feat: add port "auto" and remove port: null (#3297)

Author: anshumanv

lib/options.json

@@ -174,7 +174,7 @@
               "type": "string"
             },
             {
-              "type": "null"
+              "enum": ["auto"]
             }
           ],
           "description": "Tells clients connected to devServer to use the provided port."
@@ -424,7 +424,7 @@
           "type": "string"
         },
         {
-          "type": "null"
+          "enum": ["auto"]
         }
       ],
       "description": "Specify a port number to listen for requests on. https://webpack.js.org/configuration/dev-server/#devserverport"

lib/utils/findPort.js

@@ -18,7 +18,7 @@ function runPortFinder() {
 }
 
 function findPort(port) {
-  if (port) {
+  if (port && port !== 'auto') {
     return Promise.resolve(port);
   }
 

test/__snapshots__/validate-options.test.js.snap.webpack4

@@ -82,12 +82,12 @@ exports[`options validate should throw an error on the "client" option with '{"p
 exports[`options validate should throw an error on the "client" option with '{"port":true}' value 1`] = `
 "ValidationError: Invalid configuration object. Object has been initialized using a configuration object that does not match the API schema.
  - configuration.client.port should be one of these:
-   number | string | null
+   number | string | \\"auto\\"
    -> Tells clients connected to devServer to use the provided port.
    Details:
     * configuration.client.port should be a number.
     * configuration.client.port should be a string.
-    * configuration.client.port should be a null."
+    * configuration.client.port should be \\"auto\\"."
 `;
 
 exports[`options validate should throw an error on the "client" option with '{"progress":""}' value 1`] = `
@@ -361,12 +361,23 @@ exports[`options validate should throw an error on the "open" option with '{"tar
 exports[`options validate should throw an error on the "port" option with 'false' value 1`] = `
 "ValidationError: Invalid configuration object. Object has been initialized using a configuration object that does not match the API schema.
  - configuration.port should be one of these:
-   number | string | null
+   number | string | \\"auto\\"
    -> Specify a port number to listen for requests on. https://webpack.js.org/configuration/dev-server/#devserverport
    Details:
     * configuration.port should be a number.
     * configuration.port should be a string.
-    * configuration.port should be a null."
+    * configuration.port should be \\"auto\\"."
+`;
+
+exports[`options validate should throw an error on the "port" option with 'null' value 1`] = `
+"ValidationError: Invalid configuration object. Object has been initialized using a configuration object that does not match the API schema.
+ - configuration.port should be one of these:
+   number | string | \\"auto\\"
+   -> Specify a port number to listen for requests on. https://webpack.js.org/configuration/dev-server/#devserverport
+   Details:
+    * configuration.port should be a number.
+    * configuration.port should be a string.
+    * configuration.port should be \\"auto\\"."
 `;
 
 exports[`options validate should throw an error on the "proxy" option with '[]' value 1`] = `

test/__snapshots__/validate-options.test.js.snap.webpack5

@@ -82,12 +82,12 @@ exports[`options validate should throw an error on the "client" option with '{"p
 exports[`options validate should throw an error on the "client" option with '{"port":true}' value 1`] = `
 "ValidationError: Invalid configuration object. Object has been initialized using a configuration object that does not match the API schema.
  - configuration.client.port should be one of these:
-   number | string | null
+   number | string | \\"auto\\"
    -> Tells clients connected to devServer to use the provided port.
    Details:
     * configuration.client.port should be a number.
     * configuration.client.port should be a string.
-    * configuration.client.port should be a null."
+    * configuration.client.port should be \\"auto\\"."
 `;
 
 exports[`options validate should throw an error on the "client" option with '{"progress":""}' value 1`] = `
@@ -361,12 +361,23 @@ exports[`options validate should throw an error on the "open" option with '{"tar
 exports[`options validate should throw an error on the "port" option with 'false' value 1`] = `
 "ValidationError: Invalid configuration object. Object has been initialized using a configuration object that does not match the API schema.
  - configuration.port should be one of these:
-   number | string | null
+   number | string | \\"auto\\"
    -> Specify a port number to listen for requests on. https://webpack.js.org/configuration/dev-server/#devserverport
    Details:
     * configuration.port should be a number.
     * configuration.port should be a string.
-    * configuration.port should be a null."
+    * configuration.port should be \\"auto\\"."
+`;
+
+exports[`options validate should throw an error on the "port" option with 'null' value 1`] = `
+"ValidationError: Invalid configuration object. Object has been initialized using a configuration object that does not match the API schema.
+ - configuration.port should be one of these:
+   number | string | \\"auto\\"
+   -> Specify a port number to listen for requests on. https://webpack.js.org/configuration/dev-server/#devserverport
+   Details:
+    * configuration.port should be a number.
+    * configuration.port should be a string.
+    * configuration.port should be \\"auto\\"."
 `;
 
 exports[`options validate should throw an error on the "proxy" option with '[]' value 1`] = `

test/server/port-option.test.js

@@ -78,7 +78,7 @@ describe('port', () => {
     afterAll(testServer.close);
   });
 
-  describe('is null', () => {
+  describe('is auto', () => {
     beforeAll((done) => {
       server = testServer.start(
         config,
@@ -87,7 +87,7 @@ describe('port', () => {
             directory: staticDirectory,
             watch: false,
           },
-          port: null,
+          port: 'auto',
         },
         done
       );

test/validate-options.test.js

@@ -70,7 +70,7 @@ const tests = {
       {
         host: '',
         path: '',
-        port: null,
+        port: 'auto',
       },
       {
         progress: false,
@@ -247,8 +247,8 @@ const tests = {
     failure: ['', [], { foo: 'bar' }, { target: 90 }, { app: true }],
   },
   port: {
-    success: ['', 0, null],
-    failure: [false],
+    success: ['', 0, 'auto'],
+    failure: [false, null],
   },
   proxy: {
     success: [