Routing exception after upgrading to TYPO3 v9.5.14 - typo3

Question

After upgrading to TYPO3 v9.5.14 our detail pages for news crash with the exception
Symfony\Component\Routing\Exception\InvalidParameterException
Parameter "p88bd715a41119d0e8087a5d19cb049" for route "tx_news_pi1_1" must match "[^/]++" ("" given) to generate a corresponding URL.
What's going on?
The site used this configuration:
NewsTagPlugin:
type: Extbase
limitToPages: [14]
extension: News
plugin: Pi1
routes:
- routePath: '/{tag-name}'
_controller: 'News::list'
_arguments:
tag-name: 'overwriteDemand/tags'
- routePath: '/{tag-name}/page/{page}'
_controller: 'News::list'
_arguments:
tag-name: 'overwriteDemand/tags'
page: '#widget_0/currentPage'
requirements:
page: '\d+'
defaultController: 'News::list'
defaults:
page: ''
aspects:
page:
type: IntegerMapper
start: 1
end: 5000
tag-name:
type: PersistedAliasMapper
tableName: tx_news_domain_model_tag
routeFieldName: slug

Answer 1

1) Superfluous mapping
NewsTagPlugin:
...
routes:
...
- routePath: '/{tag-name}/page/{page}'
_controller: 'News::list'
_arguments:
tag-name: 'overwriteDemand/tags'
page: '#widget_0/currentPage'
requirements:
page: '\d+'
_arguments defines a mapping for route parameter and internal variables (e.g. as query parameter`
requirements is wrong here, since it shall not be used as argument mapping
parameter requirements need to be defined on the root level of NewsTagPlugin
2) Invalid empty default value
NewsTagPlugin:
...
routes:
...
- routePath: '/{tag-name}/page/{page}'
...
defaults:
page: ''
aspects:
...
defaults was not applied prior to TYPO3 v9.5.14 and addressed in https://review.typo3.org/c/Packages/TYPO3.CMS/+/60361
the empty default value for parameter page does not make much sense and would lead to an URL like /some-tag/page/ which is causing the error message shown in the answer
the default value should be page: 1
in case the parameter should be omitted in the URL (e.g. having /some-tag/page/) this needs to be defined explicitly using {!page} in the route path
References
https://symfony.com/doc/4.3/routing.html#optional-parameters
https://docs.typo3.org/c/typo3/cms-core/master/en-us/Changelog/9.5.x/Important-86895-RouteAspectsTakePrecedenceOverRequirements.html
Adjusted enhancer configuration
NewsTagPlugin:
type: Extbase
limitToPages: [14]
extension: News
plugin: Pi1
routes:
- routePath: '/{tag-name}'
_controller: 'News::list'
_arguments:
tag-name: 'overwriteDemand/tags'
- routePath: '/{tag-name}/page/{!page}'
_controller: 'News::list'
_arguments:
tag-name: 'overwriteDemand/tags'
page: '#widget_0/currentPage'
defaultController: 'News::list'
defaults:
page: 1
aspects:
page:
type: IntegerMapper
start: 1
end: 5000
tag-name:
type: PersistedAliasMapper
tableName: tx_news_domain_model_tag
routeFieldName: slug
(untested) since IntegerMapper seems to be a custom aspect implementation - not being available to the public

Answer 2

First off, consider https://docs.typo3.org/c/typo3/cms-core/master/en-us/Changelog/9.5.x/Important-86895-RouteAspectsTakePrecedenceOverRequirements.html
The culprit is the default configuration for the page aspect.
It was once introduced to make sure that the URL for the first tag page is always "/tag-name" and only subsequent pages have "/tag-name/page/2" and so on.
This default value now needs to be removed in order to have the requirements applied as desired.