# How to require Ruby 1.9 from a required file?

**URL:** <https://www.ruby-forum.com/t/how-to-require-ruby-1-9-from-a-required-file/194545>\
**Category:** Ruby\
**Created:** [September 6, 2010, 10:39pm UTC](https://www.ruby-forum.com/t/how-to-require-ruby-1-9-from-a-required-file/194545 "2010-09-06T22:39:11Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![sackerson](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/59ef9b/32.png) [@sackerson](https://www.ruby-forum.com/u/sackerson)\
**Post date:** [September 6, 2010, 10:39pm UTC](https://www.ruby-forum.com/t/how-to-require-ruby-1-9-from-a-required-file/194545/1 "2010-09-06T22:39:11Z")

</div>

Is there any way to require Ruby 1.9 from a required file such that I  
can trigger an error message before the main file is parsed?

Suppose I’m making a DSL that depends on the very nice Ruby 1.9 hash  
syntax. Here’s an example:

app.rb

```
$LOAD_PATH << File.dirname( __FILE__ )
require 'my_library'

make_pie apple:2, butter:1, flour:4
puts "bye"

```

in my\_library I want to report an error if we’re not running with 1.9,  
so I did this:

```
if RUBY_VERSION < "1.9.0"
  abort <<-end_message
    This requires Ruby 1.9
  end_message
end

def make_pie options
  return unless options.respond_to? :key
  puts "with " + options.keys.join(',') + " we can make a great pie"
end

```

It works great as long as I don’t have Ruby 1.9 syntax in the main file,  
but when I do, Ruby 1.8.7 will show that error first.

```
$ rvm use 1.9.2-head
Using ruby 1.9.2 head
$ ruby app.rb
with apple,butter,flour we can make a great pie
bye
$ rvm use 1.8.7
Using ruby 1.8.7 p249
$ ruby app.rb
app.rb:4: syntax error, unexpected tINTEGER, expecting

```

tSTRING\_CONTENT or tSTRING\_DBEG or tSTRING\_DVAR or tSTRING\_END  
make\_pie apple:2, butter:1, flour:4  
^

I posted the files at: [GitHub - ultrasaurus/ruby\_version\_check: understanding how to require Ruby 1.9](http://github.com/ultrasaurus/ruby_version_check)

Sure this can be solved with documentation OR changing the syntax of my  
DSL to use 1.8.7, but I was hoping for a nicer solution for end users  
(who are expected to be kids).

Thanks in advance,

Sarah

[http://www.ultrasaurus.com](http://www.ultrasaurus.com)

> **[Home | Blazing Cloud - Strategy & Design, Mobile Apps & Websites](https://blazingcloud.net)**
>
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---

<div class="post-metadata">

**Author:** ![sackerson](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/59ef9b/32.png) [@sackerson](https://www.ruby-forum.com/u/sackerson)\
**Post date:** [September 7, 2010, 2:07am UTC](https://www.ruby-forum.com/t/how-to-require-ruby-1-9-from-a-required-file/194545/2 "2010-09-07T02:07:49Z")

</div>

On Mon, Sep 6, 2010 at 9:40 PM, Sarah A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> end  
> Using ruby 1.9.2 head
> 
> I posted the files at: [GitHub - ultrasaurus/ruby\_version\_check: understanding how to require Ruby 1.9](http://github.com/ultrasaurus/ruby_version_check)
> 
> Sure this can be solved with documentation OR changing the syntax of my  
> DSL to use 1.8.7, but I was hoping for a nicer solution for end users  
> (who are expected to be kids).
> 
> Thanks in advance,
> 
> Sarah

