exec-maven-plugin says cannot run specified program, even though it is on the PATH

Question

Edit 20140716:

Solution found

tl;dr = exec-maven-plugin does not recognise .cmd files, but only .bat files, as executable scripts. Rename grunt.cmd --> grunt.bat, bower.cmd --> bower.bat, etc. as a workaround.

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Having done npm install -g grunt-cli on my system, grunt is most certainly on the PATH

When I run maven install however, this doesn't seem to register.

    [ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:exec 
    (build-spa-bower) on project foobar: Command execution failed. 
    Cannot run program "grunt" (in directory "C:\workspace\foobar\src\main\spa"): 
    CreateProcess error=2, The system cannot find the file specified -> [Help 1]
    org.apache.maven.lifecycle.LifecycleExecutionException: 
    Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:exec 
    (build-spa-bower) on project foobar: Command execution failed.

Just to be sure, in the same terminal, I have executed this

cd C:\workspace\foobar\src\main\spa
grunt build

... in the same terminal as I issued the maven command above, and grunt executes just fine.

Does exec-maven-plugin use the PATH environment variable, or does it need to be told that this executable exisst in some other way?

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EDIT:

This documentation suggests that executables on PATH should be found, so it stumps me further.

Answer 1

I dug into the source code of exec-maven-plugin and found this snippet.

From the source of ExecMojo#getExecutablePath:

    CommandLine toRet;
    if ( OS.isFamilyWindows() && exec.toLowerCase( Locale.getDefault() ).endsWith( ".bat" ) )
    {
        toRet = new CommandLine( "cmd" );
        toRet.addArgument( "/c" );
        toRet.addArgument( exec );
    }
    else
    {
        toRet = new CommandLine( exec );
    }

I compared this to another plugin that ran grunt tasks from maven, and found this

        if (isWindows()) {
            command = "cmd /c " + command;
        }

... and that worked for me. So essentially the latter worked because all commands in WIndows were prepended with cmd /c, whereas the exec-maven-plugin did not, because it only did so for file ending in .bat.

Looking in C:\Users\USER\AppData\Roaming\npm, I see:

• node_modules (folder)
• grunt (unix script file)
• grunt.cmd (windows script file)

When I rename grunt.cmd --> grunt.bat, this solves the problem, and exec-maven-plugin is able to run this command.

(this also applies to other executables created using npm install -g, such as bower and yo)