New Example: Preserve Query Strings on redirect

preserve-query-strings-on-redirect/README.md

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+## Preserve Query Strings on Redirect
+
+**CloudFront Functions event type: viewer request**
+
+This function provides an example of how to preserve query strings when performing a redirect.
+
+**Testing the function**
+
+To validate that the function is working as expected, you can use the JSON test objects in the `test-objects` directory. To test, use the `test-function` CLI command as shown in the following examples:
+
+**Preserve Query Strings**
+
+This test validates that requests with query strings will be redirected to the `www.example.com` domain preserving the requested URL and query strings.
+
+```shell
+# Get the current ETag value
+$ aws cloudfront describe-function --name preserve-query-strings-on-redirect
+# Run the test
+$ aws cloudfront test-function --if-match EXXXXXXXXXXXX --name preserve-query-strings-on-redirect --event-object fileb://preserve-query-strings-on-redirect/test-objects/query-strings.json
+```
+
+If the function has been set up correctly, you should see a result similar to the following with the redirect being issued (`location` header being returned) in the `FunctionOutput` JSON object. Notice that the requested URL and query strings are included in the `value`:
+
+```json
+{
+    "TestResult": {
+        "FunctionSummary": {
+            "Name": "preserve-query-strings-on-redirect",
+            "Status": "UNPUBLISHED",
+            "FunctionConfig": {
+                "Comment": "",
+                "Runtime": "cloudfront-js-2.0"
+            },
+            "FunctionMetadata": {
+                "FunctionARN": "arn:aws:cloudfront::060232822672:function/preserve-query-strings-on-redirect",
+                "Stage": "DEVELOPMENT",
+                "CreatedTime": "2024-10-02T14:08:21.623000+00:00",
+                "LastModifiedTime": "2024-10-02T14:08:44.844000+00:00"
+            }
+        },
+        "ComputeUtilization": "10",
+        "FunctionExecutionLogs": [],
+        "FunctionErrorMessage": "",
+        "FunctionOutput": "{\"response\":{\"headers\":{\"location\":{\"value\":\"https://www.example.com/example-page?name=example-name&test=example-test-query-string&querymv=val1&querymv=val2,val3\"}},\"statusDescription\":\"Moved Permanently\",\"cookies\":{},\"statusCode\":301}}"
+    }
+}
+```
+
+**Redirect still works when no query strings in request**
+
+```shell
+# Get the current ETag value
+$ aws cloudfront describe-function --name preserve-query-strings-on-redirect
+# Run the test
+$ aws cloudfront test-function --if-match EXXXXXXXXXXXX --name preserve-query-strings-on-redirect --event-object fileb://preserve-query-strings-on-redirect/test-objects/no-query-strings.json
+```
+
+If the function has been set up correctly, you should see a result similar to the following with the redirect being issued (`location` header being returned) in the `FunctionOutput` JSON object. Notice that the requested URL is included in the `value`:
+
+```json
+{
+    "TestResult": {
+        "FunctionSummary": {
+            "Name": "preserve-query-strings-on-redirect",
+            "Status": "UNPUBLISHED",
+            "FunctionConfig": {
+                "Comment": "",
+                "Runtime": "cloudfront-js-2.0"
+            },
+            "FunctionMetadata": {
+                "FunctionARN": "arn:aws:cloudfront::060232822672:function/preserve-query-strings-on-redirect",
+                "Stage": "DEVELOPMENT",
+                "CreatedTime": "2024-10-02T14:08:21.623000+00:00",
+                "LastModifiedTime": "2024-10-02T14:08:44.844000+00:00"
+            }
+        },
+        "ComputeUtilization": "7",
+        "FunctionExecutionLogs": [],
+        "FunctionErrorMessage": "",
+        "FunctionOutput": "{\"response\":{\"headers\":{\"location\":{\"value\":\"https://www.example.com/example-page\"}},\"statusDescription\":\"Moved Permanently\",\"cookies\":{},\"statusCode\":301}}"
+    }
+}
+```

preserve-query-strings-on-redirect/index.js

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+function handler(event) {
+    const request = event.request;
+    const uri = request.uri;
+    const customRedirectLogic = true;
+    var queryStringAsString = '';
+
+    const qs = []
+    for (const key in request.querystring) {
+      if (request.querystring[key].multiValue) {
+        request.querystring[key].multiValue.forEach((mv) => { qs.push(key + '=' + mv.value) })
+      } else {
+        qs.push(key + '=' + request.querystring[key].value)
+      }
+    }
+
+    if (qs.length !== 0) {
+      queryStringAsString = '?' + qs.join('&')
+    }
+
+    if (customRedirectLogic) {
+        const response = {
+            statusCode: 301,
+            statusDescription: 'Moved Permanently',
+            headers:
+            {
+                location: { value: `https://www.example.com${uri}${queryStringAsString}` },
+            }
+        }
+
+        return response;
+    }
+
+    return request;
+}

preserve-query-strings-on-redirect/test-objects/no-query-strings.json

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+{
+    "version": "1.0",
+    "context": {
+        "eventType": "viewer-request"
+    },
+    "viewer": {
+        "ip": "0.0.0.0"
+    },
+    "request": {
+        "method": "GET",
+        "uri": "/example-page",
+        "headers": {
+            "host": { "value": "www.example.com" },
+            "accept": { "value": "text/html", "multivalue": [ { "value": "text/html" }, { "value": "application/xhtml+xml" } ] }
+        }
+    }
+}

preserve-query-strings-on-redirect/test-objects/query-strings.json

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+{
+    "version": "1.0",
+    "context": {
+        "eventType": "viewer-request"
+    },
+    "viewer": {
+        "ip": "0.0.0.0"
+    },
+    "request": {
+        "method": "GET",
+        "uri": "/example-page",
+        "querystring": {
+            "name": { "value": "example-name"},
+            "test": {"value": "example-test-query-string"},
+            "querymv": {
+                "value": "val1",
+                "multiValue": [
+                    {"value": "val1"},
+                    {"value": "val2,val3"}
+                ]}
+        },
+        "headers": {
+            "host": { "value": "www.example.com" },
+            "accept": { "value": "text/html", "multivalue": [ { "value": "text/html" }, { "value": "application/xhtml+xml" } ] }
+        }
+    }
+}