[PATCH] showexceptions: gracefully handle empty backtraces

[PATCH] showexceptions: gracefully handle empty backtraces

[Eric Wong]

Also pushed out to the "showexceptions" branch of
  git://git.bogomips.org/rack.git

http://git.bogomips.org/cgit/rack.git/commit/?id=bfb59e0f92271f8ecb60e5b7146c1b6e656938b8

From bfb59e0f92271f8ecb60e5b7146c1b6e656938b8 Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Fri, 8 Oct 2010 12:04:24 -0700
Subject: [PATCH] showexceptions: gracefully handle empty backtraces

Some HTTP servers (e.g. Unicorn and Rainbows!) raise certain
exceptions without a backtrace[1], so avoid triggering our own
NoMethodError exception because of this.

[1] - http://git.bogomips.org/cgit/unicorn.git/commit/?id=e4256da292f9626d7dfca60e08f65651a0a9139a
---
 lib/rack/showexceptions.rb  |    8 +++++++-
 test/spec_showexceptions.rb |   20 ++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletions(-)

diff --git a/lib/rack/showexceptions.rb b/lib/rack/showexceptions.rb
index 697bc41..26ff923 100644
--- a/lib/rack/showexceptions.rb
+++ b/lib/rack/showexceptions.rb
@@ -195,7 +195,13 @@ TEMPLATE = <<'HTML'
   <h2><%=h exception.message %></h2>
   <table><tr>
     <th>Ruby</th>
-    <td><code><%=h frames.first.filename %></code>: in <code><%=h frames.first.function %></code>, line <%=h frames.first.lineno %></td>
+    <td>
+<% if first = frames.first %>
+      <code><%=h first.filename %></code>: in <code><%=h first.function %></code>, line <%=h frames.first.lineno %>
+<% else %>
+      unknown location
+<% end %>
+    </td>
   </tr><tr>
     <th>Web</th>
     <td><code><%=h req.request_method %> <%=h(req.host + path)%></code></td>
diff --git a/test/spec_showexceptions.rb b/test/spec_showexceptions.rb
index 82ac918..908f7b7 100644
--- a/test/spec_showexceptions.rb
+++ b/test/spec_showexceptions.rb
@@ -20,4 +20,24 @@ describe Rack::ShowExceptions do
     res.should =~ /RuntimeError/
     res.should =~ /ShowExceptions/
   end
+
+  it "handles exceptions without a backtrace" do
+    res = nil
+
+    req = Rack::MockRequest.new(
+      Rack::ShowExceptions.new(
+        lambda{|env| raise RuntimeError, "", [] }
+    ))
+
+    lambda{
+      res = req.get("/")
+    }.should.not.raise
+
+    res.should.be.a.server_error
+    res.status.should.equal 500
+
+    res.should =~ /RuntimeError/
+    res.should =~ /ShowExceptions/
+    res.should =~ /unknown location/
+  end
 end
-- 
Eric Wong

Re: [PATCH] showexceptions: gracefully handle empty backtraces

[James Tucker]

Merged, thanks Eric!

On 8 Oct 2010, at 17:58, Eric Wong wrote:

> Also pushed out to the "showexceptions" branch of
>  git://git.bogomips.org/rack.git
> 
> http://git.bogomips.org/cgit/rack.git/commit/?id=bfb59e0f92271f8ecb60e5b7146c1b6e656938b8
> 
> From bfb59e0f92271f8ecb60e5b7146c1b6e656938b8 Mon Sep 17 00:00:00 2001
> From: Eric Wong <normalperson@yhbt.net>
> Date: Fri, 8 Oct 2010 12:04:24 -0700
> Subject: [PATCH] showexceptions: gracefully handle empty backtraces
> 
> Some HTTP servers (e.g. Unicorn and Rainbows!) raise certain
> exceptions without a backtrace[1], so avoid triggering our own
> NoMethodError exception because of this.
> 
> [1] - http://git.bogomips.org/cgit/unicorn.git/commit/?id=e4256da292f9626d7dfca60e08f65651a0a9139a
> ---
> lib/rack/showexceptions.rb  |    8 +++++++-
> test/spec_showexceptions.rb |   20 ++++++++++++++++++++
> 2 files changed, 27 insertions(+), 1 deletions(-)
> 
> diff --git a/lib/rack/showexceptions.rb b/lib/rack/showexceptions.rb
> index 697bc41..26ff923 100644
> --- a/lib/rack/showexceptions.rb
> +++ b/lib/rack/showexceptions.rb
> @@ -195,7 +195,13 @@ TEMPLATE = <<'HTML'
>   <h2><%=h exception.message %></h2>
>   <table><tr>
>     <th>Ruby</th>
> -    <td><code><%=h frames.first.filename %></code>: in <code><%=h frames.first.function %></code>, line <%=h frames.first.lineno %></td>
> +    <td>
> +<% if first = frames.first %>
> +      <code><%=h first.filename %></code>: in <code><%=h first.function %></code>, line <%=h frames.first.lineno %>
> +<% else %>
> +      unknown location
> +<% end %>
> +    </td>
>   </tr><tr>
>     <th>Web</th>
>     <td><code><%=h req.request_method %> <%=h(req.host + path)%></code></td>
> diff --git a/test/spec_showexceptions.rb b/test/spec_showexceptions.rb
> index 82ac918..908f7b7 100644
> --- a/test/spec_showexceptions.rb
> +++ b/test/spec_showexceptions.rb
> @@ -20,4 +20,24 @@ describe Rack::ShowExceptions do
>     res.should =~ /RuntimeError/
>     res.should =~ /ShowExceptions/
>   end
> +
> +  it "handles exceptions without a backtrace" do
> +    res = nil
> +
> +    req = Rack::MockRequest.new(
> +      Rack::ShowExceptions.new(
> +        lambda{|env| raise RuntimeError, "", [] }
> +    ))
> +
> +    lambda{
> +      res = req.get("/")
> +    }.should.not.raise
> +
> +    res.should.be.a.server_error
> +    res.status.should.equal 500
> +
> +    res.should =~ /RuntimeError/
> +    res.should =~ /ShowExceptions/
> +    res.should =~ /unknown location/
> +  end
> end
> -- 
> Eric Wong