How to know where ERB stopped?

Ruby
1

Let’s say I’ve got an ERB template:

text1
<%= thing1() %>
text2
<%= thing2() %>
text3
<%= thing3() %>
text4

But let’s say we get an error (exception) during the execution of
thing2(). How can I find out that this is where the error occurred? I
don’t want to instrument thing1, thing2, thing3, etc; I’m hoping I can
just find out what ERB was doing when we errored out. Thx - m.

2

matt neuburg wrote:

Let’s say I’ve got an ERB template:

text1
<%= thing1() %>
text2
<%= thing2() %>
text3
<%= thing3() %>
text4

But let’s say we get an error (exception) during the execution of
thing2(). How can I find out that this is where the error occurred? I
don’t want to instrument thing1, thing2, thing3, etc; I’m hoping I can
just find out what ERB was doing when we errored out. Thx - m.

The following code illustrates how this could be accomplished (also
available as a pastie1):

require ‘erb’

def thing1(); “foo” end
def thing2(); raise Exception.new(“Something went wrong”) end
def thing3(); “bar” end

template = <<ERB
text1
<%= thing1() %>
text2
<%= thing2() %>
text3
<%= thing3() %>
text4
ERB

erb = ERB.new(template)

begin
erb.run
rescue Exception => e
puts “Exception: #{e}”
line = e.backtrace.grep(/^(erb)/)[0].split(‘:’)1.to_i
puts “While evaluating line #{line} of the template:”
puts template.split(“\n”)[line-1]
puts "Backtrace: ", e.backtrace
end

Hope that helps!

-Matthias

3

Matthias R. [email protected] wrote:

def thing1(); “foo” end
text4
puts template.split(“\n”)[line-1]
puts "Backtrace: ", e.backtrace
end

Hope that helps!

Very much so, thank you. Grepping and parsing the backtrace is the exact
clue that I needed. m.