Huddled Masses

Format-PoshTable (PowerBoots + DataGrid from WPFToolkit + PoshConsole) on ScreenCast or Vimeo (and PoshCode).

If you can’t view that (it requires Windows Media Player), you can check it out through Vimeo below. I apologize for the size and quality of that, I didn’t read the HD instructions ahead of time. Skip to the end for the code

A simple demo of some of the capabilities of PowerBoots and PoshConsole in the form of a grid-output function...

In July of last year I wrote a PowerShell script with the goal of allowing me to generate XML from PowerShell with a simple markup that would look a little like the resulting XML ... this week I was using that script again, and had a couple of issues that made me go back and look at the source.

While I was playing with the source and tweaking things a little bit to improve the way it handles namespaces, I started playing with the idea that I could improve the syntax. At the very least, I thought, I ought to be able to do away with all those “xe” aliases…

Well, I was able to. And what’s more, I managed to dramatically clean up the way namespaces work, and make it so that really, the only ugly part of the syntax is the initial declaration of namespaces! I’m going to start with two examples, and use them to walk you through the features

Example 1

The simplest example I could think of is to list all the files in a folder, with the file size and last modified stamp:

The output of that, when run on my formats folder, looks like this:

You can immediately see what the script does: New-XDocument (which is aliased as ‘xml’) actually generates the root xml node, so the first argument to it is the name of that node, and any other arguments become attributes … except for the script block. That script block turns into the contents of the node.

Inside the script block, PowerShell code is parsed as usual, but whenever a command that doesn’t exist is encountered, it is turned into an xml node! Pretty simple, right? Of course, if you wanted to create a node with a name that’s already taken by a PowerShell command, you can just replace file with New-XElement file, or (using aliases) xe 'file', which explicitly creates an xml node with the given name.

That’s pretty much it for our first example, so let’s look at a more complicated example, with multiple namespaces, and deeper nesting.

Example 2

This time, we’ll create an Atom document, and we’ll include some namespace extensions (including a made up one for listing my files as we did above):

There are four things you should notice, in particular:

First: the initial tag has a [XNamespace] added to it. You can specify a tag name that has a namespace by adding them together this way, or by embedding the namespace in the string like "{http://www.w3.org/2005/Atom}feed" instead. Either way works. This initial namespace becomes the default namespace for the document. If you don’t specify a namespace on tags later, they automatically belong to that one.

Second: when you want to add additional namespaces, you can do so with a custom prefix like: -dc ([XNamespace]"http://purl.org/dc/elements/1.1"), and that prefix (dc) takes on a special meaning. When you want to have a tag later on that is part of that namespace, you just prefix the tag, like dc:rights —the same way you would in XML.

Third: any number of attributes can be specified using the -name value syntax, but anything in a {scriptblock} becomes the content — and is subject to the same rules as the outer sections.

Fourth: This generates an XDocument. When you cast an XDocument to string, the xml declaration is left off, so if you want it, you need to manually add it via $XDocument.Declaration. Incidentally, XDocuments are not XMLDocuments, but they are trivially castable to them.

The output of that particular section of New-XDocument is this:

The New-XDocument script itself is on PoshCode in the Xml Module 4 along with a few interesting functions like Select-XML (which improves over the built-in by being able to ignore namespaces when you write XPath) and Remove-XmlNamespace (which was instrumental in removing namespaces for Select-Xml). There’s also a Format-Xml for pretty-printing, and a Convert-Xml for processing XSL transformations.

I’ll probably post some more examples of this in the next week or two, and I really should write some commentary about the function itself, which uses the tokenizer to discover which “commands” are really xml nodes … but for now, I’ll leave you to enjoy.

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• JSON from PowerShell (but why?) (huddledmasses.org)
• What’s in a Namespace (apache.sys-con.com)
• Ignoring Namespaces in XPath (huddledmasses.org)

I just put up a poll on the PowerShell Virtual Group to see if people are interested in a low-planning brown-bag event.

The initial question is: would you attend a weekly (or monthly) virtual brown-bag lunch if I put one together.

The idea is that we would start each session with a short collection of interesting links, tips and tricks, or connect issues, and then have a presentation or discussion or script club or open-mic session, depending on interest.

Basically, this is meant to flow, on a week-to-week basis, from script-club to formal user group presentations.

Some weeks we would have presenters from various local user groups share content they had prepared for their local groups. We would encourage you to take ownership of this time, request topics, and prepare presentations (no matter how short).

