Allow RegularExpression for path match be RE2/PCRE friendly. #4450

salonichf5 · 2025-12-11T21:04:16Z

Proposed changes

Write a clear and concise description that helps reviewers understand the purpose and impact of your changes. Use the
following format:

Problem: Users had trouble specifying the PCRE style regex expressions when migrating from nginx-ingress

Solution: Use regexp2 to validate regular expression which is Perl5 library and ensure it is PCRE and RE2 friendly to avoid any breaking changes.

Testing: Manual testing, unit tests.

Testing with regular expressions from customer issues

cafe-route.yaml

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: coffee
spec:
  parentRefs:
  - name: cafe
  hostnames:
  - cafe.example.com
  rules:
  - matches:
    - path:
        type: RegularExpression
        value: /(service\/(?!private/).*) --> does not allow /service/private
    backendRefs:
    - name: coffee-v1-svc
      port: 80
  - matches:
    - path:
        type: RegularExpression
        value: /rest/.*/V1/order/get/.*
      headers:
      - name: headerRegex
        type: RegularExpression
        value: "header-[a-z]{1}"
    - path:
        type: RegularExpression
        value: /rest/.*/V1/order/get/.*
      queryParams:
      - name: queryRegex
        type: RegularExpression
        value: "query-[a-z]{1}"
    backendRefs:
    - name: coffee-v3-svc
      port: 80

config

server {
    listen 80;
    listen [::]:80;

    server_name cafe.example.com;
       location ~ /(service\/(?!private/).*) {
        proxy_pass http://default_coffee-v1-svc_80$request_uri;
    }
    location ~ /rest/.*/V1/order/get/.* {
       set $match_key 1_1;
        js_content httpmatches.redirect;
    }
    location /_ngf-internal-rule1-route0 {
        internal;
        proxy_pass http://default_coffee-v3-svc_80$request_uri;
    }
    location /_ngf-internal-rule1-route1 {
        internal;
        proxy_pass http://default_coffee-v3-svc_80$request_uri;
    }
}

curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/service/private/hello
Handling connection for 8080
<html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>nginx</center>
</body>
</html>

sa.choudhary@N9939CQ4P0 nginx-gateway-fabric % curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/service/private/server
Handling connection for 8080
<html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>nginx</center>
</body>
</html>

curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/service/coffee
Handling connection for 8080
Server address: 10.244.0.149:8080
Server name: coffee-v1-55fcb4c6b7-k6qld
Date: 11/Dec/2025:20:54:47 +0000
URI: /service/coffee
Request ID: d69503b10ac9d5e37568b8efa5d5b4fd

regex with query params and headers regex -- multiple matches

sa.choudhary@N9939CQ4P0 nginx-gateway-fabric % curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/rest/example/V1/order/get/customer\?queryRegex\=query-a
Handling connection for 8080
Server address: 10.244.0.151:8080
Server name: coffee-v3-5f7d4f6f47-vzpb8
Date: 11/Dec/2025:21:02:00 +0000
URI: /rest/example/V1/order/get/customer?queryRegex=query-a
Request ID: 1800b9049d08da54ec8c7cbcd316308d


sa.choudhary@N9939CQ4P0 nginx-gateway-fabric % curl --resolve cafe.example.com:$GW_PORT:$GW_IP -H "headerRegex: header-a" http://cafe.example.com:$GW_PORT/rest/example/V1/order/get/lists
Handling connection for 8080
Server address: 10.244.0.151:8080
Server name: coffee-v3-5f7d4f6f47-vzpb8
Date: 11/Dec/2025:21:02:50 +0000
URI: /rest/example/V1/order/get/lists
Request ID: f65e504c759ba42b5fda75dfab1cc853

Please focus on (optional): If you any specific areas where you would like reviewers to focus their attention or provide
specific feedback, add them here.

Closes #4409

Checklist

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I have read the CONTRIBUTING doc
I have added tests that prove my fix is effective or that my feature works
I have checked that all unit tests pass after adding my changes
I have updated necessary documentation
I have rebased my branch onto main
I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

Updated validation for pathType RegularExpression to support PCRE-style patterns while remaining RE2-friendly, improving compatibility with other projects.

