Field.regex will allow an invalid string to pass validation

[kierandarcy]

Bug

The regex used to validate a string in pydantic.Field will allow a string that does not match the given pattern to pass without raising a validation error.

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.5.1
            pydantic compiled: True
                 install path: /home/kieran/projects/bimacademy/buildstream/prototypes/backend-admin/.venv/lib/python3.8/site-packages/pydantic
               python version: 3.8.2 (default, Feb 26 2020, 02:56:10)  [GCC 7.4.0]
                     platform: Linux-4.15.0-99-generic-x86_64-with-glibc2.27
     optional deps. installed: []

This simple regex checks for any number of lowercase letters ("a - z") and spaces.

In the example below, the test="this Should Fail" should raise a validation error. It does not. I think this is because it is using re.match instead if re.fullmatch.

import re
import pydantic

class Test(pydantic.BaseModel): 
    test: str = pydantic.Field(regex="[a-z ]+", description="Allow lower case letters and spaces")

try:
    Test(test="this should pass")
except pydantic.ValidationError:
    print("This should have passed!")

try:
    Test(test="this Should Fail")
except pydantic.ValidationError:
    print("This should have failed!")

assert bool(re.fullmatch("[a-z ]+", "this should pass"))
assert not bool(re.fullmatch("[a-z ]+", "this Should Fail"))

Happy to submit a PR! (Looks like a nice easy one)

[samuelcolvin]

Not a bug, duplicate of #1396.