json-parse

json-parse is a utility step that parses a JSON string and extracts values using expr-lang expressions.

Configuration

Name	Type	Required	Description
path	string	Y	Path to a JSON file. This path is relative to the temporary workspace that Kargo provisions for use by the promotion process.
outputs	[]object	Y	A list of rules for extracting values from the parsed JSON.
outputs[].name	string	Y	The name of the output variable.
outputs[].fromExpression	string	Y	An expr-lang expression that can extract the value from the JSON file. Note that this expression should not be offset by ${{ and }}. See examples for more details.

Expressions

The fromExpression field supports expr-lang expressions.

note

Expressions should not be offset by ${{ and }} to prevent pre-processing evaluation by Kargo. The json-parse step itself will evaluate these expressions.

An outputs object (a map[string]any) is available to these expressions. It is structured as follows:

Field	Type	Description
outputs	map[string]any	The parsed JSON object.

Outputs

The json-parse step produces the outputs described by the outputs field in its configuration.

Examples

Common Usage

In this example, a values file is parsed to find the container image tag. After cloning the repository and clearing the output directory, the json-parse step parses values.json to extract the image tag from the Freight being promoted. Using dot notation (image.tag), it extracts the nested value from the JSON file.

vars:
- name: gitRepo
  value: https://github.com/example/repo.git
steps:
- uses: git-clone
  config:
    repoURL: ${{ vars.gitRepo }}
    checkout:
    - commit: ${{ commitFrom(vars.gitRepo).ID }}
      path: ./src
    - branch: stage/${{ ctx.stage }}
      create: true
      path: ./out
- uses: git-clear
  config:
    path: ./out
- uses: json-parse
  as: values
  config:
    path: './src/charts/my-chart/values.json'
    outputs:
    - name: imageTag
      fromExpression: image.tag
# Render manifests to ./out, commit, push, etc...

Given the sample input JSON:

{
  "image": {
    "tag": "latest"
  },
  "rbac": {
    "installClusterRoles": true
  }
}

The step would produce the following outputs:

Name	Type	Value
imageTag	string	latest