Copilot

Pull request overview

This PR updates the regular expression validation for pathType: RegularExpression to support PCRE-style patterns while maintaining RE2 compatibility, addressing user migration issues from nginx-ingress. The implementation switches from Go's standard regexp package to the regexp2 library, which provides Perl5-compatible regex support with RE2 compatibility mode.

Key Changes:

Replaced restrictive RE2-only validation with regexp2-based validation supporting PCRE patterns
Removed explicit bans on backreferences, lookarounds, and unescaped $ characters
Expanded test coverage to include PCRE-style patterns like named groups, lookaheads, and backreferences

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
`go.mod`	Added `github.com/dlclark/regexp2 v1.11.5` dependency for Perl5-compatible regex support
`internal/controller/nginx/config/validation/common.go`	Replaced `regexp.Regexp` with `regexp2.Regexp`, simplified validation logic by removing RE2-specific restrictions, updated documentation
`internal/controller/nginx/config/validation/common_test.go`	Expanded valid test cases to include PCRE patterns (lookaheads, backreferences, variable-width lookbehinds), removed previously-forbidden patterns from invalid test cases, added inline comments explaining test cases

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internal/controller/nginx/config/validation/common_test.go

codecov · 2025-12-11T21:09:12Z

Codecov Report

❌ Patch coverage is 30.76923% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.05%. Comparing base (932f9aa) to head (a793dfb).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ernal/controller/nginx/config/validation/common.go	30.76%	3 Missing and 6 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4450   +/-   ##
=======================================
  Coverage   86.05%   86.05%           
=======================================
  Files         132      132           
  Lines       14389    14382    -7     
  Branches       35       35           
=======================================
- Hits        12383    12377    -6     
+ Misses       1795     1791    -4     
- Partials      211      214    +3

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Pull request overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated 3 comments.

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internal/controller/nginx/config/validation/common_test.go

internal/controller/nginx/config/validation/common.go

bjee19

nice job

salonichf5 requested a review from a team as a code owner December 11, 2025 21:04

github-project-automation bot added this to NGINX Gateway Fabric Dec 11, 2025

nginx-bot bot added the release-notes label Dec 11, 2025

github-project-automation bot moved this to 🆕 New in NGINX Gateway Fabric Dec 11, 2025

salonichf5 requested a review from Copilot December 11, 2025 21:04

github-actions bot added enhancement New feature or request dependencies Pull requests that update a dependency file labels Dec 11, 2025

Copilot AI reviewed Dec 11, 2025

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internal/controller/nginx/config/validation/common_test.go Show resolved Hide resolved

update regexp2 for path match check

440ae67

sjberman approved these changes Dec 11, 2025

View reviewed changes

salonichf5 force-pushed the feat/update-regex-pkg branch from c591e11 to 440ae67 Compare December 11, 2025 21:11

salonichf5 requested a review from Copilot December 11, 2025 21:12

Copilot AI reviewed Dec 11, 2025

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internal/controller/nginx/config/validation/common_test.go Show resolved Hide resolved

internal/controller/nginx/config/validation/common_test.go Show resolved Hide resolved

internal/controller/nginx/config/validation/common.go Show resolved Hide resolved

add unit tests for regex

f61b4fc

bjee19 approved these changes Dec 11, 2025

View reviewed changes

Merge branch 'main' into feat/update-regex-pkg

a793dfb

salonichf5 enabled auto-merge (squash) December 11, 2025 21:43

salonichf5 merged commit f536ed9 into main Dec 11, 2025
59 of 61 checks passed

salonichf5 deleted the feat/update-regex-pkg branch December 11, 2025 22:09

github-project-automation bot moved this from 🆕 New to ✅ Done in NGINX Gateway Fabric Dec 11, 2025

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Allow RegularExpression for path match be RE2/PCRE friendly. #4450

Allow RegularExpression for path match be RE2/PCRE friendly. #4450

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Allow RegularExpression for path match be RE2/PCRE friendly. #4450

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salonichf5 commented Dec 11, 2025

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