prefer-to-be-null TypeError with TSAsExpression

[KaelWD]

ESLint: 6.1.0
@typescript-eslint/parser: 1.12.0
eslint-plugin-jest: 22.12.0

Code:

(expect('Model must be bound to an array if the multiple property is true') as any).toHaveBeenTipped()

Error in methodName:

TypeError: Cannot read property 'name' of undefined
Occurred while linting /home/kael/Documents/vuetifyjs/vuetify/packages/vuetify/src/components/VItemGroup/__tests__/VItemGroup.spec.ts:53
    at methodName (/home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint-plugin-jest/lib/rules/util.js:70:12)
    at expectNotCase (/home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint-plugin-jest/lib/rules/util.js:23:101)
    at expectToBeCase (/home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint-plugin-jest/lib/rules/util.js:43:41)
    at CallExpression (/home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint-plugin-jest/lib/rules/prefer-to-be-null.js:25:45)
    at /home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint/lib/linter/safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (/home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint/lib/linter/safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (/home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint/lib/linter/node-event-generator.js:253:26)
    at NodeEventGenerator.applySelectors (/home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint/lib/linter/node-event-generator.js:282:22)
    at NodeEventGenerator.enterNode (/home/kael/Documents/vuetifyjs/vuetify/node_modules/eslint/lib/linter/node-event-generator.js:296:14)

node.parent.property is undefined

[SimenB]

Thanks for the report!

This really shows how bad our current utilities are... I tried to fix this quickly, but I was unable to do so in a generic way, which means that while stopping this specific instance from crashing, other rules will probably crash in the same way as well. For now, I'd advise you to add an eslint-ignore comment, and I'll revisit this after the TS migration (#256) is complete. At that point, our helpers should be way safer and we can properly deal with this case

[G-Rath]

Bamn - TS conversion fixed this.

Do we want to add a test case for this?

It's a generic problem, and in order to have a test for it we'll have to set the parser for RuleTester to RuleTester parser to be set to @typescript-eslint/parser, b/c of the as:

const ruleTester = new TSESLint.RuleTester({
  parserOptions: { ecmaVersion: 2015 },
  parser: '@typescript-eslint/parser',
});

If we want a test case, I think ideally it should be added to the "standard tests" object I'm going to look to make, in which case all tests should be run using @typescript-eslint/parser.

I've got no problem w/ this, but don't know what the impacts to performance & co might be 😂

[SimenB]

Do we want to add a test case for this?

Yes :)

We can have a separate RuleTester for these ones in the same test file. I'd like to keep most tests with the default parser

[G-Rath]

Here's the fix

Index: src/rules/prefer-to-be-undefined.ts
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- src/rules/prefer-to-be-undefined.ts	(revision ca5370e9d3cd7dca22e04e8754e0472466439564)
+++ src/rules/prefer-to-be-undefined.ts	(date 1564984641177)
@@ -6,6 +6,7 @@
   ParsedEqualityMatcherCall,
   ParsedExpectMatcher,
   createRule,
+  followTypeAssertionChain,
   isExpectCall,
   isParsedEqualityMatcherCall,
   parseExpectCall,
@@ -32,7 +33,7 @@
   matcher: ParsedExpectMatcher,
 ): matcher is ParsedEqualityMatcherCall<UndefinedIdentifier> =>
   isParsedEqualityMatcherCall(matcher) &&
-  isUndefinedIdentifier(matcher.arguments[0]);
+  isUndefinedIdentifier(followTypeAssertionChain(matcher.arguments[0]));
 
 export default createRule({
   name: __filename,
Index: src/rules/prefer-to-be-null.ts
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- src/rules/prefer-to-be-null.ts	(revision ca5370e9d3cd7dca22e04e8754e0472466439564)
+++ src/rules/prefer-to-be-null.ts	(date 1564984599869)
@@ -3,9 +3,11 @@
   TSESTree,
 } from '@typescript-eslint/experimental-utils';
 import {
+  MaybeTypeCast,
   ParsedEqualityMatcherCall,
   ParsedExpectMatcher,
   createRule,
+  followTypeAssertionChain,
   isExpectCall,
   isParsedEqualityMatcherCall,
   parseExpectCall,
@@ -24,12 +26,13 @@
  *
  * @param {ParsedExpectMatcher} matcher
  *
- * @return {matcher is ParsedNullEqualityMatcher}
+ * @return {matcher is ParsedEqualityMatcherCall<MaybeTypeCast<NullLiteral>>}
  */
 const isNullEqualityMatcher = (
   matcher: ParsedExpectMatcher,
-): matcher is ParsedEqualityMatcherCall<NullLiteral> =>
-  isParsedEqualityMatcherCall(matcher) && isNullLiteral(matcher.arguments[0]);
+): matcher is ParsedEqualityMatcherCall<MaybeTypeCast<NullLiteral>> =>
+  isParsedEqualityMatcherCall(matcher) &&
+  isNullLiteral(followTypeAssertionChain(matcher.arguments[0]));
 