Some weeks we would have an open-format script club using our private pastebin, IRC channel, and LiveMeeting voice chat. This time could vary from real-world problem solving to scripting games and “project Euler”-style challenges.

Some weeks we would have open-mic time and solicit feedback for the PowerShell team from anyone who cared to give it. I would make an effort to make sure I wasn’t the only MVP there, so you could feel that even if there wasn’t a Microsoft employee present on a given day, your voice could be heard when you make suggestions or vent frustrations …

The point is: the format would vary a bit, and we would adjust it over time to fit whatever works the best within our virtual meeting and time constraints.

So, what do you think? Are you interested?

The Democratic leadership in Congress just announced its response to the Supreme Court’s decision in Citizens United, the case that struck down limits on independent corporate campaign expenditures.

As Lawrence Lessig put it: hopeless.

The package the Democrats are proposing is filled with ideas that either won’t work or that, if they worked, would only invite the Supreme Court to strike again.

Congress had a chance to do something real here, but rather than supporting a bold reform that would make our democracy function better, they failed; they changed nothing. And as a result, our representatives’ dependency on campaign funders — the central corrupting force acting on our government — will continue for another day.

We all knew that’s what would happen, of course. Members of Congress don’t have much incentive to buck a systems that keeps their campaign coffers full. Here’s what Change Congress has to say on the matter on their Fix Congress First! website.

The Fair Elections Now Act is the reform we need, and we still have the chance to push Congress to pass it. So far, 135 Members of the House have signed on as co-sponsors, but we must continue to urge all of our representatives to support this crucial bill. You can use our simple tool to email your members of Congress and tell them that this issue won’t fly under the radar in 2010: http://fixcongressfirst.org/email

If the Democratic Party wants to lead, then they need to show us they’re ready to lead. And if the Republican Party wants to rise back to power, they need to prove they’d use that power to enact the will of the people.

Incidentally, I think you should read professor Lawrence Lessig’s response to the changes that the Democratic leadership is proposing. The bottom line is that these changes won’t help: they won’t make Members of Congress any less dependent on special interests and corporate fundraising, and they almost certainly won’t stand up to scrutiny by the current Supreme Court.

I’ve written this up on the new website for our Rochester PowerShell group and on the old blog, and on UGSS Facebook and Twitter … and now that there’s only two days left, it’s time to mention it again, on my blog

This Wednesday, January 20, 2010 – 6:00pm

It’s a new year, and a new opportunity to get started with PowerShell. With the new year, we’re going to put a renewed focus on trying to make our meetings valuable to everyone. With that in mind, the first Rochester meeting of the upstate New York PowerShell users group in 2010 will feature two separate presentations:

Getting Started: The PowerShell Pipeline (100 Level)

• Different types of commands in PowerShell
• Variable assignment and Pipeline arguments
• Understanding the Pipe
• Why PowerShell’s pipeline is different

• Exploiting pipelines for fun and profit

Creating PowerShell script Modules (300 Level)

• Turning your script or function into a module
• What makes a function an “advanced function”
• Providing in-line help for functions
• Controlling what functions and variables your module exports

• Why you should use Module Metadata files

Everyone is welcome, from beginners to pros! Bring a friend and introduce them to PowerShell. As always, our meeting will be at New Horizons’ in Henrietta, 50 Methodist Hill Drive, Suite 50.

In order to keep things on time, we’ll be starting our presentations at 6:30 exactly, after a short pizza, wings, and networking time starting at 6pm. We only ask that if you can come early for the food you let us know ahead of time and come ready to pitch in a few dollars to help cover the cost.

PS: There will be swag. We have several books, an Arc Mouse, and copies of Windows 7 and Office 2007 to give away…

I was under the impression that module manifests allow only DATA stuff. In fact, if you try to use cmdlets or variables in them, you get the usual Data-language errors, like this:

Import-Module : The module manifest ‘C:\Modules\Test\Test.psd1’ could not be processed because it is not a valid PowerShell restricted language file. Please remove the elements that are not permitted by the restricted language: The command ‘Get-ChildItem’ is not in allowed in restricted language mode or a Data section.

Import-Module : The module manifest ‘C:\Modules\Test\Test.psd1’ could not be processed because it is not a valid PowerShell restricted language file. Please remove the elements that are not permitted by the restricted language: A variable that cannot be referenced in restricted language mode or a Data section is being referenced. Variables that can be referenced include the following: $PSCulture, $PSUICulture, $true, $false, and $null.

