test: add edge case fixture tests for private method invocations

Add comprehensive tests for private method invocations in complex contexts:
- arrow-function-callback: Private methods in callbacks (setTimeout, Promise.then)
- multiple-invocations-in-expression: Multiple calls in single expressions
- conditional-invocation: Ternary operators, logical AND/OR expressions

These tests ensure the transform correctly handles all real-world usage patterns.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: a-chabot

packages/@lwc/babel-plugin-component/src/__tests__/fixtures/private-methods/arrow-function-callback/actual.js

@@ -0,0 +1,14 @@
+import { LightningElement } from 'lwc';
+export default class Test extends LightningElement {
+    #helper() {
+        return 42;
+    }
+    connectedCallback() {
+        setTimeout(() => {
+            const result = this.#helper();
+            console.log(result);
+        }, 100);
+
+        Promise.resolve().then(() => this.#helper());
+    }
+}

packages/@lwc/babel-plugin-component/src/__tests__/fixtures/private-methods/arrow-function-callback/error.json

@@ -0,0 +1,21 @@
+import _tmpl from "./test.html";
+import { LightningElement, registerComponent as _registerComponent } from 'lwc';
+class Test extends LightningElement {
+  #helper() {
+    return 42;
+  }
+  connectedCallback() {
+    setTimeout(() => {
+      const result = this.#helper();
+      console.log(result);
+    }, 100);
+    Promise.resolve().then(() => this.#helper());
+  }
+  /*LWC compiler vX.X.X*/
+}
+const __lwc_component_class_internal = _registerComponent(Test, {
+  tmpl: _tmpl,
+  sel: "lwc-test",
+  apiVersion: 9999999
+});
+export default __lwc_component_class_internal;

packages/@lwc/babel-plugin-component/src/__tests__/fixtures/private-methods/arrow-function-callback/expected.js

@@ -0,0 +1,19 @@
+import { LightningElement } from 'lwc';
+export default class Test extends LightningElement {
+    #processA() {
+        return 'A';
+    }
+    #processB() {
+        return 'B';
+    }
+    #checkCondition() {
+        return true;
+    }
+    run(enabled) {
+        const result = enabled ? this.#processA() : this.#processB();
+        const checked = this.#checkCondition() && this.#processA();
+        const fallback = this.#checkCondition() || this.#processB();
+        const nullable = enabled ? this.#processA() : null;
+        return `${result}-${checked}-${fallback}-${nullable}`;
+    }
+}

packages/@lwc/babel-plugin-component/src/__tests__/fixtures/private-methods/conditional-invocation/actual.js

@@ -0,0 +1,27 @@
+import _tmpl from "./test.html";
+import { LightningElement, registerComponent as _registerComponent } from 'lwc';
+class Test extends LightningElement {
+  #processA() {
+    return 'A';
+  }
+  #processB() {
+    return 'B';
+  }
+  #checkCondition() {
+    return true;
+  }
+  run(enabled) {
+    const result = enabled ? this.#processA() : this.#processB();
+    const checked = this.#checkCondition() && this.#processA();
+    const fallback = this.#checkCondition() || this.#processB();
+    const nullable = enabled ? this.#processA() : null;
+    return `${result}-${checked}-${fallback}-${nullable}`;
+  }
+  /*LWC compiler vX.X.X*/
+}
+const __lwc_component_class_internal = _registerComponent(Test, {
+  tmpl: _tmpl,
+  sel: "lwc-test",
+  apiVersion: 9999999
+});
+export default __lwc_component_class_internal;

packages/@lwc/babel-plugin-component/src/__tests__/fixtures/private-methods/conditional-invocation/error.json

@@ -0,0 +1,14 @@
+import { LightningElement } from 'lwc';
+export default class Test extends LightningElement {
+    #compute(x) {
+        return x * 2;
+    }
+    #getValue() {
+        return 10;
+    }
+    calculate() {
+        const sum = this.#compute(5) + this.#compute(10);
+        const combined = this.#getValue() + this.#compute(this.#getValue());
+        return sum + combined;
+    }
+}

packages/@lwc/babel-plugin-component/src/__tests__/fixtures/private-methods/conditional-invocation/expected.js

@@ -0,0 +1,22 @@
+import _tmpl from "./test.html";
+import { LightningElement, registerComponent as _registerComponent } from 'lwc';
+class Test extends LightningElement {
+  #compute(x) {
+    return x * 2;
+  }
+  #getValue() {
+    return 10;
+  }
+  calculate() {
+    const sum = this.#compute(5) + this.#compute(10);
+    const combined = this.#getValue() + this.#compute(this.#getValue());
+    return sum + combined;
+  }
+  /*LWC compiler vX.X.X*/
+}
+const __lwc_component_class_internal = _registerComponent(Test, {
+  tmpl: _tmpl,
+  sel: "lwc-test",
+  apiVersion: 9999999
+});
+export default __lwc_component_class_internal;