feat: add allowProperties option to require-atomic-updates

docs/rules/require-atomic-updates.md

@@ -38,32 +38,50 @@ Promise.all([getPageLength(1), getPageLength(2)]).then(pageLengths => {
 
 ## Rule Details
 
-This rule aims to report assignments to variables or properties where all of the following are true:
+This rule aims to report assignments to variables or properties in cases where the assignments may be based on outdated values.
 
-* A variable or property is reassigned to a new value which is based on its old value.
-* A `yield` or `await` expression interrupts the assignment after the old value is read, and before the new value is set.
-* The rule cannot easily verify that the assignment is safe (e.g. if an assigned variable is local and would not be readable from anywhere else while the function is paused).
+### Variables
+
+This rule reports an assignment to a variable when it detects the following execution flow in a generator or async function:
+
+1. The variable is read.
+2. A `yield` or `await` pauses the function.
+3. After the function is resumed, a value is assigned to the variable.
+
+The assignment in step 3 is reported because this flow indicates that the assignment is based on the possibly outdated value of the variable from step 1, as the variable may have been reassigned elsewhere while the function was paused in step 2.
+
+Note that the rule does not report the aforementioned assignment in any of the following cases:
+
+* If the variable is read again between steps 2 and 3.
+* If the variable cannot be accessed while the function is paused (e.g., if it's a local variable).
 
 Examples of **incorrect** code for this rule:
 
 ```js
 /* eslint require-atomic-updates: error */
 
 let result;
-async function foo() {
-  result += await somethingElse;
 
-  result = result + await somethingElse;
+async function foo() {
+    result += await something;
+}
 
-  result = result + doSomething(await somethingElse);
+async function bar() {
+    result = result + await something;
 }
 
-function* bar() {
-  result += yield;
+async function baz() {
+    result = result + doSomething(await somethingElse);
+}
 
-  result = result + (yield somethingElse);
+async function qux() {
+    if (!result) {
+        result = await initialize();
+    }
+}
 
-  result = result + doSomething(yield somethingElse);
+function* generator() {
+    result += yield;
 }
 ```
 
@@ -73,22 +91,89 @@ Examples of **correct** code for this rule:
 /* eslint require-atomic-updates: error */
 
 let result;
-async function foo() {
-  result = await somethingElse + result;
 
-  let tmp = await somethingElse;
-  result += tmp;
+async function foobar() {
+    result = await something + result;
+}
+
+async function baz() {
+    const tmp = doSomething(await somethingElse);
+    result += tmp;
+}
+
+async function qux() {
+    if (!result) {
+        const tmp = await initialize();
+        if (!result) {
+            result = tmp;
+        }
+    }
+}
+
+async function quux() {
+    let localVariable = 0;
+    localVariable += await something;
+}
+
+function* generator() {
+    result = (yield) + result;
+}
+```
+
+### Properties
+
+This rule reports an assignment to a property through a variable when it detects the following execution flow in a generator or async function:
+
+1. The variable is read. This can be reading a property through the variable.
+2. A `yield` or `await` pauses the function.
+3. After the function is resumed, a value is assigned to a property through the variable.
 
-  let localVariable = 0;
-  localVariable += await somethingElse;
+This logic is similar to the logic for variables, but stricter because the property in step 3 doesn't have to be the same as the property in step 1. It is assumed that the flow depends on the state of the object as a whole.
+
+Example of **incorrect** code for this rule:
+
+```js
+/* eslint require-atomic-updates: error */
+
+async function foo(obj) {
+    if (!obj.done) {
+        obj.something = await getSomething();
+    }
 }
+```
 
-function* bar() {
-  result = (yield) + result;
+Example of **correct** code for this rule:
 
-  result = (yield somethingElse) + result;
+```js
+/* eslint require-atomic-updates: error */
+
+async function foo(obj) {
+    if (!obj.done) {
+        const tmp = await getSomething();
+        if (!obj.done) {
+            obj.something = tmp;
+        }
+    }
+}
+```
+
+## Options
+
+This rule has an object option:
+
+* `"allowProperties"`: When set to `true`, the rule does not report assignments to properties. Default is `false`.
+
+### allowProperties
+
+Example of **correct** code for this rule with the `{ "allowProperties": true }` option:
+
+```js
+/* eslint require-atomic-updates: ["error", { "allowProperties": true }] */
 
