🥇How does GitLab-CI inherit environment variables?

Variables in Gitlab can be defined in several places:

In group settings
In project settings
Inside .gitlab-ci.yml

In group and project settings, variables can be defined as either 'file' or 'regular variable' with the options 'protected' and 'masked' checked.

Let's start with simple inheritance and gradually complicate it.

A final list of priority levels can be found at the end of the document.

Inheritance with groups [sources]

Variables from groups are inherited, with the rule that the closer the group is to the project, the more important its value is.

Groups with variables

.gitlab-ci.yml

image: busybox:latest
variables:
  GIT_STRATEGY: none

echo:
  stage: test
  script:
    - echo $MSG

Pipeline result

$ echo $MSG
B

If the variable was not specified in group B, we would see value A.

Inheritance of variables inside .gitlab-ci.yml [sources]

Here, it's quite simple: you can define a global variable or override it within the job.

Groups with variables

.gitlab-ci.yml

Now let's create 2 jobs, in one of which we explicitly specify $MSG.

image: busybox:latest
variables:
  GIT_STRATEGY: none
  MSG: "Custom in global .gitlab-ci.yml"

echo:
  stage: test
  script:
    - echo $MSG

echo with var:
  stage: test
  variables:
    MSG: "Custom in job .gitlab-ci.yml"
  script:
    - echo $MSG

Pipeline result

echo:

$ echo $MSG
Custom in global .gitlab-ci.yml
Job succeeded

echo with vars:

$ echo $MSG
Custom in job .gitlab-ci.yml
Job succeeded

Inheritance with groups and inside .gitlab-ci.yml [sources]

Let's try to combine the previous 2 examples. Group variables take precedence over variables inside .gitlab-ci.yml.

Groups with variables

.gitlab-ci.yml

image: busybox:latest
variables:
  GIT_STRATEGY: none
  MSG: "Custom in global .gitlab-ci.yml"

echo:
  stage: test
  script:
    - echo $MSG

echo with var:
  stage: test
  variables:
    MSG: "Custom in job .gitlab-ci.yml"
  script:
    - echo $MSG

Pipeline result

echo:
```
$ echo $MSG
Y
Job succeeded
```
echo with vars:
```
$ echo $MSG
Y
Job succeeded
```

Inheritance with variable specification in project settings [sources]

Variables in project settings ALWAYS have the highest priority! Variables specified inside .gitlab-ci.yml play no role.

Groups with variables

Group variables have lower priority.

.gitlab-ci.yml

We'll use the file from the previous example. Here again, there are variables specified inside .gitlab-ci.yml, but group variables still take precedence over them.

image: busybox:latest
variables:
  GIT_STRATEGY: none
  MSG: "Custom in global .gitlab-ci.yml"

echo:
  stage: test
  script:
    - echo $MSG

echo with var:
  stage: test
  variables:
    MSG: "Custom in job .gitlab-ci.yml"
  script:
    - echo $MSG

Pipeline result

echo:
```
$ echo $MSG
project-3
Job succeeded
```
echo with vars:
```
$ echo $MSG
project-3
Job succeeded
```

Inheritance with empty value [sources]

An empty value is still a value
An empty value is not Null

Groups with variables

.gitlab-ci.yml

image: busybox:latest
variables:
  GIT_STRATEGY: none
  MSG: "Custom in global .gitlab-ci.yml"

echo:
  stage: test
  script:
    - echo $MSG

echo with var:
  stage: test
  variables:
    MSG: "Custom in job .gitlab-ci.yml"
  script:
    - echo $MSG

Pipeline result

echo:
```
$ echo $MSG
Job succeeded
```
echo with vars:
```
$ echo $MSG
Job succeeded
```

Inheritance with include and groups [sources]

Here we will try to include project-3 in project-2
Groups take precedence in this case.

Groups with variables

.gitlab-ci.yml

And we will define the variable globally in .gitlab-ci.yml

variables:
 MSG: "With include .gitlab-ci.yml"
include:
 - project: how-is-gitlab-ci-inherit-environment-variables/z/y/project-3
   file: '.gitlab-ci.yml'

Pipeline result

echo:
```
$ echo $MSG
B
Job succeeded
```
echo with vars:
```
$ echo $MSG
B
Job succeeded
```

Inheritance with include [sources]

Here we will try to include project-3 in project-2.
With the condition that neither the groups nor the project itself have any variables.

Groups with variables

.gitlab-ci.yml

The same as in the previous example

variables:
 MSG: "With include .gitlab-ci.yml"
include:
 - project: how-is-gitlab-ci-inherit-environment-variables/z/y/project-3
   file: '.gitlab-ci.yml'

Pipeline result

echo:

$ echo $MSG
With include .gitlab-ci.yml
Job succeeded

echo with vars:

$ echo $MSG
Custom in job .gitlab-ci.yml
Job succeeded

The following results in priorities:

Variables in project settings
Variables in groups
Variables strictly specified within jobs (including included files)
Global variables inside .gitlab-ci.yml
Global variables inside included files

Conclusion

The least obvious point is that the rule "the closer the variable is to the code, the more important it is" applies first to groups, and then the same rule applies to variables within .gitlab-ci.yml, but only on the condition that variables in groups are not specified.
Furthermore, an important point is understanding that the global space for the main and included .gitlab-ci.yml is shared. And the file into which the include occurs has priority.

Source: habr.com