311 lines
8.8 KiB
ReStructuredText
311 lines
8.8 KiB
ReStructuredText
Calculation with a jinja type
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===============================
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.. objectives:: Objectives
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In this section we will learn how to create new ways of calculation.
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Up to now, our only way of dynamically (that is, during the runtime) calculating
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a value is to point on another variable's value. But this is not the only way.
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.. todo:: on peut aussi faire un exercice de ce genre pour la propriété mandatory
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A jinja calculated variable's hidden property
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------------------------------------------------
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We can hide or disable some variables or families with other techniques than
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pointing on a variable's value.
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Let's reason on the previous HTTPS proxy configuration's manual mode:
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.. code-block:: yaml
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manual:
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use_for_https:
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description: Also use this proxy for HTTPS
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default: true
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https_proxy:
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type: family
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description: HTTPS Proxy
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hidden:
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variable: manual.use_for_https
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This is extracted from the proxy's manual configuration we discussed before.
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We see here that there is an `https_proxy` family that is going to be hidden
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depending on the value of another variable:
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.. code-block:: yaml
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https_proxy:
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type: family
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hidden:
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variable: manual.use_for_https
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Now we could write it like that:
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.. code-block:: yaml
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manual:
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use_for_https:
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description: Also use this proxy for HTTPS
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default: true
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https_proxy:
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description: HTTPS Proxy
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type: family
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hidden:
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type: jinja
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jinja: |
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{% if rougail.manual.use_for_https %}
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the HTTPS Proxy family is hidden
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{% endif %}
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Yes, it's done in a more complicated (but more powerful) way.
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Let's explain this a little:
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We have replaced this simple hidden property declaration:
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.. code-block:: yaml
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hidden:
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variable: manual.use_for_https
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by this (more complicated) hidden property declaration:
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.. code-block:: yaml
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hidden:
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type: jinja
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jinja: |
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{% if rougail.manual.use_for_https %}
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the HTTPS Proxy family is hidden
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{% endif %}
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The fact is that it has same result, but here we have more possibilities.
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The hidden process is done by a calculation.
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Another jinja calculation type sample
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---------------------------------------
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We can now hide or disable some variables or families with other techniques than
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pointing on a variable's value.
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Let's reason upon the proxy's manual configuration we discussed before.
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We have the :file:`dict/02-proxy_manual.yml` structure file:
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.. code-block:: yaml
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:caption: the :file:`structfile/02-proxy_manual.yml` file
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---
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version: '1.1'
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manual:
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description: Manual proxy configuration
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type: family
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disabled:
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type: jinja
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jinja: |
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{% if rougail.proxy.proxy_mode != 'Manual proxy configuration' %}
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the proxy mode is not manual
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{% endif %}
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.. questions:: Question
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**question**: OK then. What happens when you select the "Manual proxy configuration"?
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Here if the user selects the "Manual proxy configuration" proxy mode,
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the the `manual` family will be disabled. This is what the jinja code says.
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Let's explain it more precisely.
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.. note:: The "the proxy mode is not manual" output is be used in the log outputs
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for example while
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Why Jinja?
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---------------
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.. questions:: What about this `Jinja` type?
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If the :term:`Jinja` template returns some text, then the family will be `disabled`. Otherwise it is accessible.
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Deactivating a family means that we will not be able to access it as well as the variables or families included in this family.
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.. note:: If the Jinja template does not return any text, the variable will be **enabled**.
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Here we are using the Jinja condition statement.
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.. glossary::
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Jinja
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`Jinja <https://jinja.palletsprojects.com>`_ is a template engine.
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we are using Jinja in a classical way, that is, Jinja allows us to handle different cases,
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for example with the `if` statement.
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What can be calculated?
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---------------------------
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We have seen that the `disabled` or `hidden` properties could be calculated.
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The default values can be calculated too.
