@yanice/import-boundaries

Purpose

This package serves as a plugin for yanice. Without yanice, the package is of little value.

Installation

Install e.g. via npm as follows:

npm install --save-dev @yanice/import-boundaries

Usage

The plugin can be invoked via yanice:

yanice plugin:import-boundaries <scope> --assert

scope must be defined in the yanice.json under dependencyScopes. See further below for more examples and explanations.

Configuration

Configuration of the plugin is done in the yanice.json, see here for an example:

{
    "import-boundaries": {
        "importResolvers": {
            "**/*.some-extension": ["./some-custom-resolver.js"],
            "**/*.{js,ts}": ["es6-declarative-import-resolver"]
        },
        "postResolve": ["./post-resolve.js"],
        "assertions": ["only-direct-imports", "use-all-declared-dependencies"],
        "customAssertions": ["./some-custom-assertion.js"],
        "assertionOptions": {
            "skippedImports": {
                "amount": 0,
                "mode": "exact"
            },
            "ignoredProjects": ["ALL-FILES"]
        }
    }
}

importResolvers

A map that maps glob-expressions to an array of import-resolvers. An import-resolver accepts a file and its filepath and creates an "import-map". See here for an example how a custom import resolver can be written: dummy-resolver.ts. Note that we ultimately need to provide a JS-file, meaning, the aforementioned code would first need to be transpiled.

Officially available resolvers:

• es6-declarative-import-resolver: Resolves all import ... from ...-statements.

Currently missing (will follow later):

• common-js: Use of require is currently ignored
• dynamic imports: import(..) and await import(..) are currently ignored as well

postResolve

The plugin will create an import-map for all files that matched. In case anything is amiss or the plugin was not able to resolve certain imports, in this step we can do one final mapping. One possible use-case is to resolve typescript-path-mappings here.

assertions

Array of officially provided assertions. Currently supported:

• only-direct-imports: Forces that only imports to projects which are defined as a direct dependency in the given scope are allowed. E.g.: A file in project-A imports a file from project-B - this is only allowed if "project-A": ["project-B", ...] is declared in the yanice.json.
• only-transitive-dependencies: Similar to only-direct-imports, but allowing for transitive dependencies: When we declare A to depend on B which depends on C, A is also allowed to import from C.
• use-all-declared-dependencies: Similar to only-direct-imports, but the other way around: Any declared dependency must be used. I.e., if project-A depends on project-B as per yanice.json, then project-A must indeed import project-B.
• max-skipped-imports: See also how to ignore imports below. The rule allows to check/enforce only a certain amount of skipped imports.
• access-via-entrypoints: It is sometimes desirable to access a project from other projects only via defined entrypoints, such as e.g. an index.ts, public_api.ts or some such, and disallow "deep" imports to arbitrary files. This rule helps with that. Define one or multiple entry-points via the entrypoints-property for each project. This rule will then ensure that every import from another project accesses the project via a defined entrypoint.

customAssertions

Array of custom assertion scripts. See here on how to provide a script; the original untranspiled assertion-source-code can be found here: link to dummy-assertion.

assertionOptions

• ignoredProjects: The rules related to boundary-assertions will ignore any listed project. This is especially helpful for "metaprojects" like all-files, all-typescript-files etc.
• skippedImports: Only relevant when using max-skipped-imports. Define the amount of allowed skipped imports. The mode-property defines how the number is interpreted.
• accessViaEntryPoints: Only relevant when using access-via-entrypoints. The allowWithinSameProject-flag controls whether entrypoint-access from within the same project is allowed. E.g., if the index.js is an entrypoint of project-A, whether any other file within project-A is allowed to import from the index.js. By default, this is not the case, as this often leads to undesired import-circles.

Ignoring a particular import

No rule without an exception. When an import statement is preceded with an ignore-comment // @yanice:import-boundaries ignore-next-line, the given import-statement is not considered for assertions:

// @yanice:import-boundaries ignore-next-line
import { something } from './some/illegal/file';

Commands

The plugin can be invoked with the following parameters:

Main Options:

• --assert: The default mode; will be used when no other main option is present. Runs all configured assertions.
• --print-file-imports: Will print file-import-maps as soon as they are available, without any yanice-project-related information.
• --print-assertion-data: Will print all data that is being generated to run assertions. The aforementioned file-import-map, which file belongs to which project, and which project imports which project.
• --generate: Will print the project-dependencies based on the imports in the format that the yanice.json uses

Additional Options:

• --skip-post-resolvers: Skips the post-resolvers.
• --perf-log (or --performance-logging): Adds some extra logs to show how much time was spent on which operation.

Examples

A good starting point is to print the project-map generated by the plugin. Note that a dependency-scope (here: build) must be provided and configured in the yanice.json.

yanice plugin:import-boundaries build --print-project-imports

Note that the output might be fairly big; as it is in *.json-format, piping it into a file might be convenient:

yanice plugin:import-boundaries build --print-project-imports > project-import-map.json

Run the plugin for the build-dependency-scope, generating the project-dependencies as per imports in the yanice.json-format:

yanice plugin:import-boundaries build --generate --skip-post-resolvers

Print the file-import-maps without any yanice-project-related information, also skipping any post-resolver:

plugin:import-boundaries a-depends-on-b --print-project-imports --skip-post-resolvers