[ruby-core:105538] [Ruby master Feature#18231] `RubyVM.keep_script_lines`

Issue #18231 has been updated by Eregon (Benoit Daloze).


We already have something similar to "code locations" objects: `Thread::Backtrace::Location`.
We could add `#{first,last}_{column,line}` and `#code` to `Thread::Backtrace::Location`, how about that?
And then add a way to get a `Thread::Backtrace::Location` from a Method.

In Truffle terminology each code is backed by a `Source` object and each method/AST node has a `SourceSection`, equivalent to these "code locations".

If we make this new API dependent on RubyVM, we give up needlessly on having both `error_highlight` and the `debug` gems working on non-CRuby.
I'd say that's a shame, because there is no need.

----------------------------------------
Feature #18231: `RubyVM.keep_script_lines`
https://bugs.ruby-lang.org/issues/18231#change-93994

* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* Target version: 3.1
----------------------------------------
This ticket proposes the method `RubyVM.keep_script_lines` to manage the flag to keep the source code.

Now, `SCRIPT_LINES__ = {}` constant is defined, the hash will stores the compiled script with a path name (`{path => src}`). However, `eval` source code doesn't stores in it (maybe because it can be bigger and bigger).

## Proposal

This proposal to add script lines to the ISeq and AST.

```ruby
RubyVM::keep_script_lines = true

eval("def foo = nil\ndef bar = nil")
pp RubyVM::InstructionSequence.of(method(:foo)).script_lines
#=> ["def foo = nil\n", "def bar = nil"]
```

In this case, methods `foo` and `bar` are defined by `eval()` and ISeq of `foo` can returns script lines (all script for `eval`).
`ISeq#script_lines` returns compiled script lines.

When `ISeq` is GCed, then the source code will be also free'ed.

## Discussion

* This feature will be used by debugger (to show the source code) or REPL support (irb and so on) with `error_highlight`.
* Of course memory usage will be increased.
* We can introduce new status `only_eval` in future which will help REPL systems.
* We can implement `ISeq#source` method like `AST#source` method (similar to `toSource` in JavaScript), but this ticket doesn't contain it.

## Implementation

https://github.com/ruby/ruby/pull/4913

For the Ractor support script lines object should be immutable (not implemented yet).




-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>