More useful var templating errors

[Vladimir-csp]

Summary

When a templated var fails due to error in template, the error message is unhelpful and hard to read. It consists of:

• A message An unhandled exception occured while templating
• Literal representation of template
• The actual error message, i.e. Error was a class 'ansible.errors.AnsibleError'>, original message: template error while templating string: expected an expression, got 'end of statement block. String:
• Another literal representation of template.

No indication where in the template (row, column) the error has occured. Also it is hard hard to find the actual template error between two redundant printings of the same template.

The feature request is: show the actual template error text, then info on location of the error, and only then a single printing of the template, maybe with the error position marked as it is with yaml errors.

Issue Type

Feature Idea

Component Name

template

Additional Information

Current error message:

fatal: [hostname]: FAILED! => 
  msg: |-
    An unhandled exception occurred while templating '{# lots #}
    {# and lots #}
    {# and lots #)
    {# and lots #}
    {# and lots of template text #}'. Error was a <class 'ansible.errors.AnsibleError'>, original message: template error while templating string: Unexpected ')', expected '}'. String: {# lots #}
    {# and lots #}
    {# and lots #)
    {# and lots #}
    {# and lots of template text #}

Suggested:

fatal: [hostname]: FAILED! => 
  msg: |-
    template error while templating string: Unexpected ')', expected '}'. Line 3, Col 14, String: 
    {# lots #}
    {# and lots #}
    {# and lots #)
                 ^ here
    {# and lots #}
    {# and lots of template text #}

Code of Conduct

• I agree to follow the Ansible Code of Conduct

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Files identified in the description:
None

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[ansibot]

Files identified in the description:

• lib/ansible/modules/template.py

If these files are incorrect, please update the component name section of the description or use the !component bot command.

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