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GeezerVison is showing github.com — Add AvoidReservedWordsAsFunctionNames Rule by liamjpeters · Pull Request #2128 · PowerShell/PSScriptAnalyzer

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Liam Peters (liamjpeters) commented Sep 1, 2025

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PR Summary

Adds a new rule that warns when reserved words are used as function names.

function function {}

function if {
    function else {}
}

function global:try {}

function private:catch {}

Fixes #2099

I wrote a blog post about putting this together 😀

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Change is not breaking
Make sure all .cs, .ps1 and .psm1 files have the correct copyright header
Make sure you've added a new test if existing tests do not effectively test the code changed and/or updated documentation
This PR is ready to merge and is not Work in Progress.
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Liam Peters (liamjpeters) requested review from Andy Jordan (andyleejordan), Christoph Bergmeister (bergmeister), Mikey Lombardi (He/Him) (michaeltlombardi) and Sean Wheeler (sdwheeler) as code owners

September 1, 2025 18:29

Liam Peters (liamjpeters) commented Sep 3, 2025 •

edited

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Just as a note...

I did attempt to use reflection rather than a hard-coded list of keywords. The keyword list is in the Tokenizer.

public static HashSet<string> GetReservedWordsFromTokenizer()
{
    // Get the assembly containing Tokenizer
    var asm = typeof(Token).Assembly;

    // Get the internal Tokenizer type
    var tokenizerType = asm.GetType("System.Management.Automation.Language.Tokenizer");

    // Get the private static readonly field s_keywordTokenKind
    var field = tokenizerType.GetField("s_keywordTokenKind", BindingFlags.NonPublic | BindingFlags.Static);

    // Get the TokenKind[] value
    var tokenKinds = field.GetValue(null) as Array;

    var reservedWords = new HashSet<string>(
        tokenKinds.Cast<Enum>().Select(tk => tk.ToString()),
        StringComparer.OrdinalIgnoreCase
    );

    return reservedWords;
}

With similar on the PowerShell side for the tests.

This worked fine in PS7 but I can't seem to get it to work in PS5.1 - I can't access the s_keywordTokenKind or s_keywordText field.

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Andy Jordan (andyleejordan) commented Oct 15, 2025

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This worked fine in PS7 but I can't seem to get it to work in PS5.1 - I can't access the s_keywordTokenKind or s_keywordText field.

That makes sense to me. We've run into similar issues in PSES because the visibility of some of them changed making them available through reflection in PS7 but still not in PS5.1. Oh well 🫠

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Liam Peters (liamjpeters) added 4 commits

October 15, 2025 16:23


          fix: Update helper GetScriptExtentForFunctionName to return correct e…

fbe1489

…xtent when function name is 'function'


          Add AvoidReservedWordsAsFunctionNames rule

b4f67c2


          fix: Handle functions with scopes

1819eb3


          Copyright header

1e5c1b2

Andy Jordan (andyleejordan) force-pushed the #2099PSAvoidReservedWordsAsFunctionNames branch from 6672621 to 1e5c1b2 Compare

October 15, 2025 23:23

Andy Jordan (andyleejordan) reviewed

Oct 15, 2025

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Patrick Meinecke (@SeeminglyScience) can you take a look at this too? Seems pretty good to me and reasonable to add as a default.

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Engine/Helper.cs Resolved

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Rules/AvoidReservedWordsAsFunctionNames.cs Resolved

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Rules/Strings.resx Resolved

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Tests/Engine/GetScriptAnalyzerRule.tests.ps1 Resolved

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Tests/Rules/AvoidReservedWordsAsFunctionNames.tests.ps1 Resolved

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Liam Peters (liamjpeters) and others added 3 commits

October 16, 2025 20:43


          Extend Substring tests to starts with reserved word, ends with reserv…

3b56a76

…ed word, and reserved word with a letter missing


          Check if the function name is 'Function' case insensitively. Add a te…

4510ff4

…st for good measure


          Fix casing of common name

a9e6182

Co-authored-by: Andy Jordan <[email protected]>

Andy Jordan (andyleejordan) approved these changes

Oct 20, 2025

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I'm good with this, just want Patrick Meinecke (@SeeminglyScience) to double check. I'll send it his way.

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Patrick Meinecke (SeeminglyScience) requested changes

Oct 21, 2025

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Definitely a useful rule, ty Liam! Couple of small changes

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Rules/AvoidReservedWordsAsFunctionNames.cs Resolved

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Rules/AvoidReservedWordsAsFunctionNames.cs Resolved

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Liam Peters (liamjpeters) and others added 2 commits

October 21, 2025 19:07


          AvoidReservedWordsAsFunctionNames: factor our function name for reada…

80172fe

…bility

Co-authored-by: Patrick Meinecke <[email protected]>


          Remove reserved words which do not pose an issue:

8f89a1b

assembly, base, command, hidden, in, inlinescript, interface,
module, namespace, private, public, static

Liam Peters (liamjpeters) commented Oct 21, 2025

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We did it, high-fives all round 🫸🫷

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Patrick Meinecke (SeeminglyScience) approved these changes

Oct 21, 2025

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LGTM!

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Andy Jordan (andyleejordan) enabled auto-merge (squash)

October 22, 2025 20:22

Mikey Lombardi (He/Him) (michaeltlombardi) approved these changes

Oct 22, 2025

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LGTM!

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Andy Jordan (andyleejordan) merged commit a9898a6 into PowerShell:main

Oct 22, 2025

Liam Peters (liamjpeters) deleted the #2099PSAvoidReservedWordsAsFunctionNames branch

October 23, 2025 22:17

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Mikey Lombardi (He/Him) (michaeltlombardi)

michaeltlombardi approved these changes

Patrick Meinecke (SeeminglyScience)

SeeminglyScience approved these changes

Sean Wheeler (sdwheeler)

Awaiting requested review from sdwheeler

Christoph Bergmeister (bergmeister)

Awaiting requested review from bergmeister

bergmeister is a code owner

+1 more reviewer

Andy Jordan (andyleejordan)

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Rule request: Avoid reserved words for functions names

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Liam Peters (liamjpeters) commented Sep 1, 2025

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Liam Peters (liamjpeters) commented Sep 3, 2025 •

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