From a133736b0e2324100cca7dd01f302d8d3d2d1c0d Mon Sep 17 00:00:00 2001
From: mrmodise <modisemorebodi@gmail.com>
Date: Sun, 11 Oct 2020 19:08:06 +0200
Subject: [PATCH] fix: allow array query parameter for a single value

Signed-off-by: mrmodise <modisemorebodi@gmail.com>
---
 .../coercion/coercion.acceptance.ts           | 32 +++++++++++++++++++
 .../rest/src/coercion/coerce-parameter.ts     | 21 ++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/packages/rest/src/__tests__/acceptance/coercion/coercion.acceptance.ts b/packages/rest/src/__tests__/acceptance/coercion/coercion.acceptance.ts
index 0278cc8eab1b..4fc6e8b43a84 100644
--- a/packages/rest/src/__tests__/acceptance/coercion/coercion.acceptance.ts
+++ b/packages/rest/src/__tests__/acceptance/coercion/coercion.acceptance.ts
@@ -144,6 +144,14 @@ describe('Coercion', () => {
     ) {
       return filter;
     }
+
+    @get('/array-parameters-from-query')
+    getArrayFromQuery(
+      @param.array('stringArray', 'query', {type: 'string'})
+      stringArray: string[],
+    ) {
+      return stringArray;
+    }
   }
 
   it('coerces parameter in path from string to number', async () => {
@@ -283,6 +291,30 @@ describe('Coercion', () => {
     );
   });
 
+  describe('coerces array parameters', () => {
+    it('coerces a single value into an array with one item', async () => {
+      const response = await client
+        .get('/array-parameters-from-query')
+        .query({
+          stringArray: 'hello',
+        })
+        .expect(200);
+
+      expect(response.body).to.eql(['hello']);
+    });
+
+    it('preserves array values as arrays', async () => {
+      const response = await client
+        .get('/array-parameters-from-query')
+        .query({
+          stringArray: ['hello', 'loopback', 'world'],
+        })
+        .expect(200);
+
+      expect(response.body).to.eql(['hello', 'loopback', 'world']);
+    });
+  });
+
   async function givenAClient() {
     app = new RestApplication({rest: givenHttpServerConfig()});
     app.controller(MyController);
diff --git a/packages/rest/src/coercion/coerce-parameter.ts b/packages/rest/src/coercion/coerce-parameter.ts
index 3f2404af15ae..973022e48704 100644
--- a/packages/rest/src/coercion/coerce-parameter.ts
+++ b/packages/rest/src/coercion/coerce-parameter.ts
@@ -95,6 +95,9 @@ export async function coerceParameter(
     case 'password':
       result = coerceString(data, spec);
       break;
+    case 'array':
+      result = coerceArray(data, spec);
+      break;
   }
 
   if (result != null) {
@@ -103,6 +106,7 @@ export async function coerceParameter(
       await validateParam(spec, data, options);
       return result;
     }
+
     result = await validateParam(spec, result, options);
   }
   return result;
@@ -199,6 +203,23 @@ async function coerceObject(input: string | object, spec: ParameterObject) {
   return data;
 }
 
+function coerceArray(
+  data: string | number | boolean | object,
+  spec: ParameterObject,
+) {
+  if (spec.in === 'query') {
+    if (
+      typeof data === 'string' ||
+      typeof data === 'number' ||
+      typeof data === 'boolean'
+    ) {
+      return [data];
+    }
+  }
+
+  return data;
+}
+
 function validateParam(
   spec: ParameterObject,
   // eslint-disable-next-line @typescript-eslint/no-explicit-any