Add basic linting of JSON files using eslint-plugin-json

By adding basic linting of JSON files, we can ensure that they're actually valid and prevent e.g. test-failures caused by *accidental* errors when editing the `test/test_manifest.json` file (something that I've done *many* times myself).

For now this simply uses the `recommended` configuration, but we can obviously tweak this later if/when needed. Please find additional information at https://github.com/azeemba/eslint-plugin-json

.eslintrc

@@ -6,6 +6,7 @@
 
   "plugins": [
     "import",
+    "json",
     "mozilla",
     "no-unsanitized",
     "sort-exports",
@@ -13,6 +14,7 @@
   ],
 
   "extends": [
+    "plugin:json/recommended",
     "plugin:prettier/recommended"
   ],
 

gulpfile.js

@@ -1742,7 +1742,7 @@ gulp.task("lint", function (done) {
   const esLintOptions = [
     "node_modules/eslint/bin/eslint",
     "--ext",
-    ".js,.jsm",
+    ".js,.jsm,.json",
     ".",
     "--report-unused-disable-directives",
   ];

package-lock.json

@@ -4905,6 +4905,16 @@
         }
       }
     },
+    "eslint-plugin-json": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/eslint-plugin-json/-/eslint-plugin-json-3.0.0.tgz",
+      "integrity": "sha512-7qoY5pbzBLEttJWy4/cDtULK3EKglgIwfXk5Yqp3StJaQ4Bu4Jmp0n2fJN5vBe/hLGaECupq3edn1j/k7O0bFA==",
+      "dev": true,
+      "requires": {
+        "lodash": "^4.17.21",
+        "vscode-json-languageservice": "^4.0.2"
+      }
+    },
     "eslint-plugin-mozilla": {
       "version": "2.10.0",
       "resolved": "https://registry.npmjs.org/eslint-plugin-mozilla/-/eslint-plugin-mozilla-2.10.0.tgz",
@@ -7885,6 +7895,12 @@
         "minimist": "^1.2.5"
       }
     },
+    "jsonc-parser": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/jsonc-parser/-/jsonc-parser-3.0.0.tgz",
+      "integrity": "sha512-fQzRfAbIBnR0IQvftw9FJveWiHp72Fg20giDrHz6TdfB12UH/uue0D3hm57UB5KgAVuniLMCaS8P1IMj9NR7cA==",
+      "dev": true
+    },
     "jsonify": {
       "version": "0.0.0",
       "resolved": "https://registry.npmjs.org/jsonify/-/jsonify-0.0.0.tgz",
@@ -16580,6 +16596,44 @@
       "integrity": "sha1-wGavtYK7HLQSjWDqkjkulNXp2+w=",
       "dev": true
     },
+    "vscode-json-languageservice": {
+      "version": "4.1.4",
+      "resolved": "https://registry.npmjs.org/vscode-json-languageservice/-/vscode-json-languageservice-4.1.4.tgz",
+      "integrity": "sha512-/UqaE58BVFdePM9l971L6xPRLlCLNk01aovf1Pp9hB/8pytmd2s9ZNEnS1JqYyQEJ1k5/fEBsWOdhQlNo4H7VA==",
+      "dev": true,
+      "requires": {
+        "jsonc-parser": "^3.0.0",
+        "minimatch": "^3.0.4",
+        "vscode-languageserver-textdocument": "^1.0.1",
+        "vscode-languageserver-types": "^3.16.0",
+        "vscode-nls": "^5.0.0",
+        "vscode-uri": "^3.0.2"
+      }
+    },
+    "vscode-languageserver-textdocument": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/vscode-languageserver-textdocument/-/vscode-languageserver-textdocument-1.0.1.tgz",
+      "integrity": "sha512-UIcJDjX7IFkck7cSkNNyzIz5FyvpQfY7sdzVy+wkKN/BLaD4DQ0ppXQrKePomCxTS7RrolK1I0pey0bG9eh8dA==",
+      "dev": true
+    },
+    "vscode-languageserver-types": {
+      "version": "3.16.0",
+      "resolved": "https://registry.npmjs.org/vscode-languageserver-types/-/vscode-languageserver-types-3.16.0.tgz",
+      "integrity": "sha512-k8luDIWJWyenLc5ToFQQMaSrqCHiLwyKPHKPQZ5zz21vM+vIVUSvsRpcbiECH4WR88K2XZqc4ScRcZ7nk/jbeA==",
+      "dev": true
+    },
+    "vscode-nls": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/vscode-nls/-/vscode-nls-5.0.0.tgz",
+      "integrity": "sha512-u0Lw+IYlgbEJFF6/qAqG2d1jQmJl0eyAGJHoAJqr2HT4M2BNuQYSEiSE75f52pXHSJm8AlTjnLLbBFPrdz2hpA==",
+      "dev": true
+    },
+    "vscode-uri": {
+      "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/vscode-uri/-/vscode-uri-3.0.2.tgz",
+      "integrity": "sha512-jkjy6pjU1fxUvI51P+gCsxg1u2n8LSt0W6KrCNQceaziKzff74GoWmjVG46KieVzybO1sttPQmYfrwSHey7GUA==",
+      "dev": true
+    },
     "watchpack": {
       "version": "2.2.0",
       "resolved": "https://registry.npmjs.org/watchpack/-/watchpack-2.2.0.tgz",

package.json

@@ -22,6 +22,7 @@
     "eslint-plugin-fetch-options": "^0.0.5",
     "eslint-plugin-html": "^6.1.2",
     "eslint-plugin-import": "^2.23.4",
+    "eslint-plugin-json": "^3.0.0",
     "eslint-plugin-mozilla": "^2.10.0",
     "eslint-plugin-no-unsanitized": "^3.1.5",
     "eslint-plugin-prettier": "^3.4.0",

test/types/tsconfig.json

@@ -22,5 +22,5 @@
   },
   "files": [
     "main.ts"
-  ],
+  ]
 }