 export default createRule({
   name: __filename,
Index: src/rules/__tests__/prefer-to-be-undefined.test.ts
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- src/rules/__tests__/prefer-to-be-undefined.test.ts	(revision ca5370e9d3cd7dca22e04e8754e0472466439564)
+++ src/rules/__tests__/prefer-to-be-undefined.test.ts	(date 1564951416912)
@@ -40,3 +40,23 @@
     },
   ],
 });
+
+new TSESLint.RuleTester({
+  parser: '@typescript-eslint/parser',
+}).run('prefer-to-be-undefined: typescript edition', rule, {
+  valid: [
+    "(expect('Model must be bound to an array if the multiple property is true') as any).toHaveBeenTipped()",
+  ],
+  invalid: [
+    {
+      code: 'expect(undefined).toBe(undefined as unknown as string as any);',
+      errors: [{ messageId: 'useToBeUndefined', column: 19, line: 1 }],
+      output: 'expect(undefined).toBeUndefined();',
+    },
+    {
+      code: 'expect("a string").not.toEqual(undefined as number);',
+      errors: [{ messageId: 'useToBeUndefined', column: 24, line: 1 }],
+      output: 'expect("a string").not.toBeUndefined();',
+    },
+  ],
+});
Index: src/rules/__tests__/prefer-to-be-null.test.ts
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- src/rules/__tests__/prefer-to-be-null.test.ts	(revision ca5370e9d3cd7dca22e04e8754e0472466439564)
+++ src/rules/__tests__/prefer-to-be-null.test.ts	(date 1564984722414)
@@ -43,3 +43,23 @@
     },
   ],
 });
+
+new TSESLint.RuleTester({
+  parser: '@typescript-eslint/parser',
+}).run('prefer-to-be-null: typescript edition', rule, {
+  valid: [
+    "(expect('Model must be bound to an array if the multiple property is true') as any).toHaveBeenTipped()",
+  ],
+  invalid: [
+    {
+      code: 'expect(null).toBe(null as unknown as string as unknown as any);',
+      errors: [{ messageId: 'useToBeNull', column: 14, line: 1 }],
+      output: 'expect(null).toBeNull();',
+    },
+    {
+      code: 'expect("a string").not.toEqual(null as number);',
+      errors: [{ messageId: 'useToBeNull', column: 24, line: 1 }],
+      output: 'expect("a string").not.toBeNull();',
+    },
+  ],
+});
Index: src/rules/utils.ts
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- src/rules/utils.ts	(revision ca5370e9d3cd7dca22e04e8754e0472466439564)
+++ src/rules/utils.ts	(date 1564984544619)
@@ -14,6 +14,35 @@
   return `${REPO_URL}/blob/v${version}/docs/rules/${ruleName}.md`;
 });
 
+export type MaybeTypeCast<Expression extends TSESTree.Expression> =
+  | TSTypeCastExpression<Expression>
+  | Expression;
+
+export type TSTypeCastExpression<
+  Expression extends TSESTree.Expression = TSESTree.Expression
+> = AsExpressionChain<Expression> | TypeAssertionChain<Expression>;
+
+interface AsExpressionChain<
+  Expression extends TSESTree.Expression = TSESTree.Expression
+> extends TSESTree.TSAsExpression {
+  expression: AsExpressionChain<Expression> | Expression;
+}
+
+interface TypeAssertionChain<
+  Expression extends TSESTree.Expression = TSESTree.Expression
+> extends TSESTree.TSTypeAssertion {
+  // expression: TypeAssertionChain<Expression> | Expression;
+  expression: any; // https://github.com/typescript-eslint/typescript-eslint/issues/802
+}
+
+export const followTypeAssertionChain = (
+  expression: TSESTree.Expression | TSTypeCastExpression,
+): TSESTree.Expression =>
+  expression.type === AST_NODE_TYPES.TSAsExpression ||
+  expression.type === AST_NODE_TYPES.TSTypeAssertion
+    ? followTypeAssertionChain(expression.expression)
+    : expression;
+
 /**
  * A `Literal` with a `value` of type `string`.
  */

I'll make a PR once #363 is merged

The takeaway is that:

• Casts are to expression nodes as MemberExpressions are to expect() CallExpections: they make a chain leading down to the actual value that's being cast,
• When working w/ arguments (among other things) we should consider what if they're being cast
  • Typically rules that are working on argument raw values such as prefer-to-be-undefined & prefer-to-be-null we should ignore the cast in favor of whatever the actual value is.
• followTypeAssertionChain will return the final node in the cast chain, and should be usable for most general cases w/o worry.

This raises the question of what to do w/ prefer-to-contain, as it checks for a boolean literal.
I think for consistency it should probably also use followTypeAssertionChain, b/c why would you cast a boolean type anyway...?

[SimenB]

@G-Rath can we fix this now?

[G-Rath]

@SimenB Sure can! #403 has got your back.

Sorry for the delay - a few things popped up that stole my attention, combined w/ tackling no-untrimmed-title 😬

[SimenB]

🎉 This issue has been resolved in version 22.15.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