string and RegExp are not logically consistent

[xiexiaobo135]

Which @angular/* package(s) are the source of the bug?

forms

Is this a regression?

No

Description

angular/packages/forms/src/validators.ts

Line 534 in 0d65e1d

export function patternValidator(pattern: string|RegExp): ValidatorFn {

Hello~

let test1 = "\\d{2}";
let test2 = /\d{2}/;  // or new RegExp(test1)
...
Validators.pattern(test1);
// !==, without ^ and $ ??? Do string and RegExp need to be consistent?
Validators.pattern(test2);

Please provide a link to a minimal reproduction of the bug

angular/packages/forms/src/validators.ts

Line 548 in 0d65e1d

} else {

Please provide the exception or error you saw

No response

Please provide the environment you discovered this bug in (run ng version)

Angular CLI: 14.2.6
Node: 16.14.2
Package Manager: npm 8.19.2
OS: win32 x64

Angular: 14.2.6
... animations, cli, common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1402.6
@angular-devkit/build-angular   14.2.6
@angular-devkit/core            14.2.6
@angular-devkit/schematics      14.2.6
@schematics/angular             14.2.6
rxjs                            7.5.7
typescript                      4.7.4

Anything else?

No response

[JoostK]

This is working as documented:

angular/packages/forms/src/validators.ts

Lines 381 to 384 in 4e46370

	* @param pattern A regular expression to be used as is to test the values, or a string.
	* If a string is passed, the `^` character is prepended and the `$` character is
	* appended to the provided string (if not already present), and the resulting regular
	* expression is used to test the values.

Regex support was requested in #10150 and implemented in #12323 precisely to differentiate between the ^ and $ prefix/suffix that would otherwise get added automatically for strings, as mirrored from the HTML5 pattern validation attribute for inputs. Described on MDN as follows:

The pattern's regular expression, when matched against the value, must have its start anchored to the start of the string and its end anchored to the end of the string, which is slightly different from JavaScript regular expressions: in the case of pattern attribute, we are matching against the entire value, not just any subset, as if a ^(?: were implied at the start of the pattern and )$ at the end.

So yes, the difference is intentional.

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