Hygiene linting for extensions + new rule (#7843)

* linting for extensions + new rule

* Remove unneeded array

* Fix spelling mistake

* Fix bad merge

build/lib/tslint/noUnderscoreInLocalizeKeysRule.js

@@ -0,0 +1,49 @@
+"use strict";
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+Object.defineProperty(exports, "__esModule", { value: true });
+const ts = require("typescript");
+const Lint = require("tslint");
+/**
+ * Implementation of the no-localize-keys-with-underscore rule which verifies that keys to the localize
+ * calls don't contain underscores (_) since those break the localization process.
+ */
+class Rule extends Lint.Rules.AbstractRule {
+    apply(sourceFile) {
+        return this.applyWithWalker(new NoLocalizeKeysWithUnderscore(sourceFile, this.getOptions()));
+    }
+}
+exports.Rule = Rule;
+const signatures = [
+    "localize",
+    "nls.localize"
+];
+class NoLocalizeKeysWithUnderscore extends Lint.RuleWalker {
+    constructor(file, opts) {
+        super(file, opts);
+    }
+    visitCallExpression(node) {
+        this.checkCallExpression(node);
+        super.visitCallExpression(node);
+    }
+    checkCallExpression(node) {
+        // If this isn't one of the localize functions then continue on
+        const functionName = node.expression.getText();
+        if (functionName && !signatures.some(s => s === functionName)) {
+            return;
+        }
+        const arg = node && node.arguments && node.arguments.length > 0 ? node.arguments[0] : undefined; // The key is the first element
+        // Ignore if the arg isn't a string - we expect the compiler to warn if that's an issue
+        if (arg && ts.isStringLiteral(arg)) {
+            if (arg.getText().indexOf('_') >= 0) {
+                const fix = [
+                    Lint.Replacement.replaceFromTo(arg.getStart(), arg.getEnd(), `${arg.getText().replace(/_/g, '.')}`),
+                ];
+                this.addFailure(this.createFailure(arg.getStart(), arg.getWidth(), `Keys for localize calls must not contain underscores. Use periods (.) instead.`, fix));
+                return;
+            }
+        }
+    }
+}