Include the root package.json file in the linting

This commit also moves the npm-package-json-lint config to the standalone file.

.npmpackagejsonlintrc.json

@@ -0,0 +1,39 @@
+{
+	"extends": "@wordpress/npm-package-json-lint-config",
+	"rules": {
+		"description-format": [
+			"error",
+			{
+				"requireCapitalFirstLetter": true,
+				"requireEndingPeriod": true
+			}
+		],
+		"prefer-no-devDependencies": "error",
+		"require-publishConfig": "error",
+		"require-repository-directory": "error",
+		"valid-values-author": [
+			"error",
+			[
+				"The WordPress Contributors"
+			]
+		],
+		"valid-values-publishConfig": [
+			"error",
+			[
+				{
+					"access": "public"
+				}
+			]
+		]
+	},
+	"overrides": [
+		{
+			"patterns": [ "./package.json" ],
+			"rules": {
+				"require-publishConfig": "off",
+				"require-repository-directory": "off",
+				"prefer-no-devDependencies": "off"
+			}
+		}
+	]
+}

package.json

@@ -156,35 +156,6 @@
 		"webpack": "4.41.0",
 		"worker-farm": "1.7.0"
 	},
-	"npmpackagejsonlint": {
-		"extends": "@wordpress/npm-package-json-lint-config",
-		"rules": {
-			"description-format": [
-				"error",
-				{
-					"requireCapitalFirstLetter": true,
-					"requireEndingPeriod": true
-				}
-			],
-			"prefer-no-devDependencies": "error",
-			"require-publishConfig": "error",
-			"require-repository-directory": "error",
-			"valid-values-author": [
-				"error",
-				[
-					"The WordPress Contributors"
-				]
-			],
-			"valid-values-publishConfig": [
-				"error",
-				[
-					{
-						"access": "public"
-					}
-				]
-			]
-		}
-	},
 	"scripts": {
 		"prebuild": "npm run check-engines",
 		"clean:packages": "rimraf ./packages/*/build ./packages/*/build-module ./packages/*/build-style ./packages/*/node_modules",
@@ -207,7 +178,7 @@
 		"lint-js": "wp-scripts lint-js",
 		"lint-js:fix": "npm run lint-js -- --fix",
 		"lint-php": "wp-scripts env lint-php",
-		"lint-pkg-json": "wp-scripts lint-pkg-json 'packages/*/package.json'",
+		"lint-pkg-json": "wp-scripts lint-pkg-json . 'packages/*/package.json'",
 		"lint-css": "wp-scripts lint-style '**/*.scss'",
 		"lint-css:fix": "npm run lint-css -- --fix",
 		"lint-types": "tsc",

packages/scripts/scripts/lint-pkg-json.js

@@ -25,7 +25,9 @@ const hasLintConfig = hasArgInCLI( '-c' ) ||
 	hasArgInCLI( '--configFile' ) ||
 	hasProjectFile( '.npmpackagejsonlintrc.json' ) ||
 	hasProjectFile( 'npmpackagejsonlint.config.js' ) ||
-	hasPackageProp( 'npmpackagejsonlint' );
+	hasPackageProp( 'npmpackagejsonlint' ) ||
+	// npm-package-json-lint v3.x used a different prop name.
+	hasPackageProp( 'npmPackageJsonLintConfig' );
 
 const defaultConfigArgs = ! hasLintConfig ?
 	[ '--configFile', fromConfigRoot( 'npmpackagejsonlint.json' ) ] :