Project Inference
ExperimentalThis API is experimental and might change.
Project inference describes the ability of Nx to discover and work with projects based on source code and configuration files in your repo. Out of the box, Nx identifies projects based on the presence of package.json
and project.json
files. It also identifies targets in the package.json
scripts and the project.json
target
s.
Project inference plugins allow you to extend this functionality of Nx to other languages and file structures.
Adding Plugins to Workspace
You can register a plugin by adding it to the plugins array in nx.json
:
{
...,
"plugins": [
"awesome-plugin"
]
}
Project File Patterns
Project file patterns are used in two scenarios:
- Inferring projects
- Determining which files should be passed into
registerProjectTargets
.
Let's use the below plugin and workspace layout as an example:
export const projectFilePatterns = ['project.json', 'my-other-project-file'];
export function registerProjectTargets(projectFilePath) {
console.log(projectFilePath);
}
workspace layout
my-workspace/
├─ node_modules/
├─ libs/
│ ├─ my-project/
│ │ ├─ my-other-project-file
│ ├─ nx-project/
│ │ ├─ my-other-project-file
│ │ ├─ project.json
├─ nx.json
└─ package.json
During initialization, we would expect to see "libs/my-project/my-other-project-file", "libs/nx-project/my-other-project-file", "libs/nx-project/project.json" all logged out to the console. Nx was able to infer my-project
from the layout.
Implementing a Project Target Configurator
A project target configurator is a function that takes a path to a project file, and returns the targets inferred from that file.
Plugins should export a function named registerProjectTargets
that infers the targets from each matching project file. This function receives the path to the project file as its sole parameter.
The registerProjectTargets
function should return a Record<string, TargetConfiguration>
, which describes the targets inferred for that specific project file.
import { TargetConfiguration } from '@nrwl/devkit';
export const projectFilePatterns = ['project.json', 'my-other-project-file'];
export function registerProjectTargets(
projectFilePath: string
): Record<string, TargetConfiguration> {
return {
build: {
/**
* This object should look exactly like a target
* configured inside `project.json`
*/
},
};
}
Multiple Matches
It is possible that the registerProjectTargets function may be called multiple times for one project. This could occur in a few cases, one of which is demonstrated above.
- One plugin may list multiple file patterns, and a project may match more than one of them.
- Multiple plugins may list similar patterns, and pick up the project separately.
In the first case, the plugin that you are writing will be called into multiple times. If you return the same target (e.g. build
) on each call, whichever is ran last would be the target that Nx calls into.
The order that the function would be called is NOT guaranteed, so you should try to avoid this when possible. If specifying multiple patterns, they should either be mutually exclusive (e.g. one match per project) or the plugin should conditionally add targets based on the file passed in.
In the second case, different plugins may attempt to register the same target on a project. If this occurs, whichever target was registered by the plugin listed latest in nx.json
would be the one called into by Nx. As an example, assume plugin-a
, plugin-b
, and plugin-c
all match a file and register build
as a target. If nx.json
included "plugins": ["plugin-a", "plugin-b", "plugin-c"]
, running nx build my-project
would run the target as defined by "plugin-c"
.
Alternatively, if nx.json
included "plugins": ["plugin-c", "plugin-b", "plugin-a"]
, running nx build my-project
would run the target as defined by "plugin-a"
.
Development Tips
There is a cache that Nx uses to avoid recalculating the project graph as much as possible, but it may need to be skipped during plugin development. You can set the following environment variable to disable the project graph cache: NX_CACHE_PROJECT_GRAPH=false
.
It might also be a good idea to ensure that the dep graph is not running on the nx daemon by setting NX_DAEMON=false
, as this will ensure you will be able to see any console.log
statements you add as you're developing. You can also leave the daemon active, but console.log
statements would only appear in its log file.