docs(core): add continuous task to task pipeline and project config pages (#30919)

This PR adds information about `continuous` option for tasks. Also
removes references to Nx <16 examples on the project configuration page.

**Preview:**
-
https://nx-dev-git-docs-continuous-tasks-nrwl.vercel.app/recipes/running-tasks/defining-task-pipeline#continuous-task-dependencies
- Add a section on continuous task and links to the project
configuration reference page (below)
-
https://nx-dev-git-docs-continuous-tasks-nrwl.vercel.app/reference/project-configuration#continuous
- Add section on continuous task with example of `e2e -> serve`
dependency
- Add a callout on `dependsOn` section for continuous/long-running tasks
(long-running is mentioned so it appears in the search)
  - Remove Nx <16 examples

**TODO:**
- [x] Update PDV that show e2e and serve targets

docs/shared/concepts/myreactapp.json

@@ -29,7 +29,8 @@
         "serve": {
           "options": {
             "cwd": "apps/myreactapp",
-            "command": "vite serve"
+            "command": "vite serve",
+            "continuous": true
           },
           "executor": "nx:run-commands",
           "configurations": {},
@@ -51,7 +52,8 @@
         "serve-static": {
           "executor": "@nx/web:file-server",
           "options": {
-            "buildTarget": "build"
+            "buildTarget": "build",
+            "continuous": true
           },
           "configurations": {}
         },

docs/shared/migration/adding-to-existing-project.md

@@ -169,7 +169,8 @@ nx show project my-workspace --web
         "dev": {
           "options": {
             "cwd": ".",
-            "command": "next dev"
+            "command": "next dev",
+            "continuous": true
           },
           "executor": "nx:run-commands",
           "configurations": {},
@@ -180,7 +181,8 @@ nx show project my-workspace --web
         "start": {
           "options": {
             "cwd": ".",
-            "command": "next start"
+            "command": "next start",
+            "continuous": true
           },
           "dependsOn": ["build"],
           "executor": "nx:run-commands",

docs/shared/migration/adding-to-monorepo.md

@@ -165,7 +165,8 @@ nx show project my-workspace --web
         "dev": {
           "options": {
             "cwd": ".",
-            "command": "next dev"
+            "command": "next dev",
+            "continuous": true
           },
           "executor": "nx:run-commands",
           "configurations": {},
@@ -176,7 +177,8 @@ nx show project my-workspace --web
         "start": {
           "options": {
             "cwd": ".",
-            "command": "next start"
+            "command": "next start",
+            "continuous": true
           },
           "dependsOn": ["build"],
           "executor": "nx:run-commands",

docs/shared/recipes/running-tasks/convert-to-inferred.md

@@ -84,7 +84,8 @@ For example, if we migrated the `@nx/vite` plugin for a single app (i.e. `nx g @
         "serve": {
           "executor": "nx:run-commands",
           "options": {
-            "command": "vite dev"
+            "command": "vite dev",
+            "continuous": true
           }
         },
         "build": {

docs/shared/recipes/running-tasks/defining-task-pipeline.md

@@ -87,7 +87,23 @@ Or they can be [defined per-project](/reference/project-configuration#dependson)
 {% /tab %}
 {% /tabs %}
 
-## Visualize task dependencies
+## Continuous Task Dependencies
+
+If a task has a dependency that never exits, then the task will never start. To support this scenario, you can mark the dependency as a [continuous task](/reference/project-configuration#continuous). Labeling a task as continuous tells Nx to not wait for the process to exit, and it will be run alongside its dependents.
+
+```json {% fileName="apps/myapp/project.json" %}
+{
+  "targets": {
+    "serve": {
+      "continuous": true
+    }
+  }
+}
+```
+
+The `continuous` option is most useful for running development servers. For example, the `e2e` task depends on a continuous `serve` task that starts the server to be tested againts.
+
+## Visualize Task Dependencies
 
 You can also visualize the actual task graph (alongside the projects) using [Nx graph](/features/explore-graph). This can be useful for debugging purposes.
 

docs/shared/reference/project-configuration.md

@@ -30,7 +30,8 @@ nx show project myproject --web
         "dev": {
           "executor": "nx:run-commands",
           "options": {
-            "command": "vite dev"
+            "command": "vite dev",
+            "continuous": true
           },
           "metadata": {
             "technologies": ["vite"]
@@ -365,10 +366,14 @@ instance, `"dependsOn": ["build"]` of
 the `test` target tells Nx that before it can test `mylib` it needs to make sure that `mylib` is built, which will
 result in `mylib`'s dependencies being built as well.
 
