Add ToRegex method to WildcardPattern class by yotsuda · Pull Request #26515 · PowerShell/PowerShell

yotsuda · 2025-11-23T11:25:07Z

PR Summary

Add public ToRegex() method to WildcardPattern class for converting PowerShell wildcard patterns to regular expressions.

PR Context

Resolves #19992

PowerShell users often need to convert wildcard patterns to regular expressions for use in programs that accept regex. While the internal implementation already exists, it was not accessible through a public API.

This PR exposes the conversion functionality by adding a public ToRegex() method to the WildcardPattern class.

Usage Example

$pattern = [System.Management.Automation.WildcardPattern]::new("*.txt")
$regex = $pattern.ToRegex()
$regexObj = [regex]::new($regex)
$regexObj.IsMatch("file.txt")  # True

Conversion Rules

* (asterisk) converts to .* in regex (matches zero or more characters)
? (question mark) converts to . (matches exactly one character)
[abc], [a-z] (bracket expressions) preserve their regex meaning (character sets and ranges)
Literal characters are escaped as needed (e.g., . → \.)
For backward compatibility, some optimizations are applied (e.g., standalone * returns empty string)

PR Checklist

PR has a meaningful title
Summarized changes
Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
This PR is ready to merge and is not Work in Progress
Breaking changes
- None
User-facing changes
- Documentation needed
  - Issue filed:
Testing - New and feature
- Make sure you've added a new test if existing tests do not effectively test the code changed
New and old tests pass locally

Description

Implementation

Added a public ToRegex() method to the WildcardPattern class that:

Leverages the existing internal PatternConvertedToRegex property
Returns a string (not Regex object) for maximum flexibility
Respects all WildcardOptions (IgnoreCase, CultureInvariant, Compiled)
Includes comprehensive XML documentation with examples

Files Changed

src/System.Management.Automation/engine/regex.cs - Added public ToRegex() method
test/powershell/engine/WildcardPattern.Tests.ps1 - Added comprehensive test coverage (13 tests)

Testing

Added Pester tests covering:

Basic wildcard conversions (*, ?, [])
WildcardOptions handling (IgnoreCase, CultureInvariant)
Consistency with WildcardPattern.IsMatch() behavior
Edge cases (empty pattern, escaped characters, standalone *)
Complex patterns (multiple wildcards, character ranges)

All 13 tests pass locally.

Additional Notes

Pure addition - no breaking changes
Uses existing optimized conversion logic
Enables interoperability between PowerShell wildcards and regex-based tools

- Add public ToRegex() method to convert wildcard patterns to regex - Leverage existing internal PatternConvertedToRegex property - Include comprehensive XML documentation with examples - Add 13 Pester tests covering various scenarios

Copilot

Pull request overview

This PR adds a public ToRegex() method to the WildcardPattern class, exposing existing internal wildcard-to-regex conversion functionality. This enables PowerShell users to convert wildcard patterns to regular expressions for use with regex-based tools and APIs.

Key changes:

Added public ToRegex() method that returns the regex string representation of the wildcard pattern
Included comprehensive XML documentation with conversion rules and usage examples
Added 13 Pester tests covering basic conversions, edge cases, wildcard options, and pattern matching consistency

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/System.Management.Automation/engine/regex.cs	Added public `ToRegex()` method with XML documentation to expose internal pattern conversion
test/powershell/engine/WildcardPattern.Tests.ps1	New test file with comprehensive test coverage for the ToRegex() method including basic conversions, options, edge cases, and complex patterns

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Address Copilot review feedback: - Use -BeExactly instead of -Match for precise regex validation - Fix question mark test: ? converts to . (single char), not .* - Fix escaped wildcard test: use single quotes to preserve backtick - Add clarifying comments for test intentions

Address review feedback to check exactly expected strings in all tests instead of using -Match assertions.

Add tests for trailing .*$ and both-end optimization

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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iSazonov · 2025-12-04T03:37:05Z

@daxian-dbw @SeeminglyScience Looking as the new method could be used should it return Regex type instead of string? I'd expect users want exactly get and use Regex and they will be forced to convert the string back to Regex. They can always call ToString() method themselves if necessary, for example, for debugging.

MatejKafka · 2025-12-04T16:36:56Z

+        /// </example>
+        public string ToRegex()
+        {
+            return PatternConvertedToRegex;


I'd somewhat expect a method called ToRegex() to return a Regex, not a string. Is there a good set of flags to set on Regex to reliably match what the pattern does? If so, I think it would be cleaner to return a pre-configured Regex instance so that the user is guaranteed to get exactly the same behavior.

iSazonov · 2025-12-06T04:50:22Z

@yotsuda I think the method should return Regex. Could you please make the change? Already added tests are good in the case too.

yotsuda · 2025-12-06T06:52:45Z

@iSazonov @MatejKafka Thanks for the feedback!

