Escaping special characters in regex_replace with '\' fails with: unknown escape character

[jean-christophe manciot]

ansible: 2.10.5 (with pip3 install)

python version = 3.9.1+ (default, Jan 20 2021, 14:49:22) [GCC 10.2.1 20210110]

Escaping special characters in the searched string such as the following should be simply done with '\':

- ' --> \'

- ( --> \(

- , --> \,

- ) --> \)

However, it seems to be impossible to perform this task with a single '\' or even a double '\\'; for instance, running the following playbook fails:

```

---

- name: Escaping special characters in regex_replace fails

  hosts:

        - localhost

  strategy: debug

  vars:

        searched_string: "('string_a', 'string_b'),('string_c', 'string_d')"

  tasks:

        - name: Escaping with '\' - Result expected is "string_a@string_b,string_c@string_d"

          set_fact:

                replaced_string: "{{ searched_string |

                                     regex_replace('\(\'([^\']+)\'\, \'([^\']+)\'\)', '\\1@\\2') }}"

...

```

leads to:

```

ERROR! We were unable to read either as JSON nor YAML, these are the errors we got from each:

JSON: Expecting value: line 1 column 1 (char 0)

Syntax Error while loading YAML.

  found unknown escape character

The error appears to be in 'escape_special_characters_in_regex_replace.yml': line 16, column 53, but may

be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:

                replaced_string: "{{ searched_string |

                                     regex_replace('\(\'([^\']+)\'\, \'([^\']+)\'\)', '\\1@\\2') }}"

                                                    ^ here

```

I thought about using the jinja2 'replace' filter to remove all special characters first, but that would just be throwing the can down the road, right? ;-)

What am I missing?

[jean-christophe manciot]

I meant kicking ...., but you got the idea.

[Felix Fontein]

Hi,

the problem is that you're inside a YAML " " string, which already
interprets escaping.

Try using `>-` or something like that (https://yaml-multiline.info/)
instead of double quotes for the string that's templated, like

replaced_string: >-

{{ searched_string | regex_replace(
'\(\'([^\']+)\'\, \'([^\']+)\'\)', '\\1@\\2') }}

Then it should work.

(Alternatively, if you use " ", you need to double escape - which is
extremely ugly to read.)

Cheers,
Felix




On Wed, 3 Feb 2021 10:49:44 -0800 (PST)
jean-christophe manciot <actionm...@gmail.com> wrote:

> ansible: *2.10.5* (with pip3 install)

[Vladimir Botka]

On Wed, 3 Feb 2021 10:49:44 -0800 (PST)
jean-christophe manciot <actionm...@gmail.com> wrote:

> vars:
> searched_string: "('string_a', 'string_b'),('string_c', 'string_d')"

> ...
> Result expected is "string_a@string_b,string_c@string_d"
> ...

> set_fact:
> replaced_string: "{{ searched_string |
> regex_replace('\(\'([^\']+)\'\,
> \'([^\']+)\'\)', '\\1@\\2') }}"

FWIW, create lists and join the items

- set_fact:
replaced_string: "{{ searched_lists|
map('join', '@')|list|
join(',') }}"
vars:
pleft: '\('
pright: '\)'
bleft: '['
bright: ']'
searched_lists: "{{ searched_string|
regex_replace(pleft, bleft)|
regex_replace(pright, bright) }}"

--
Vladimir Botka

[Vladimir Botka]

This simplified version gives the same result

- set_fact:
replaced_string: "{{ searched_lists|
map('join', '@')|list|
join(',') }}"
vars:

searched_lists: "{{ '[' ~ searched_string ~ ']' }}"


--
Vladimir Botka

[jean-christophe manciot]

@Felix Fontein

I tried to replace the double-quotes with:

-  >-: "An unhandled exception occurred while templating"

- '>: "An unhandled exception occurred while templating"

@Vladimir Botka

Fantastic :-)

I chose the last version.