BUT THEN I came across this in the Windows 7 built-in BitsTransfer module:

RequiredAssemblies=Join-Path $psScriptRoot “Microsoft.BackgroundIntelligentTransfer.Management.Interop.dll”

AND IT WORKS?!

Well, that’s very weird, because Join-Path is certainly not allowed in a normal “restricted language” file, and (as you can tell from above) neither is $PsScriptRoot — in fact, as far as I know, you shouldn’t have to do that at all, since RequiredAssemblies knows enough to look in your module folder… but nevermind that, why does it work?

The Rest of the Story

So I went digging, and it turns out that although they are parsed as Restricted Language (like a “data section,” see about_Data_Sections), module manifests are allowed extra cmdlets: “Import-LocalizedData”, “ConvertFrom-StringData”, “Write-Host”, “Out-Host”, “Join-Path” and even special variables that aren’t normally allowed in data sections: specifically $PsScriptRoot which is the ModuleBase (the parent folder of the psd1) and environment variables ($Env:), plus the usual $PSCulture, $PSUICulture, and of course $true, $false, and $null.

However, although you can use those variables, you can’t embed them in strings, so if you wanted to use $Env:Windir or $Env:Temp as part of a path (for instance), you need to take advantage of the availability of Join-Path.

Now, I can’t find this documented anywhere (although I did add it to the module manifest documentation on MSDN), but it’s true, nonetheless — you’ll just have to trust me Yeah, PowerShell is starting to drive me crazy again.

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• A question about PowerShell Module Manifests (huddledmasses.org)
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Shay Levy, ScriptFanatic, wrote about the PowerShellHostVersion on his blog this morning, explaining how it is not a field you should use in your module manifests.

Of course, there’s an exception: if your module is dependent on a specific host. For instance, if you’ve written a module for PoshConsole which exploits the WpfHost display features or the BgHost hotkeys feature … or if you’ve written ISEPack based on the menu and script-editor features of PowerShell ISE), then it makes sense to specify the PowerShellHostName and the PowerShellHostVersion together. However, if you aren’t taking a dependency on a specific host … you should definitely never specify PowerShellHostVersion by itself.

RequiredModules

I’ve got another one that I think you should not use. PowerShell has several ways of specifying prerequisites for your modules, such as assemblies that should be loaded, modules that must be nested, etc. In every case except RequiredModules, PowerShell will actually import those things for you.

That is, if you specify that you RequiredAssemblies = “System.Windows.Forms” it will automatically load it. If you specify NestedModules = “BitsTransfer” it will automatically load that. But if you specify RequiredModules = “BitsTransfer” you’re sore out of luck.

Not only does PowerShell not load them for you, it doesn’t give you all the information you need to load them when it fails. For example, consider that you have a module called “ReallyRequired” and one called “TestModule” which requires ReallyRequired. It’s metadata file is very simple, it looks like this:

Before we try to import it, we might try to check which modules it requires, and since it doesn’t appear to require any, we’ll go ahead and import it:

Apparently, there’s just no way to tell which module(s) you need to preload (or even whether there are any) until you get an error message. You might think you could just write a script to test for that error and then run Import-Module ReallyRequired … but what you don’t know is that after you load your copy of the ReallyRequired module:

If you’re like me, right now you’re tearing out your hair wondering why the error message didn’t tell you that in the first place. Then you have to go off and try to find a newer version of your RequiredModules. And that’s not even the crazy thing! The crazy thing is, if you find the wrong one, you could still get a message about the GUID not matching next.

So yeah, RequiredModules is really unlikely to be helpful right now. You’re better off just putting an Import-Module ReallyRequired -version 2.5 -ErrorAction Stop at the top of you script module (although that won’t help you if you’re writing a binary cmdlet module).

Some good news

This is just one of the things that the new PoshCode is being designed to address, so I’ll be blogging more about this shortly, but for now, you can use this function to list RequiredModules:

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• A question about PowerShell Module Manifests (huddledmasses.org)

So, I’m building the next PoshCode around modules, with CPAN as my model …

Scripts are still there, but they’re still basically done the way they are now: you just upload a single file.

Modules, however, will be treated specially. You’ll have to have an account to upload, but you’ll be able to just upload a .zip file of your module folder using your login and not fill in any other forms. Our system will take care of parsing the metadata out of the manifest in your module folder.

