Ansible – playing with Jinja2 and its whitespace control

4 October 2018 3 By Eric Deleforterie

Jinja2 templating with Ansible is powerfull and sometimes you could have some headache for positionning the result just where you want to respect a configuration file syntax.

Following, I will show you how to manage the whitespace control with Jinja2

Without specifying whitespace control

{
"Clusters":{
"properties": {
{% if Var is defined %}
"myParameter": "value1",
{% else %}
"myParameter": "value2",
{% endif %}
}
}
}

{
  "Clusters":{
    "properties": {
      {% if Var is defined %}
      "myParameter": "value1",
      {% else %}
      "myParameter": "value2",
      {% endif %}
    }
  }
}

{
  "Clusters":{
    "properties": {
      {% if Var is defined %}
      "myParameter": "value1",
      {% else %}
      "myParameter": "value2",
      {% endif %}
    }
  }
}

Result :

{
"Clusters":{
"properties": {
"myParameter": "value2",
}
}
}

{
  "Clusters":{
    "properties": {
            "myParameter": "value2",
          }
  }
}

{
  "Clusters":{
    "properties": {
            "myParameter": "value2",
          }
  }
}

As you can see the spaces of each lines will be keeped causing a gap

With – everywhere

{
"Clusters":{
"properties": {
{%- if Var is defined -%}
"myParameter": "value1",
{%- else -%}
"myParameter": "value2",
{%- endif -%}
}
}
}

{
  "Clusters":{
    "properties": {
      {%- if Var is defined -%}
      "myParameter": "value1",
      {%- else -%}
      "myParameter": "value2",
      {%- endif -%}
    }
  }
}

{
  "Clusters":{
    "properties": {
      {%- if Var is defined -%}
      "myParameter": "value1",
      {%- else -%}
      "myParameter": "value2",
      {%- endif -%}
    }
  }
}

Result :

{
"Clusters":{
"properties": {"myParameter": "value2",}
}
}

{
  "Clusters":{
    "properties": {"myParameter": "value2",}
  }
}

{
  "Clusters":{
    "properties": {"myParameter": "value2",}
  }
}

As you can see it will removed all the spaces and newlines

With a – in front

{
"Clusters":{
"properties": {
{%- if Var is defined %}
"myParameter": "value1",
{% else %}
"myParameter": "value2",
{% endif %}
}
}
}

{
  "Clusters":{
    "properties": {
      {%- if Var is defined %}
      "myParameter": "value1",
      {% else %}
      "myParameter": "value2",
      {% endif %}
    }
  }
}

{
  "Clusters":{
    "properties": {
      {%- if Var is defined %}
      "myParameter": "value1",
      {% else %}
      "myParameter": "value2",
      {% endif %}
    }
  }
}

Result :

{
"Clusters":{
"properties": { "myParameter": "value2",
}
}
}

{
  "Clusters":{
    "properties": {      "myParameter": "value2",
          }
  }
}

{
  "Clusters":{
    "properties": {      "myParameter": "value2",
          }
  }
}

As you can see, the newline before the

{%-

{%- will be removed and the spaces in front of the line are concatenate at the end of the previous line

With a – at the end of each block

{
"Clusters":{
"properties": {
{% if Var is defined -%}
"myParameter": "value1",
{% else -%}
"myParameter": "value2",
{% endif -%}
}
}
}

{
  "Clusters":{
    "properties": {
      {% if Var is defined -%}
      "myParameter": "value1",
      {% else -%}
      "myParameter": "value2",
      {% endif -%}
    }
  }
}

{
  "Clusters":{
    "properties": {
      {% if Var is defined -%}
      "myParameter": "value1",
      {% else -%}
      "myParameter": "value2",
      {% endif -%}
    }
  }
}

Result :

{
"Clusters":{
"properties": {
"myParameter": "value2",
}
}
}

{
  "Clusters":{
    "properties": {
      "myParameter": "value2",
      }
  }
}

{
  "Clusters":{
    "properties": {
      "myParameter": "value2",
      }
  }
}

As you can see this will removed all the spaces and newlines from the removed lines

With a – at the beginning of each block

{
"Clusters":{
"properties": {
{%- if Var is defined %}
"myParameter": "value1",
{%- else %}
"myParameter": "value2",
{%- endif %}
}
}
}

{
  "Clusters":{
    "properties": {
      {%- if Var is defined %}
      "myParameter": "value1",
      {%- else %}
      "myParameter": "value2",
      {%- endif %}
    }
  }
}

{
  "Clusters":{
    "properties": {
      {%- if Var is defined %}
      "myParameter": "value1",
      {%- else %}
      "myParameter": "value2",
      {%- endif %}
    }
  }
}

Result :

{
"Clusters":{
"properties": { "myParameter": "value2", }
}
}

{
  "Clusters":{
    "properties": {      "myParameter": "value2",    }
  }
}

{
  "Clusters":{
    "properties": {      "myParameter": "value2",    }
  }
}

As you can see the all the newlines will be removed and the spaces keeped

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3 Comments

julien says:

24 October 2022 at 15 h 46 min

merci! ça m’a servi

Reply
- Eric Deleforterie says:
  
  24 October 2022 at 16 h 21 min
  
  Ah ah ah, moi aussi pas plus tard qu’il y a 2 semaines avec une topology Knox récalcitrante
  
  Reply
brian lamb says:

2 November 2022 at 19 h 46 min

saved my butt. this was killing me!

Reply

Ansible – playing with Jinja2 and its whitespace control

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