Ban External Imports
This constraint is only available for projects using ESLint.
You may want to constrain what external packages a project may import. For example, you may want to prevent backend projects from importing packages related to your frontend framework. You can ban these imports using bannedExternalImports property in your dependency constraints configuration.
A common example of this is for backend projects that use NestJS and frontend projects that use Angular. Both frameworks contain a class named Injectable. It's very easy for a developer to import the wrong one by mistake, especially when using auto-import in an IDE. To prevent this, add tags to define the type of project to distinguish between backend and frontend projects. Each tag should define its own list of banned external imports.
{
// ... more ESLint config here
// nx-enforce-module-boundaries should already exist at the top-level of your config
"nx-enforce-module-boundaries": [
"error",
{
"allow": [],
// update depConstraints based on your tags
"depConstraints": [
// projects tagged with "frontend" can't import from "@nestjs/common"
{
"sourceTag": "frontend",
"bannedExternalImports": ["@nestjs/common"]
},
// projects tagged with "backend" can't import from "@angular/core"
{
"sourceTag": "backend",
"bannedExternalImports": ["@angular/core"]
}
]
}
]
// ... more ESLint config here
}
Another common example is ensuring that util libraries stay framework-free by banning imports from these frameworks. You can use wildcard * to match multiple projects e.g. react* would match react, but also react-dom, react-native etc. You can also have multiple wildcards e.g. *react* would match any package with word react in it's name. A workspace using React would have a configuration like this.
{
// ... more ESLint config here
// nx-enforce-module-boundaries should already exist at the top-level of your config
"nx-enforce-module-boundaries": [
"error",
{
"allow": [],
// update depConstraints based on your tags
"depConstraints": [
// projects tagged with "type:util" can't import from "react" or related projects
{
"sourceTag": "type:util",
"bannedExternalImports": ["*react*"]
}
]
}
]
// ... more ESLint config here
}