[BUG] [typescript-angular] pattern data gets improperly escaped

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

This issue has been raised and fixed years ago for the typescript-axios client:

• BUG: #5973
• PR: #5974

I feel like the problem it is sufficiently described, so not adding any more details here.

Example:

• {{{pattern}}} is /^(0|[1-9]\\d*)\\.(0|[1-9]\\d*)\\.(0|[1-9]\\d*)$/
• {{{pattern}}} should be /^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)$/

openapi-generator version

• LATEST

Steps to reproduce

1. Include this pattern in your OpenAPI spec

   {
       "pattern": "^(0|[1-9]\\d*)\\.(0|[1-9]\\d*)\\.(0|[1-9]\\d*)$",
   }
   

2. Run the typescript-angular generator

   • NOTE: That the out of the box templates do NOT use the pattern field. For my needs I have adjusted the mustache templates to include them. So to reproduce you might have to do the same.

3. Actual vs. Expected output:

• {{{pattern}}} is /^(0|[1-9]\\d*)\\.(0|[1-9]\\d*)\\.(0|[1-9]\\d*)$/
• {{{pattern}}} should be /^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)$/

Related issues/PRs

• #5973
• #5974

Suggest a fix

Two options here:

1. A patch for typescript-angular only
   • Apply the same patch that was done for typescript-axios and override the toRegularExpression method in TypeScriptAngularClientCodegen.java
2. A full fix for all typescript based client (as all typescript generators will eventually face the same problem)
   • Override the toRegularExpression method in the AbstractTypeScriptClientCodegen.java abstract base class.

The implementation will be the same regardless of the option choosen (just the location would change). Here is that code:

    /**
     * Overriding toRegularExpression() to avoid escapeText() being called,
     * as it would return a broken regular expression if any escaped character / metacharacter were present.
     */
    @Override
    public String toRegularExpression(String pattern) {
        return addRegularExpressionDelimiter(pattern);
    }

Start by comparing the existing typescript-axios fix in PR #5974 with TypeScriptAngularClientCodegen.java and AbstractTypeScriptClientCodegen.java. Reproduce the issue with the OpenAPI pattern shown and the typescript-angular generator; done means generated pattern data retains the intended backslashes without improper escaping.