I've updated ToRegex() to return Regex instead of string. The implementation now caches the Regex instance for subsequent calls.

Changes (ce1dcf3):

ToRegex() returns Regex directly
Added _regex field to cache the instance
Removed the internal PatternConvertedToRegex property (was only used by ToRegex())
Added a test to verify that calling ToRegex() multiple times returns the same instance

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

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iSazonov · 2025-12-07T05:05:31Z

        private Predicate<string> _isMatch;

+        // cached regex for ToRegex() method
+        private Regex _regex;


Do we really need the cache? For example ToWql() doesn't use cache.
I believe the cache is needed only for multiple retrieves in high performance scenarios, but it is not our case.

Thanks for the review! I've removed the cache as you suggested. (793b74e)

Add ToRegex method to WildcardPattern class

16c9b9a

- Add public ToRegex() method to convert wildcard patterns to regex - Leverage existing internal PatternConvertedToRegex property - Include comprehensive XML documentation with examples - Add 13 Pester tests covering various scenarios

iSazonov added the CL-General Indicates that a PR should be marked as a general cmdlet change in the Change Log label Nov 24, 2025

iSazonov requested a review from Copilot November 24, 2025 05:06

Copilot started reviewing on behalf of iSazonov November 24, 2025 05:07 View session

Copilot finished reviewing on behalf of iSazonov November 24, 2025 05:09

Copilot AI reviewed Nov 24, 2025

View reviewed changes

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1 Outdated

Comment thread src/System.Management.Automation/engine/regex.cs Outdated

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1 Outdated

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1 Outdated

yotsuda and others added 2 commits November 24, 2025 15:52

Update src/System.Management.Automation/engine/regex.cs

69b26ce

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

iSazonov reviewed Nov 24, 2025

View reviewed changes

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1 Outdated

Use exact string assertions in ToRegex tests

f2355ed

Address review feedback to check exactly expected strings in all tests instead of using -Match assertions.

iSazonov reviewed Nov 24, 2025

View reviewed changes

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1 Outdated

Remove tests that only verify standard Regex behavior

7ff9e16

Add tests for trailing .*$ and both-end optimization

iSazonov reviewed Nov 25, 2025

View reviewed changes

Comment thread src/System.Management.Automation/engine/regex.cs Outdated

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1 Outdated

Address review feedback: terminology and test format

6b86171

iSazonov reviewed Nov 26, 2025

View reviewed changes

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1 Outdated

Add tests for all escaped wildcard characters (PowerShell#19992)

f6e9ddc

iSazonov requested a review from Copilot November 26, 2025 04:51

Copilot started reviewing on behalf of iSazonov November 26, 2025 04:52 View session

Copilot finished reviewing on behalf of iSazonov November 26, 2025 04:54

Copilot AI reviewed Nov 26, 2025

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microsoft-github-policy-service Bot added the Review - Needed The PR is being reviewed label Dec 3, 2025

microsoft-github-policy-service Bot removed the Review - Needed The PR is being reviewed label Dec 4, 2025

MatejKafka reviewed Dec 4, 2025

View reviewed changes

Change ToRegex() to return Regex instead of string

ce1dcf3

iSazonov requested a review from Copilot December 6, 2025 18:27

Copilot started reviewing on behalf of iSazonov December 6, 2025 18:27 View session

Copilot AI reviewed Dec 6, 2025

View reviewed changes

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1

Comment thread src/System.Management.Automation/engine/regex.cs Outdated

Comment thread test/powershell/engine/WildcardPattern.Tests.ps1 Outdated

Add RegexOptions verification and fix documentation example

7a8fbb1

iSazonov reviewed Dec 7, 2025

View reviewed changes

Remove ToRegex caching for consistency with ToWql

793b74e

iSazonov approved these changes Dec 7, 2025

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iSazonov self-assigned this Dec 10, 2025

iSazonov merged commit 7f92d58 into PowerShell:master Dec 10, 2025
44 of 46 checks passed

yotsuda deleted the feature/issue-19992-wildcard-toregex branch December 10, 2025 21:46

SIRMARGIN pushed a commit to SIRMARGIN/PowerShell that referenced this pull request Dec 12, 2025

Add ToRegex method to WildcardPattern class (PowerShell#26515)

54b7586

kilasuit pushed a commit to kilasuit/PowerShell that referenced this pull request Jan 2, 2026

Add ToRegex method to WildcardPattern class (PowerShell#26515)

41d336b

Conversation

yotsuda commented Nov 23, 2025

PR Summary

PR Context

Usage Example

Conversion Rules

PR Checklist

Description

Implementation

Files Changed

Testing

Additional Notes

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iSazonov commented Dec 4, 2025

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iSazonov commented Dec 6, 2025

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