+{% callout type="note" title="Dependencies that do not exit" %}
+If you specify a task in `dependsOn` that never exits, then the dependent task will never start. Label such dependencies as [continuous](#continuous) tasks, which tells Nx to not wait for the process to end before starting the dependent task.
+{% /callout %}
+
 You can also express task dependencies with an object syntax:
 
 {% tabs %}
-{% tab label="Version 16+ (self)" %}
+{% tab label="Dependencies on self" %}
 
 ```json
 {
@@ -386,7 +391,7 @@ You can also express task dependencies with an object syntax:
 ```
 
 {% /tab %}
-{% tab label="Version 16+ (dependencies)" %}
+{% tab label="Dependencies on other projects" %}
 
 ```json
 {
@@ -405,7 +410,7 @@ You can also express task dependencies with an object syntax:
 ```
 
 {% /tab %}
-{% tab label="Version 16+ (specific projects)" %}
+{% tab label="Dependencies on specific projects" %}
 
 ```json
 {
@@ -423,25 +428,6 @@ You can also express task dependencies with an object syntax:
 }
 ```
 
-{% /tab %}
-{% tab label="Version < 16" %}
-
-```json
-{
-  "targets": {
-    "build": {
-      "dependsOn": [
-        {
-          "projects": "dependencies", // "dependencies" or "self"
-          "target": "build", // target name
-          "params": "ignore" // "forward" or "ignore", defaults to "ignore"
-        }
-      ]
-    }
-  }
-}
-```
-
 {% /tab %}
 {% /tabs %}
 
@@ -470,9 +456,6 @@ Starting from v19.5.0, wildcards can be used to define dependencies in the `depe
 
 You can write the shorthand configuration above in the object syntax like this:
 
-{% tabs %}
-{% tab label="Version 16+" %}
-
 ```json
 {
   "targets": {
@@ -486,30 +469,8 @@ You can write the shorthand configuration above in the object syntax like this:
 }
 ```
 
-{% /tab %}
-{% tab label="Version < 16" %}
-
-```json
-{
-  "targets": {
-    "build": {
-      "dependsOn": [{ "projects": "dependencies", "target": "build" }]
-    },
-    "test": {
-      "dependsOn": [{ "projects": "self", "target": "build" }]
-    }
-  }
-}
-```
-
-{% /tab %}
-{% /tabs %}
-
 With the expanded syntax, you also have a third option available to configure how to handle the params passed to the target. You can either forward them or you can ignore them (default).
 
-{% tabs %}
-{% tab label="Version 16+" %}
-
 ```json
 {
   "targets": {
@@ -533,40 +494,8 @@ With the expanded syntax, you also have a third option available to configure ho
 }
 ```
 
-{% /tab %}
-{% tab label="Version < 16" %}
-
-```json
-{
-  "targets": {
-    "build": {
-      // forward params passed to this target to the dependency targets
-      "dependsOn": [
-        { "projects": "dependencies", "target": "build", "params": "forward" }
-      ]
-    },
-    "test": {
-      // ignore params passed to this target, won't be forwarded to the dependency targets
-      "dependsOn": [
-        { "projects": "dependencies", "target": "build", "params": "ignore" }
-      ]
-    },
-    "lint": {
-      // ignore params passed to this target, won't be forwarded to the dependency targets
-      "dependsOn": [{ "projects": "dependencies", "target": "build" }]
-    }
-  }
-}
-```
-
-{% /tab %}
-{% /tabs %}
-
 This also works when defining a relation for the target of the project itself using `"projects": "self"`:
 
-{% tabs %}
-{% tab label="Version 16+" %}
-
 ```json
 {
   "targets": {
@@ -578,30 +507,8 @@ This also works when defining a relation for the target of the project itself us
 }
 ```
 
-{% /tab %}
-{% tab label="Version < 16" %}
-
-```json
-{
-  "targets": {
-    "build": {
-      // forward params passed to this target to the project target
-      "dependsOn": [
-        { "projects": "self", "target": "pre-build", "params": "forward" }
-      ]
-    }
-  }
-}
-```
-
-{% /tab %}
-{% /tabs %}
-
 Additionally, when using the expanded object syntax, you can specify individual projects in version 16 or greater.
 
-{% tabs %}
-{% tab label="Version 16+" %}
-
 ```json
 {
   "targets": {
@@ -615,12 +522,42 @@ Additionally, when using the expanded object syntax, you can specify individual
 }
 ```
 
-{% /tab %}
-{% /tabs %}
-
 This configuration is usually not needed. Nx comes with reasonable defaults (imported in `nx.json`) which implement the
 configuration above.
 
+### Continuous
+
+In Nx 21+, tasks that never exit (sometimes called long-running processes) can be configured with `"continuous": true` to prevent their dependent tasks from waiting for task completion. For example, the `e2e` task depends on a continuous `serve` task to ensure that the development server is running.
+
+In this example, application's configuration labels the `serve` task as continuous.
+
+```json {% fileName="apps/myapp/project.json" %}
+{
+  "targets": {
+    "serve": {
+      "continuous": true
+    }
+  }
+}
+```
+
+And the E2E project's `e2e` task has a dependency on the `serve` task, which ensures that the server is running when we run the `e2e` task.
+
+```json {% fileName="apps/myapp-e2e/project.json" %}
+{
+  "targets": {
+    "e2e": {
+      "dependsOn": [
+        {
+          "projects": "myapp",
+          "target": "serve"
+        }
+      ]
+    }
+  }
+}
+```
+
 ### Sync Generators
 
 In the same way that `dependsOn` tells Nx to run another task before running this task, the `syncGenerator` property tells Nx to run a generator to ensure that your files are in the correct state before this task is run. [Sync generators](/concepts/sync-generators) are especially useful for keeping configuration files up to date with the project graph. Sync generators are available in Nx 19.8+.