You can’t catch a SyntaxError in same file in which it occurs (if you  
think about it - your rescue statement has to come after the place  
where the syntax error has already occurred). You ~can~ catch a  
SyntaxError in eval’d or loaded code. So, instead of requiring your  
library, why not use a script loader like this:

file: recipe-dsl

#!/usr/bin/env ruby  
def make\_pie(params)  
p params  
end

begin  
load ARGV[0]  
rescue SyntaxError =\> e  
if RUBY\_VERSION \< ‘1.9.0’  
puts “You need ruby 1.9.x to run this script”  
else  
raise  
end  
end

which you use to run the DSL scripts like so:

$ recipe-dsl ~/apple-pie.recipe

where apple-pie.recipe contains just your DSL statements:

file: apple-pie.recipe

make\_pie apple: 2, butter: 1, flour: 4

If you try to run this under 1.8.x, you’ll get:

$ ./recipe-dsl apple-pie.recipe  
You need ruby 1.9.x to run this script

If you really do have a syntax error in your recipe script, that will  
be reported under 1.9.x.

HTH

Regards,  
Sean

---

<div class="post-metadata">

**Author:** ![sackerson](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/59ef9b/32.png) [@sackerson](https://www.ruby-forum.com/u/sackerson)\
**Post date:** [September 8, 2010, 2:47am UTC](https://www.ruby-forum.com/t/how-to-require-ruby-1-9-from-a-required-file/194545/3 "2010-09-08T02:47:46Z")

</div>

Sean O’halpin wrote:

> You can’t catch a SyntaxError in same file in which it occurs (if you  
> think about it - your rescue statement has to come after the place  
> where the syntax error has already occurred). You ~can~ catch a  
> SyntaxError in eval’d or loaded code. So, instead of requiring your  
> library, why not use a script loader like this:
> 
> file: recipe-dsl
> 
> #!/usr/bin/env ruby  
> def make\_pie(params)  
> p params  
> end
> 
> begin  
> load ARGV[0]  
> rescue SyntaxError =\> e  
> if RUBY\_VERSION \< ‘1.9.0’  
> puts “You need ruby 1.9.x to run this script”  
> else  
> raise  
> end  
> end

Or:

my\_library.rb:  
#!/usr/bin/env ruby  
abort “You need ruby 1.9.x to run this script” if RUBY\_VERSION \<  
“1.9.0”  
load ‘my\_library\_1.9’

if you know your libraries Ruby 1.9-dependencies aren’t limited to  
constructs that would be syntactic errors in Ruby 1.8, so you don’t want  
the error message to depend on the presence of syntax errors.

This generalizes to:

my\_library.rb:  
#!/usr/bin/env ruby  
case  
when RUBY\_VERSION \>= “1.9.0” then load ‘my\_library\_1.9’  
else load ‘my\_library\_1.8’  
end

if you add an Ruby 1.8 implementation.

---

<div class="post-metadata">

**Author:** ![sackerson](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/59ef9b/32.png) [@sackerson](https://www.ruby-forum.com/u/sackerson)\
**Post date:** [September 8, 2010, 3:56am UTC](https://www.ruby-forum.com/t/how-to-require-ruby-1-9-from-a-required-file/194545/4 "2010-09-08T03:56:54Z")

</div>

Sarah A. wrote:

> Is there any way to require Ruby 1.9 from a required file such that I  
> can trigger an error message before the main file is parsed?
> 
> Suppose I’m making a DSL that depends on the very nice Ruby 1.9 hash  
> syntax. […]  
> […]  
> Sure this can be solved with documentation OR changing the syntax of my  
> DSL to use 1.8.7, but I was hoping for a nicer solution for end users  
> (who are expected to be kids).

Unfortunately, no.

Ruby 1.8.8 is supposed to be syntactically compatible with Ruby 1.9,  
specifically to solve the very problem you are having. So, in Ruby  
1.8.8, just _parsing_ Ruby 1.9 code should not result in an error,  
only actually _running_ it. But obviously, Ruby 1.8.8 isn’t out yet,  
and if you could get the kids to upgrade to Ruby 1.8.8, you could  
presumably get them to upgrade to Ruby 1.9.2 as well, so …

jwm