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Tips

Using YAML references

It is recommended to use one deploy section per target, e.g. per branch.

For example:

deploy:
  - provider: s3
    bucket: production_bucket
    on:
      branch: production
  - provider: s3
    bucket: staging_bucket
    on:
      branch: staging

However, if you need to set many other attributes, maybe including secure values, then this can become pretty verbose.

In such cases YAML's reference feature can come in handy:

deploy:
  - &s3
    provider: s3
    access_key_id:
      secure: ...
    secret_access_key:
      secure: ...
    region: eu-central-1
    bucket: production_bucket
    on:
      branch: production
  - <<: *s3
    provider: s3
    bucket: staging_bucket
    on:
      branch: staging

This results in:

{
  "deploy": [
    {
      "true": {
        "branch": "production"
      },
      "provider": "s3",
      "bucket": "production_bucket",
      "region": "eu-central-1",
      "access_key_id": {
        "secure": "..."
      },
      "secret_access_key": {
        "secure": "..."
      }
    },
    {
      "true": {
        "branch": "staging"
      },
      "provider": "s3",
      "bucket": "staging_bucket",
      "region": "eu-central-1",
      "access_key_id": {
        "secure": "..."
      },
      "secret_access_key": {
        "secure": "..."
      }
    }
  ]
}

We recommend referencing, and reusing an existing entry, instead of adding extra keys, e.g. on the root section, as this would yield extra warnings and can, potentially, break your config in unexpected ways.

Another example is using references on the matrix.include section:

matrix:
  include:
    - &job
      compiler: gcc
      apt:
        packages:
        - gcc-multilib
    - <<: *job
      compiler: clang

This results in:

{
  "matrix": {
    "include": [
      {
        "apt": {
          "packages": [
            "gcc-multilib"
          ]
        },
        "compiler": "gcc"
      },
      {
        "apt": {
          "packages": [
            "gcc-multilib"
          ]
        },
        "compiler": "clang"
      }
    ]
  }
}

The following is an example of extra keys added to the root section, which will result in validation warnings and errors.

This syntax is not recommended.

_packages:
- &1
  apt:
    packages:
    - gcc-multilib
matrix:
  include:
  - env:
      FOO=foo
    addons: *1
  - env:
      BAR=bar
    addons: *1

Instead, we recommend folding the reference entry into the matrix.include section like so:

matrix:
  include:
  - env:
      - FOO=foo
    addons: &addons
        apt:
          packages:
          - gcc-multilib
  - env:
      - BAR=bar
    addons: *addons

Or:

matrix:
  include:
  - &job
    env:
      - FOO=foo
    addons:
        apt:
          packages:
          - gcc-multilib
  - *job
    env:
      - BAR=bar

Common YAML mistakes

Nesting maps in sequences

Starting a line with a dash - indicates an entry in a sequence. Sometimes that is not intended. For example the following YAML:

deploy:
  - provider: heroku

would result in:

{
  "deploy": [
    {
      "provider": "heroku"
    }
  ]
}

Instead a simple map is required here, so omitting the dash is important:

deploy:
  provider: heroku

This results in:

{
  "deploy": {
    "provider": "heroku"
  }
}

Unquoted command containing a colon

In YAML an unquoted line with a colon will result in a map. For example the following YAML:

after_script:
- echo "========== test log: ============"

results in this:

{ after_script: [ { 'echo "========== test log': '============"' } ] }

Note the command was split into a map.

To solve this either extract the command into a file, or quote the command:

after_script:
- 'echo "========== test log: ============"'

Results in:

{ after_script: [ 'echo "========== test log: ============"' ] }

Our parser will try fixing this mistake, and gets it right in many, but not all cases.

Broken nesting

In YAML nesting is crucial.

The following looks like mistakenly hitting the tab key once broke the nesting:

addons:
  postgresql: '9.4'
  before_script:
  - psql -c 'create database peepchat_test;' -U postgres

This should have been:

addons:
  postgresql: '9.4'
before_script:
  - psql -c 'create database peepchat_test;' -U postgres