Meetup: initial Setup of Psalm for WC Pay Client (Automattic#2337)

* Initial commit of Psalm introduction to the client
* Setting up Psalm
* update to Psalm config
* Fixing spacing in composer.json
* Fixing spacing in package.json
* Fixing spacing in package.json
* Newline at the end of psalm-loader.php
* Fixing spacing in `psalm.xml`
* Adding newline to psalm bash file.
* Psalm:  add missing immutable annotations
* Psalm: keep fixing violations
* Psalm: level 7
* Psalm: keep fixing violations
* Psalm: keep fixing violations
* Psalm: added to CI
* Psalm: keep fixing violations
* Psalm: fixed failing CI
* Psalm: fixed rebase

Co-authored-by: Vladimir Reznichenko <[email protected]>

Author: dmallory42

.github/workflows/php-lint-test.yml

@@ -26,7 +26,7 @@ jobs:
           tools:       composer
           coverage:    none
       # install dependencies and run linter
-      - run: composer self-update 2.0.6 && composer install --no-progress && ./vendor/bin/phpcs --standard=phpcs.xml.dist $(git ls-files | grep .php$)
+      - run: composer self-update 2.0.6 && composer install --no-progress && ./vendor/bin/phpcs --standard=phpcs.xml.dist $(git ls-files | grep .php$) && ./vendor/bin/psalm
 
   test:
     name:    PHP testing

bin/run-psalm.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+
+set -e
+
+./vendor/bin/psalm $*

composer.json

@@ -23,7 +23,10 @@
       "phpunit/phpunit": "7.5.20",
       "woocommerce/woocommerce-sniffs": "0.1.0",
       "woocommerce/action-scheduler": "3.1.6",
-      "kalessil/production-dependencies-guard": "dev-master"
+      "kalessil/production-dependencies-guard": "dev-master",
+      "vimeo/psalm": "^4.8",
+	    "php-stubs/wordpress-stubs": "^5.7",
+	    "php-stubs/woocommerce-stubs": "^5.4"
     },
     "scripts": {
       "test": [