Implement first custom linter rule async-suffix

2 files changed, 33 insertions, 0 deletions

diff --git a/packages/tslint-config/rules/asyncSuffixRule.ts b/packages/tslint-config/rules/asyncSuffixRule.ts
new file mode 100644
index 000000000..c6ae5189c
--- /dev/null
+++ b/packages/tslint-config/rules/asyncSuffixRule.ts
@@ -0,0 +1,10 @@
+import * as Lint from 'tslint';
+import * as ts from 'typescript';
+
+import {AsyncSuffixWalker} from './walkers/async_suffix';
+
+export class Rule extends Lint.Rules.AbstractRule {
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithWalker(new AsyncSuffixWalker(sourceFile, this.getOptions()));
+    }
+}
diff --git a/packages/tslint-config/rules/walkers/async_suffix.ts b/packages/tslint-config/rules/walkers/async_suffix.ts
new file mode 100644
index 000000000..0c89bd99f
--- /dev/null
+++ b/packages/tslint-config/rules/walkers/async_suffix.ts
@@ -0,0 +1,23 @@
+import * as _ from 'lodash';
+import * as Lint from 'tslint';
+import * as ts from 'typescript';
+
+export class AsyncSuffixWalker extends Lint.RuleWalker {
+    public static FAILURE_STRING = 'async functions must have an Async suffix';
+    public visitMethodDeclaration(node: ts.MethodDeclaration): void {
+        const methodNameNode = node.name;
+        const methodName = methodNameNode.getText();
+        if (!_.isUndefined(node.type)) {
+            if (node.type.kind === ts.SyntaxKind.TypeReference) {
+                const returnTypeName = (node.type as ts.TypeReferenceNode).typeName.getText();
+                if (returnTypeName === 'Promise' && !methodName.endsWith('Async')) {
+                    const failure = this.createFailure(
+                        methodNameNode.getStart(), methodNameNode.getWidth(), AsyncSuffixWalker.FAILURE_STRING,
+                    );
+                    this.addFailure(failure);
+                }
+            }
+        }
+        super.visitMethodDeclaration(node);
+    }
+}