The problem is that I need a little data that isn’t a part of the standard module manifest format… and I can’t add it because PowerShell won’t load a module with extra fields in the manifest metadata hashtable: https://connect.microsoft.com/PowerShell/feedback/ViewFeedback.aspx?FeedbackID=421837 — My request was closed “by design” early in the beta cycle and I wasn’t able to convince them to rethink that.

At a minimum, PoshCode requires a LICENSE field, and a CATEGORY field (think of the categories on CPAN or TechNet Script Center).

So I’m having an informal poll. (you’ll have to “vote” by commenting or tweeting to me, because I want more than just “I choose A”).

Which option do you prefer, or can you think of a better way:

Require the License and Category to be part of the PRIVATEDATA field in the standard manifest

This might require authors to rewrite parts of their modules, because we’d be forcing PrivateData to be a Hashtable, and to contain keys that they don’t need in the module.

Some existing modules use an array in PrivateData, or even a simple string, rather than a Hashtable. However, it’s not a huge difference, and might be the cleanest method: it wouldn’t require you to manage a second file of data, and the additional data will be easily available to users and scripts via the standard Get-Module output.

Add a “doc comment” system for Module manifest files.

The upside of this is that PoshCode wants to create module-level documentation anyway. If we use documentation comments like those used on functions we would be able to just create our own standard for them, and add any extra fields we need. It would be guaranteed not to conflict with anything you’re already doing, and in addition to missing metadata, you could have some module-level documentation beyond just the Description field of the metadata.

The problem with this is that there’s no built-in way to parse that, and doing so isn’t trivial, so you would need to just read it on our website, or read the source of the file, or have our PoshCode cmdlets in order to make any sense of it once you had a module on your system. It doesn’t integrate with PowerShell in any meaningful way.

Embed the extra data right in the manifest hashtable, using a special comment to hide it from Get-Module

@{
author=“Joel Bennett”
description=“My latest crazy module”
<#!PoshCode
License=“Ms-PL”
Category=“WPF”,“GUI”,“Toolkit” #>
CompanyName=“Huddled Masses”
...
}


I like this because it’s fairly trivial for us to strip out the comment and just turn that into a plain-old DATA section. It also lends itself to reminding the PowerShell team that these fields are missing, and maintains the existing simple syntax of the manifest.

The problem here is, again, that the data doesn’t appear using any of the standard PowerShell tools — but getting it out is significantly easier than getting out document comments…

Require a separate “ReadMe.psd1” (or “PoshCode.pds1” or “Metadata.psd1”) metadata file

You could start with a copy of your module manifest, and then add the extra stuff that PoshCode needs. This would be nice because we would be able to add any extra fields we wanted as mandatory members, and we could include the “documentation” stuff I mentioned earlier…

But the downside is that it would be a third file (second manifest) that authors would have to maintain and keep current.

Any thoughts? Suggestions?

I’ve put some further thoughts about CPAN and the data problem on the wiki.

I’ve just created PowerShellGroup.org — a new site for PowerShell user groups (starting with: Rochester, Syracuse, Atlanta, Ottawa and of course, the Virtual Group).

It’s open to any PowerShell user groups or script clubs. If you’re running a PowerShell user group and want simple web-hosting with:

• top-of-the-site billing for your group (with a url like http://powershellgroup.org/rochester-ny )
• group signups
• events, calendars and event signups (including sending out RSVP emails to your group), and email reminders of events
• a semi-private group section for posting notices, wiki pages, etc.

• optional twitter notification for your posts

Just let me know who you are after you sign up on the site, and I can set you up with “group administrator” rights.

Also, if you have your own web hosting for your user group, but would like to be listed on our site, we can handle that too

This is old news and new news … but I figured it’s about time I break it on my blog, since it was mostly my doing (and since my Northeast Developer Evangelist Jim O’Neil already mentioned it on his blog).

We have created an official Virtual PowerShell Group (official, in the sense that it’s recognized by Microsoft’s User Group Support Services out of the unofficial #PowerShell channel on irc.freenode.net and have created a website to support it including a page where you can join us online via web-based chat any time you like.

Of course, this isn’t exactly headline news: The #PowerShell IRC channel has been around for years and has always been helpful and polite. What’s new is that we are officially a User Group, and have swag to give away (more on that later)! We’re hoping that this will help some of you justify joining us, and using IRC as a resource for your PowerShell learning and for those sticky questions!