chore: Interpolate slice of strings in the manifest (#4993)

closes #4928


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internal/pkg/manifest/interpolate.go

@@ -5,6 +5,7 @@ package manifest
 
 import (
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"os"
 	"regexp"
@@ -72,7 +73,21 @@ func (i *Interpolator) applyInterpolation(node *yaml.Node) error {
 		if err != nil {
 			return err
 		}
-		node.Value = interpolated
+		var s []string
+		if err = json.Unmarshal([]byte(interpolated), &s); err == nil && len(s) != 0 {
+			seqNode := &yaml.Node{
+				Kind: yaml.SequenceNode,
+			}
+			for _, value := range s {
+				seqNode.Content = append(seqNode.Content, &yaml.Node{
+					Kind:  yaml.ScalarNode,
+					Value: value,
+				})
+			}
+			*node = *seqNode
+		} else {
+			node.Value = interpolated
+		}
 	default:
 		for _, content := range node.Content {
 			if err := i.applyInterpolation(content); err != nil {

internal/pkg/manifest/interpolate_test.go

@@ -59,6 +59,9 @@ cpu: 256#${CPU}
 memory: 512    # ${Memory}
 variables:
   ${foo}: ${bar}
+network:
+  vpc:
+    security_groups: ${SECURITY_GROUPS}
 `,
 			inputEnvVar: map[string]string{
 				"0accountID":               "1234567890",
@@ -69,6 +72,7 @@ variables:
 				"CPU":                      "512",
 				"bar":                      "bar",
 				"ip":                       "10.24.34.0/23",
+				"SECURITY_GROUPS":          `["sg-1","sg-2","sg-3"]`,
 			},
 
 			wanted: `# The manifest for the ${name} service.
@@ -89,6 +93,12 @@ cpu: 256#512
 memory: 512 # ${Memory}
 variables:
   ${foo}: bar
+network:
+  vpc:
+    security_groups:
+      - sg-1
+      - sg-2
+      - sg-3
 `,
 		},
 	}

site/content/docs/developing/manifest-env-var.en.md

@@ -15,8 +15,27 @@ image:
 ```
 When Copilot defines the container, it will use the image located at `id.dkr.ecr.zone.amazonaws.com/project-name` and with tag `version01`.
 
+It is also possible to interpolate `Array of Strings`, from environment variables in your manifest files:
+
+```yaml
+network:
+  vpc:
+    security_groups: ${SECURITY_GROUPS}
+```
+
+Suppose the shell has `SECURITY_GROUPS=["sg-06b511534b8fa8bbb","sg-06b511534b8fa8bbb","sg-0e921ad50faae7777"]`, the manifest example will be resolved as
+
+```yaml
+network:
+  vpc:
+    security_groups:
+      - sg-06b511534b8fa8bbb
+      - sg-06b511534b8fa8bbb
+      - sg-0e921ad50faae7777
+```
+
 !!! Info
-    At this moment, you can only substitute shell environment variables for fields that accept strings, including `String` (e.g., `image.location`), `Array of Strings` (e.g., `entrypoint`), or `Map` where the value type is `String` (e.g., `secrets`).
+    At this moment, you can only substitute shell environment variables for fields that accept strings, including `String` (e.g., `image.location`), `Array of Strings` (e.g., `entrypoint`), or `Map` where the value type is `String` or `Array of Strings` (e.g., `secrets`).
 
 ## Predefined variables
 Predefined variables are reserved variables that will be resolved by Copilot when interpreting the manifest. Currently, available predefined environment variables include: