Merge pull request #6 from gruntwork-io/feature/pre-exec-code

Add support for custom code execution

README.md

@@ -1,4 +1,5 @@
 # terragrunt-action
+
 A GitHub Action for installing and running Terragrunt
 
 ## Inputs
@@ -13,25 +14,30 @@ Supported GitHub action inputs:
 | tg_command | Terragrunt command to execute                     |  `true`  |
 | tg_comment | Add comment to Pull request with execution output | `false`  |
 
+## Environment Variables
+
+Supported environment variables:
+
+| Input Name            | Description                                                                                                 | 
+|:----------------------|:------------------------------------------------------------------------------------------------------------|
+| GITHUB_TOKEN          | GitHub token used to add comment to Pull request                                                            |
+| TF_LOG                | Log level for Terraform                                                                                     |
+| TF_VAR_name           | Define custom variable name as inputs                                                                       |
+| INPUT_PRE_EXEC_number | Environment variable is utilized to provide custom commands that will be executed before running Terragrunt |
+
 ## Outputs
 
 Outputs of GitHub action:
 
 | Input Name          | Description                     |
 |:--------------------|:--------------------------------|
 | tg_action_exit_code | Terragrunt exit code            |
-| tg_action_output    | Terragrunt output as plain text | 
-
-## Environment Variables
-
-Supported environment variables:
-* `GITHUB_TOKEN` - GitHub token used to add comment to Pull request
-* `TF_LOG` - log level for Terraform
-* `TF_VAR_name` - Define custom variable name as inputs
+| tg_action_output    | Terragrunt output as plain text |
 
 ## Usage
 
 Example definition of Github Action workflow:
+
 ```yaml
 name: 'Terragrunt GitHub Actions'
 on:
@@ -59,7 +65,7 @@ jobs:
 
   plan:
     runs-on: ubuntu-latest
-    needs: [checks]
+    needs: [ checks ]
     steps:
       - name: 'Checkout'
         uses: actions/checkout@master
@@ -74,7 +80,7 @@ jobs:
 
   deploy:
     runs-on: ubuntu-latest
-    needs: [plan]
+    needs: [ plan ]
     environment: 'prod'
     if: github.ref == 'refs/heads/master'
     steps:
@@ -90,3 +96,20 @@ jobs:
           tg_command: 'apply'
 ```
 
+Example of passing custom code before running Terragrunt:
+
+```yaml
+...
+- name: Plan
+  uses: gruntwork-io/terragrunt-action@v1
+  env:
+    # configure git to use custom token to clone repository.
+    INPUT_PRE_EXEC_1: |
+      git config --global url."https://user:${{secrets.PAT_TOKEN}}@github.com".insteadOf "https://github.com"
+    # print git configuration
+    INPUT_PRE_EXEC_2: |
+      git config --global --list
+  with:
+    tg_command: 'plan'
+...
+```

src/main.sh

@@ -80,6 +80,22 @@ function setup_git {
   git config --global --add safe.directory /github/workspace
 }
 
+# Run INPUT_PRE_EXEC_* environment variables as Bash code
+function setup_pre_exec {
+  env
+  # Get all environment variables that match the pattern INPUT_PRE_EXEC_*
+  local -r pre_exec_vars=$(env | grep -o '^INPUT_PRE_EXEC_[0-9]\+' | sort)
+  # Loop through each pre-execution variable and execute its value (Bash code)
+  local pre_exec_command
+  while IFS= read -r pre_exec_var; do
+    log "Evaluating ${pre_exec_var}"
+    pre_exec_command="${!pre_exec_var}"
+    if [ -n "$pre_exec_command" ]; then
+        eval "$pre_exec_command"
+    fi
+  done <<< "$pre_exec_vars"
+}
+
 function main {
   log "Starting Terragrunt Action"
   trap 'log "Finished Terragrunt Action execution"' EXIT
@@ -104,6 +120,8 @@ function main {
     exit 1
   fi
   setup_git
+  setup_pre_exec
+
   install_terraform "${tf_version}"
   install_terragrunt "${tg_version}"