-  result = doSomething(yield somethingElse, result);
+async function foo(obj) {
+    if (!obj.done) {
+        obj.something = await getSomething();
+    }
 }
 ```
 

lib/rules/require-atomic-updates.js

@@ -176,7 +176,17 @@ module.exports = {
         },
 
         fixable: null,
-        schema: [],
+
+        schema: [{
+            type: "object",
+            properties: {
+                allowProperties: {
+                    type: "boolean",
+                    default: false
+                }
+            },
+            additionalProperties: false
+        }],
 
         messages: {
             nonAtomicUpdate: "Possible race condition: `{{value}}` might be reassigned based on an outdated value of `{{value}}`.",
@@ -185,6 +195,8 @@ module.exports = {
     },
 
     create(context) {
+        const allowProperties = !!context.options[0] && context.options[0].allowProperties;
+
         const sourceCode = context.getSourceCode();
         const assignmentReferences = new Map();
         const segmentInfo = new SegmentInfo();
@@ -284,7 +296,7 @@ module.exports = {
                                         value: variable.name
                                     }
                                 });
-                            } else {
+                            } else if (!allowProperties) {
                                 context.report({
                                     node: node.parent,
                                     messageId: "nonAtomicObjectUpdate",

tests/lib/rules/require-atomic-updates.js

@@ -214,7 +214,29 @@ ruleTester.run("require-atomic-updates", rule, {
                 await a;
                 b = 1;
             }
-        `
+        `,
+
+        // allowProperties
+        {
+            code: `
+                async function a(foo) {
+                    if (foo.bar) {
+                        foo.bar = await something;
+                    }
+                }
+            `,
+            options: [{ allowProperties: true }]
+        },
+        {
+            code: `
+                function* g(foo) {
+                    baz = foo.bar;
+                    yield something;
+                    foo.bar = 1;
+                }
+            `,
+            options: [{ allowProperties: true }]
+        }
     ],
 
     invalid: [
@@ -358,6 +380,99 @@ ruleTester.run("require-atomic-updates", rule, {
                     line: 8
                 }
             ]
+        },
+
+        // allowProperties
+        {
+            code: `
+                async function a(foo) {
+                    if (foo.bar) {
+                        foo.bar = await something;
+                    }
+                }
+            `,
+            errors: [STATIC_PROPERTY_ERROR]
+        },
+        {
+            code: `
+                function* g(foo) {
+                    baz = foo.bar;
+                    yield something;
+                    foo.bar = 1;
+                }
+            `,
+            errors: [STATIC_PROPERTY_ERROR]
+        },
+        {
+            code: `
+                async function a(foo) {
+                    if (foo.bar) {
+                        foo.bar = await something;
+                    }
+                }
+            `,
+            options: [{}],
+            errors: [STATIC_PROPERTY_ERROR]
+
+        },
+        {
+            code: `
+                function* g(foo) {
+                    baz = foo.bar;
+                    yield something;
+                    foo.bar = 1;
+                }
+            `,
+            options: [{}],
+            errors: [STATIC_PROPERTY_ERROR]
+        },
+        {
+            code: `
+                async function a(foo) {
+                    if (foo.bar) {
+                        foo.bar = await something;
+                    }
+                }
+            `,
+            options: [{ allowProperties: false }],
+            errors: [STATIC_PROPERTY_ERROR]
+
+        },
+        {
+            code: `
+                function* g(foo) {
+                    baz = foo.bar;
+                    yield something;
+                    foo.bar = 1;
+                }
+            `,
+            options: [{ allowProperties: false }],
+            errors: [STATIC_PROPERTY_ERROR]
+        },
+        {
+            code: `
+                let foo;
+                async function a() {
+                    if (foo) {
+                        foo = await something;
+                    }
+                }
+            `,
+            options: [{ allowProperties: true }],
+            errors: [VARIABLE_ERROR]
+
+        },
+        {
+            code: `
+                let foo;
+                function* g() {
+                    baz = foo;
+                    yield something;
+                    foo = 1;
+                }
+            `,
+            options: [{ allowProperties: true }],
+            errors: [VARIABLE_ERROR]
         }
     ]
 });