Just tried to run bootstrap script on Mac OS X and got the following error:

/Users/ystrot/bin/fantom-1.0.63/bin/fan /Users/ystrot/bin/fan/src/buildall.fan superclean
sys::ArgErr: Key already mapped: jdkHome
  fan.sys.Map.add (Map.java:140)
  fan.sys.InStream.addProp (InStream.java:704)
  fan.sys.InStream.readProps (InStream.java:681)
  fan.sys.InStream.readProps (InStream.java:563)
  fanx.util.EnvProps.read (EnvProps.java:64)
  fanx.util.EnvProps$CachedProps.<init> (EnvProps.java:96)
  fanx.util.EnvProps.refresh (EnvProps.java:35)
  fanx.util.EnvProps.get (EnvProps.java:26)
  fan.sys.Env.config (Env.java:157)
  build::BuildScript.config (BuildScript.fan:92)
  build::BuildScript.config (BuildScript.fan)
  build::BuildScript.configDir (BuildScript.fan:102)
  build::BuildScript.instance$init$build$BuildScript (BuildScript.fan:45)
  build::BuildScript.make$ (BuildScript.fan:18)
  build::BuildGroup.make$ (BuildGroup.fan:15)
  buildall_0::Build.make$ (/Users/ystrot/bin/fan/src/buildall.fan:30)
  buildall_0::Build.make (/Users/ystrot/bin/fan/src/buildall.fan:30)
  java.lang.reflect.Method.invoke (Method.java:597)
  fan.sys.Method.invoke (Method.java:559)
  fan.sys.Method$MethodFunc.callList (Method.java:198)
  7 More...

What Am I doing wrong?

It looks like you have jdkHome property mapped twice in the same file (probably your etc/build/config.props). Or maybe it is defined in multiple places and its my bug not merging things correctly.

You were right, not sure how it happened. Now it works fine!

I had the the same error on OS X El Capitan but wanted to add that I had installed Fantom via Homebrew and found the duplicate specifically had to deal with the Windows definition for jdkHome being enabled in the (OS X & macOS only) Homebrew install of of Fantom for the file:

/usr/local/Cellar/fantom/1.0.69/libexec/etc/build/config.props

Hope that sheds a little extra light. Also hoping the setting can get commented out by default for in the Homebrew setup in future releases. :-)

Hi RuneImp!

Fantom HomeBrew: http://macappstore.org/fantom/

Also hoping the setting can get commented out by default for in the HomeBrew setup in future releases. :-)

Given HomeBrew is mac only, that's a really good idea!

I think Andy is the maintainer, but this topic suggests he's wanting help with the brew formula.

Also hoping the setting can get commented out by default for in the Homebrew setup in future releases

Yeah I noticed a few things we probably need to tweak while I was in there updating to 1.0.69 - on my list to fixup

Now that I'm setup to send PR's for homebrew - I'll try to keep it up-to-date