Example 1: Using an Expression to Specify the Execution Condition

You can reference contexts with expressions to specify the execution condition of a job. An expression can be any combination of contexts, operators, functions, or literals. Contexts can be accessed programmatically with expressions, so information such as pipeline runs, sources, variables, and jobs can be transferred within a pipeline.

Figure 1 Expressions

Example:

The following expression shows that a job runs only when the running branch of the specified code source is master.

${{ sources.my_repo.target_branch == 'master' }}

• Pipeline contexts
• Operator
  The following table lists the operators that can be used in expressions.

  Table 1 Operators

  Operator	Description
  .	Attribute reference. For example, the ${{ pipeline.trigger_type }} expression can be used to obtain the trigger type.
  !	False. For example, the ${{ !startsWith(sources.my_repo.target_branch, 'release') }} can be used to check whether the branch of the pipeline's code source does not start with "release".
  ==	Equal. For example, the ${{ pipeline.trigger_type == 'Manual' }} expression can be used to check whether a pipeline is triggered manually.
  !=	Not equal. For example, the ${{ pipeline.trigger_type != 'Manual' }} expression can be used to check whether a pipeline is not triggered manually.
  &&	And. For example, the ${{ pipeline.trigger_type == 'Manual' && sources.my_repo.target_branch == 'master' }} expression can be used to check whether a pipeline is triggered manually and the branch of the pipeline code source is master.
  ||	Or. For example, the ${{ pipeline.trigger_type == 'Manual' || sources.my_repo.target_branch == 'master' }} expression can be used to check whether a pipeline is triggered manually or the branch of the pipeline code source is master.

• Function

  The following table lists the functions that can be used in expressions.

  Table 2 Built-in functions

  Function	Description
  contains	Format contains(search, item) Description If search contains item, this function returns true. If search is an array and item is an element in the array, this function returns true. If search is a string and item is a substring of search, the function returns true. Example contains('abc', 'bc') returns true.
  startsWith	Format startsWith(searchString, searchValue) Description If searchString starts with searchValue, this function returns true. Example startsWith('abc', 'ab') returns true.
  endsWith	Format endsWith(searchString, searchValue) Description If searchString ends with searchValue, this function returns true. Example endsWith('abc', 'bc') returns true.
  Object filter	You can use the * syntax to apply a filter and select matching items in a collection. The following is the context of a job execution. { "check_job": { "status": "COMPLETED", "metrics": { "critical": "0", "major": "0" } }, "demo_job": { "status": "FAILED" } } jobs.*.status indicates the status of all jobs. Therefore, ['COMPLETED', 'FAILED'] is returned. Filters can be used together with the contains function. For example, contains(jobs.*.status, 'FAILED') will return true because jobs.*.status contains FAILED.