpected tGVAR, expecting keyword_do_LAMBDA or tLAMBEG
this.is -> not -> valid $ruby:syntax
                             ^

Some ideas:

  1. Add methods to all SyntaxError exceptions to get all parse failures. For example: syntax_error.parse_failures.each {|f| puts f.lineno; puts f.hint }. In the above example, it failed on line 4 twice and we see two "hints."

  2. Create a new method to RubyVM::InstructionSequence to check ruby syntax that would allow us to see if the syntax is valid and if not, the lineno and 'hint' for each parse failure.

Use case: Rubocop[a] and other utilities[b] are really complicated and check for valid ruby syntax by creating a process to run ruby -wc with the script.
[a] https://github.com/bbatsov/rubocop/blob/86e1acf67794bf6dd5d65812b91df475e44fa320/spec/support/mri_syntax_checker.rb#L51-L63
[b] https://github.com/ManageIQ/manageiq/blob/6725fe52222c07d576a18126d2ff825ddc6dffd0/gems/pending/util/miq-syntax-checker.rb#L8-L13

It would be nice to remove all of this complexity and use RubyVM::InstructionSequence, which already has the information we need but in a more user friendly format.

Thanks!
Joe Rafaniello


Related issues

Related to Ruby master - Feature #11951: `RubyVM::InstructionSequence.compile` should return the error message within the raised errorClosedActions
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