tools,test: enforce assert.ifError with lint rule

This adds an ESLint rule to enforce the use of `assert.ifError(err)`
instead of `if (err) throw err;` in tests.

PR-URL: https://github.com/nodejs/node/pull/10671
Ref: https://github.com/nodejs/node/pull/10543
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Michal Zasso <targos@protonmail.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/tools/eslint-rules/prefer-assert-iferror.js b/tools/eslint-rules/prefer-assert-iferror.js
new file mode 100644
index 0000000000..0da272d5f6
--- /dev/null
+++ b/tools/eslint-rules/prefer-assert-iferror.js
@@ -0,0 +1,42 @@
+/**
+ * @fileoverview Prohibit the `if (err) throw err;` pattern
+ * @author Teddy Katz
+ */
+
+'use strict';
+
+module.exports = {
+  create(context) {
+    const sourceCode = context.getSourceCode();
+
+    function hasSameTokens(nodeA, nodeB) {
+      const aTokens = sourceCode.getTokens(nodeA);
+      const bTokens = sourceCode.getTokens(nodeB);
+
+      return aTokens.length === bTokens.length &&
+        aTokens.every((token, index) => {
+          return token.type === bTokens[index].type &&
+            token.value === bTokens[index].value;
+        });
+    }
+
+    return {
+      IfStatement(node) {
+        const firstStatement = node.consequent.type === 'BlockStatement' ?
+          node.consequent.body[0] :
+          node.consequent;
+        if (
+          firstStatement &&
+          firstStatement.type === 'ThrowStatement' &&
+          hasSameTokens(node.test, firstStatement.argument)
+        ) {
+          context.report({
+            node: firstStatement,
+            message: 'Use assert.ifError({{argument}}) instead.',
+            data: {argument: sourceCode.getText(node.test)}
+          });
+        }
+      }
+    };
+  }
+};