Analysis: Convert compose view model guideline to konsist

This commit demonstrates how an existing documented Compose guideline
can be easily converted to Konstist, and, at the same time showcases how
adding a KDoc on top of this custom test/rule make this a living
document.

WooCommerce/src/main/kotlin/com/woocommerce/android/ui/woopos/home/cart/WooPosCartScreen.kt

@@ -74,9 +74,10 @@ import com.woocommerce.android.ui.woopos.common.composeui.designsystem.WooPosTyp
 import com.woocommerce.android.ui.woopos.common.composeui.designsystem.toAdaptivePadding
 
 @Composable
-fun WooPosCartScreen(modifier: Modifier = Modifier) {
-    val viewModel: WooPosCartViewModel = hiltViewModel()
-
+fun WooPosCartScreen(
+    modifier: Modifier = Modifier,
+    viewModel: WooPosCartViewModel = hiltViewModel()
+) {
     viewModel.state.observeAsState().value?.let {
         WooPosCartScreen(modifier, it, viewModel::onUIEvent)
     }

libs/konsist-tests/src/test/java/com/woocommerce/android/konsist/test/KonsistComposeTest.kt

@@ -1,11 +1,13 @@
 package com.woocommerce.android.konsist.test
 
+import androidx.compose.runtime.Composable
 import androidx.compose.ui.tooling.preview.Preview
 import com.lemonappdev.konsist.api.Konsist
 import com.lemonappdev.konsist.api.ext.list.withAnnotationOf
 import com.lemonappdev.konsist.api.verify.assertTrue
 import org.junit.Test
 
+@Suppress("MaxLineLength")
 class KonsistComposeTest {
     @Test
     fun `all jetpack compose previews contain 'preview' in method name`() {
@@ -14,4 +16,39 @@ class KonsistComposeTest {
             .withAnnotationOf(Preview::class)
             .assertTrue { it.hasNameContaining("Preview") }
     }
+
+    /**
+     * [Composable Functions Best Practices ✅](https://github.com/woocommerce/woocommerce-android/blob/trunk/docs/compose.md#composable-functions-best-practices--)
+     *
+     * Don't acquire the viewModel inside a composable function, this will make testing harder. Inject it as a parameter
+     * and provide a default value to facilitate reusability:
+     *
+     * ❌
+     *
+     * ```
+     * @Composable
+     * fun MyComposable() {
+     * 	val viewModel by viewModel<MyViewModel>()
+     * 	...
+     * }
+     * ```
+     *
+     * ✅
+     *
+     * ```
+     * @Composable
+     * fun MyComposable(viewModel : MyViewModel = getViewModel()) {
+     * 	...
+     * }
+     * ```
+     */
+    @Test
+    fun `composable functions should not acquire view model directly`() {
+        Konsist.scopeFromProject()
+            .functions()
+            .withAnnotationOf(Composable::class)
+            .assertTrue { function ->
+                !function.text.contains("""(?i)val\s+\w*viewModel""".toRegex())
+            }
+    }
 }