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.. todo:: montrer un exemple de valeur par défaut calculées (type jinja)
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.. todo:: montrer aussi ici des exemples de calculs de valeurs variables, ce qui est un des usages principaux de jinja
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Using jinja in a dynamic family declaration
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-----------------------------------------------
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Let's come back to the previous section's :ref:`dynamic family example <conditional_hidden_family>`\ .
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In a dynamic family, as seen before, you have the possibility to name your identifier. In the classic declaration,
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the identifier's variable is named "identifier" by default. Sounds logical:
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.. code-block:: yaml
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"{{ identifier }}_proxy":
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description: "{{ identifier }} Proxy"
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dynamic:
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- HTTPS
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- SOCKS
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Here the identifer's variable takes the value of the `dynamic` family parameter.
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.. type-along:: Using a jinja calculation with a parameter
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We have the possibility to use a given variable variable inside a jinja calculation:
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.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_050/firefox/20-manual.yml
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:language: yaml
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:caption: firefox/20-proxy.yml
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..
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manual:
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use_for_https:
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description: Also use this proxy for HTTPS
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default: true
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"{{ identifier }}_proxy":
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description: "{{ identifier }} Proxy"
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dynamic:
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- HTTPS
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- SOCKS
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hidden:
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jinja: |
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{% if my_identifier == 'HTTPS' and manual.use_for_https %}
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HTTPS is same has HTTP
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{% endif %}
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params:
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my_identifier:
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type: identifier
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description: |
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in HTTPS case if "manual.use_for_https" is set to True
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address:
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description: "{{ identifier }} address"
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default:
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variable: manual.http_proxy.address
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port:
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description: "{{ identifier }} port"
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default:
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variable: manual.http_proxy.port
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version:
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description: SOCKS host version used by proxy
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choices:
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- v4
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- v5
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default: v5
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disabled:
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type: identifier
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when: 'HTTPS'
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This can be done by defining a `my_identifier` variable.
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This jinja variable comes from the `params` parameter of the `hidden` property.
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.. code-block:: yaml
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params:
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my_identifier:
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type: identifier
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Here the `hidden` property's value is defined by a jinja calculation.
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In this jinja calculation we have a `my_identifier` jinja variable.
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.. code-block:: yaml
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hidden:
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jinja: |
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{% if my_identifier == 'HTTPS' and manual.use_for_https %}
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HTTPS is same has HTTP
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{% endif %}
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params:
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my_identifier:
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type: identifier
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description: |
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in HTTPS case if "manual.use_for_https" is set to True
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.. type-along:: The `when` and `when_not` parameter notation
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.. todo:: ça devrait être sur une autre page. déplacer cela ailleurs
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Handling the SOCKS version
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----------------------------
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Now we need to handle the SOCKS version as show in the firefox configuration screenshot:
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.. image:: images/firefox_soks_version.png
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We'll just add a choice variable with a default value and a disabled property:
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.. code-block:: yaml
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version:
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description: SOCKS host version used by proxy
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choices:
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- v4
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- v5
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default: v5
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disabled:
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type: identifier
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when: 'HTTPS'
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There is still something new about this YAML, though. It is the `when` parameter
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of the `disabled` property. You have two possible notations: `when` or `when_not`.
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These two notations are just a short hand of what we could express in jinja as
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this code:
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.. code-block:: jinja
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{% if identifier == 'HTTPS' %}
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when the identifer equals 'HTTPS' then the SOCKS version is disabled
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{% endif %}
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And the `when_not` parameter is just the logical opposite.
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Here is the final version of our YAML dynamic family:
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.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_050/firefox/20-manual.yml
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:language: yaml
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:caption: firefox/20-proxy.yml
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.. keypoints:: Key points
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**keywords**
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- calculation with a jinja type calculation
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- calculation with a `when` or `when_not` parameter
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- defining a jinja internal variable in a jinja calculation
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**progress**
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Here we have come to the possibility of making any kind of calculations based on the state of the :term:`configuration`.
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This is an important feature to manage the stateful aspect of a configuration.
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