feat(linter/typescript/no-unneccessary-condition): add rule

Author: camc314

apps/oxlint/fixtures/tsgolint/.oxlintrc.json

@@ -17,6 +17,7 @@
     "typescript/no-mixed-enums": "error",
     "typescript/no-redundant-type-constituents": "error",
     "typescript/no-unnecessary-boolean-literal-compare": "error",
+    "typescript/no-unnecessary-condition": "error",
     "typescript/no-unnecessary-template-expression": "error",
     "typescript/no-unnecessary-type-arguments": "error",
     "typescript/no-unnecessary-type-assertion": "error",

apps/oxlint/fixtures/tsgolint/no-unneccessary-condition.ts

@@ -0,0 +1,3 @@
+declare const b1: object;
+declare const b2: boolean;
+export const t1 = b1 && b2;

apps/oxlint/fixtures/tsgolint_rule_options/.oxlintrc.json

@@ -44,6 +44,14 @@
         "allowOptionalChaining": true
       }
     ],
+    "typescript/no-unnecessary-condition": [
+      "error",
+      {
+        "allowConstantLoopConditions": true,
+        "checkTypePredicates": false,
+        "allowRuleToRunWithoutStrictNullChecksIKnowWhatIAmDoing": false
+      }
+    ],
     "typescript/only-throw-error": [
       "error",
       {

apps/oxlint/fixtures/tsgolint_rule_options/test.ts

@@ -62,6 +62,18 @@ declare const unknownValue: unknown;
 // This SHOULD error because checkUnknown is true
 const unknownStr = unknownValue.toString();
 
+// Test no-unnecessary-condition with allowConstantLoopConditions option
+declare const alwaysTruthyObject: object;
+// This SHOULD error because this object is always truthy
+if (alwaysTruthyObject) {
+  result += 1;
+}
+
+// This should NOT error because allowConstantLoopConditions is true
+while (true) {
+  break;
+}
+
 // Test only-throw-error with allowRethrowing option
 // When allowRethrowing is false, rethrowing a caught error SHOULD error
 try {

apps/oxlint/src/snapshots/fixtures__tsgolint_--type-aware --silent@oxlint.snap

@@ -6,8 +6,8 @@ arguments: --type-aware --silent
 working directory: fixtures/tsgolint
 ----------
 
-Found 0 warnings and 52 errors.
-Finished in <variable>ms on 46 files with 45 rules using 1 threads.
+Found 0 warnings and 57 errors.
+Finished in <variable>ms on 47 files with 46 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__tsgolint_--type-aware -c config-test.json@oxlint.snap

@@ -40,7 +40,7 @@ working directory: fixtures/tsgolint
   help: Remove the debugger statement
 
 Found 2 warnings and 2 errors.
-Finished in <variable>ms on 46 files with 1 rules using 1 threads.
+Finished in <variable>ms on 47 files with 1 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__tsgolint_--type-aware test.svelte@oxlint.snap

@@ -16,7 +16,7 @@ working directory: fixtures/tsgolint
   help: Remove the debugger statement
 
 Found 0 warnings and 1 error.
-Finished in <variable>ms on 1 file with 45 rules using 1 threads.
+Finished in <variable>ms on 1 file with 46 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__tsgolint_--type-aware@oxlint.snap

@@ -126,6 +126,20 @@ working directory: fixtures/tsgolint
    :                    ^^^^^^^
    `----
 
+  x typescript-eslint(no-unnecessary-condition): Unnecessary conditional, value is always truthy.
+   ,-[no-unneccessary-condition.ts:3:19]
+ 2 | declare const b2: boolean;
+ 3 | export const t1 = b1 && b2;
+   :                   ^^
+   `----
+
+  x typescript-eslint(strict-boolean-expressions): Unexpected object value in conditional. An object is always truthy.
+   ,-[no-unneccessary-condition.ts:3:19]
+ 2 | declare const b2: boolean;
+ 3 | export const t1 = b1 && b2;
+   :                   ^^
+   `----
+
   x typescript-eslint(no-unnecessary-boolean-literal-compare): This expression unnecessarily compares a boolean value to a boolean instead of using it directly.
    ,-[no-unnecessary-boolean-literal-compare.ts:2:5]
  1 | declare const someCondition: boolean;
@@ -181,6 +195,14 @@ working directory: fixtures/tsgolint
  3 | 
    `----
 
+  x typescript-eslint(no-unnecessary-condition): Unnecessary comparison between literal values.
+    ,-[no-unsafe-enum-comparison.ts:9:20]
+  8 | }
+  9 | const comparison = Status.Open === Color.Red;
+    :                    ^^^^^^^^^^^^^^^^^^^^^^^^^
+ 10 | 
+    `----
+
   x typescript-eslint(no-unsafe-enum-comparison): The two values in this comparison do not have a shared enum type.
     ,-[no-unsafe-enum-comparison.ts:9:20]
   8 | }
@@ -283,6 +305,13 @@ working directory: fixtures/tsgolint
    :                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    `----
 
+  x typescript-eslint(no-unnecessary-condition): This condition will always return the same value since the types have no overlap.
+   ,-[prefer-nullish-coalescing.ts:2:50]
+ 1 | declare const nullableString: string | null;
+ 2 | const nullishResult = nullableString !== null && nullableString !== undefined ? nullableString : 'default';
+   :                                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   `----
+
   x typescript-eslint(prefer-optional-chain): Prefer using an optional chain expression instead, as it's more concise and easier to read.
    ,-[prefer-optional-chain.ts:3:1]
  2 | declare const fooOptC: { bar: number } | null | undefined;
@@ -381,6 +410,14 @@ working directory: fixtures/tsgolint
  3 | 
    `----
 
+  x typescript-eslint(no-unnecessary-condition): Unnecessary conditional, value is always truthy.
+   ,-[strict-boolean-expressions.ts:2:5]
+ 1 | const str = 'hello';
+ 2 | if (str) {
+   :     ^^^
+ 3 | }
+   `----
+
   x typescript-eslint(switch-exhaustiveness-check): Switch is not exhaustive
    ,-[switch-exhaustiveness-check.ts:3:11]
  2 | function handleStatus(status: Status) {
@@ -406,8 +443,8 @@ working directory: fixtures/tsgolint
    :                   ^^^^^^^^
    `----
 
-Found 0 warnings and 52 errors.
-Finished in <variable>ms on 46 files with 45 rules using 1 threads.
+Found 0 warnings and 57 errors.
+Finished in <variable>ms on 47 files with 46 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__tsgolint_rule_options_--type-aware@oxlint.snap

@@ -40,8 +40,16 @@ working directory: fixtures/tsgolint_rule_options
     `----
   help: Consider picking a property (e.g. `user.name`), using a formatter (or `JSON.stringify`), or implementing a custom `toString()`/`toLocaleString()` on the type.
 
-Found 0 warnings and 4 errors.
-Finished in <variable>ms on 1 file with 7 rules using 1 threads.
+  x typescript-eslint(no-unnecessary-condition): Unnecessary conditional, value is always truthy.
+    ,-[test.ts:68:5]
+ 67 | // This SHOULD error because this object is always truthy
+ 68 | if (alwaysTruthyObject) {
+    :     ^^^^^^^^^^^^^^^^^^
+ 69 |   result += 1;
+    `----
+
+Found 0 warnings and 5 errors.
+Finished in <variable>ms on 1 file with 8 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------