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ENT-13847: Clarified section about variable injection #3647

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olehermanse merged 1 commit into from
May 19, 2026
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ENT-13847: Clarified section about variable injection #3647

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12 changes: 8 additions & 4 deletions content/reference/promise-types/vars.markdown
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Expand Up @@ -382,11 +382,15 @@ two_example_com::

(Promises within the same bundle are evaluated top to bottom, so vars promises further down in a bundle can overwrite previous values of a variable. See [policy evaluation][Policy evaluation] for more information).

## Defining variables in foreign bundles
## Variable injection - Defining variables in foreign bundles

As a general rule, variables can only be defined or re-defined from within the
bundle where they were defined. There are a few notable exceptions to this
general rule which are described below.
As a general rule, variables cannot be defined or re-defined (overwritten) from outside their bundle.
There are 4 exceptions to this rule:

1. `meta` promises define variables in a different meta-suffixed bundle (this bundle is special / "virtual" and does not exist in the policy file).
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@nickanderson nickanderson May 19, 2026

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I dunno that you want to increase the complexity here, I don't know that it adds much but IIRC these _meta suffixed bundles are not precluded from being defined in policy

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@nickanderson nickanderson May 19, 2026

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#+begin_src cfengine3
  bundle agent main
  {
          methods:
         "one";
         "two";
   }
  bundle agent one
  {
        reports: "$(one_meta.tags)";
  }
  bundle agent one_meta
  {
        vars:
          "tags" slist => { "crazy", "stuff" };
  }
  bundle agent two
  {
        meta:
        "tags" slist => { "know", "what", "i'm", "sayin" };

        reports: "$(two_meta.tags)";
  }

#+end_src

#+RESULTS:
: R: crazy
: R: stuff
: R: know
: R: what
: R: i'm
: R: sayin

2. Defining variables into undefined ("virtual") bundles.
3. `commands` modules which communicate using the module protocol can define variables in any bundle.
4. Augments (`def.json`) / Host specific data (`host_specific.json`) can define variables in any bundle.

### Meta type promises

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