Dependency Selector Syntax & Querying

Description

The npm query commmand exposes a new dependency selector syntax (informed by & respecting many aspects of the CSS Selectors 4 Spec) which:

• Standardizes the shape of, & querying of, dependency graphs with a robust object model, metadata & selector syntax
• Leverages existing, known language syntax & operators from CSS to make disparate package information broadly accessible
• Unlocks the ability to answer complex, multi-faceted questions about dependencies, their relationships & associative metadata
• Consolidates redundant logic of similar query commands in npm (ex. npm fund, npm ls, npm outdated, npm audit ...)

Dependency Selector Syntax v1.0.0

Overview:

• there is no "type" or "tag" selectors (ex. div, h1, a) as a dependency/target is the only type of Node that can be queried
• the term "dependencies" is in reference to any Node found in a tree returned by Arborist

Combinators

• > direct descendant/child
• any descendant/child
• ~ sibling

Selectors

• * universal selector
• #<name> dependency selector (equivalent to [name="..."])
• #<name>@<version> (equivalent to [name=<name>]:semver(<version>))
• , selector list delimiter
• . dependency type selector
• : pseudo selector

Dependency Type Selectors

• .prod dependency found in the dependencies section of package.json, or is a child of said dependency
• .dev dependency found in the devDependencies section of package.json, or is a child of said dependency
• .optional dependency found in the optionalDependencies section of package.json, or has "optional": true set in its entry in the peerDependenciesMeta section of package.json, or a child of said dependency
• .peer dependency found in the peerDependencies section of package.json
• .workspace dependency found in the workspaces section of package.json
• .bundled dependency found in the bundleDependencies section of package.json, or is a child of said dependency

Pseudo Selectors

• :not(<selector>)
• :has(<selector>)
• :is(<selector list>)
• :root matches the root node/dependency
• :scope matches node/dependency it was queried against
• :empty when a dependency has no dependencies
• :private when a dependency is private
• :link when a dependency is linked (for instance, workspaces or packages manually linked
• :deduped when a dependency has been deduped (note that this does not always mean the dependency has been hoisted to the root of node_modules)
• :overridden when a dependency has been overridden
• :extraneous when a dependency exists but is not defined as a dependency of any node
• :invalid when a dependency version is out of its ancestors specified range
• :missing when a dependency is not found on disk
• :semver(<spec>) matching a valid node-semver spec
• :path(<path>) glob matching based on dependencies path relative to the project
• :type(<type>) based on currently recognized types

Attribute Selectors

The attribute selector evaluates the key/value pairs in package.json if they are Strings.

• [] attribute selector (ie. existence of attribute)
• [attribute=value] attribute value is equivalant...
• [attribute~=value] attribute value contains word...
• [attribute*=value] attribute value contains string...
• [attribute|=value] attribute value is equal to or starts with...
• [attribute^=value] attribute value starts with...
• [attribute$=value] attribute value ends with...

Array & Object Attribute Selectors

The generic :attr() pseudo selector standardizes a pattern which can be used for attribute selection of Objects, Arrays or Arrays of Objects accessible via Arborist's Node.package metadata. This allows for iterative attribute selection beyond top-level String evaluation. The last argument passed to :attr() must be an attribute selector or a nested :attr(). See examples below:

Objects

/* return dependencies that have a `scripts.test` containing `"tap"` */
*:attr(scripts, [test~=tap])

Nested Objects

Nested objects are expressed as sequential arguments to :attr().

/* return dependencies that have a testling config for opera browsers */
*:attr(testling, browsers, [~=opera])

Arrays

Arrays specifically uses a special/reserved . character in place of a typical attribute name. Arrays also support exact value matching when a String is passed to the selector.

Example of an Array Attribute Selection:

/* removes the distinction between properties & arrays */
/* ie. we'd have to check the property & iterate to match selection */
*:attr([keywords^=react])
*:attr(contributors, :attr([name~=Jordan]))

Example of an Array matching directly to a value:

/* return dependencies that have the exact keyword "react" */
/* this is equivalent to `*:keywords([value="react"])` */
*:attr([keywords=react])

Example of an Array of Objects:

/* returns */
*:attr(contributors, [email=ruyadorno@github.com])

Groups

Dependency groups are defined by the package relationships to their ancestors (ie. the dependency types that are defined in package.json). This approach is user-centric as the ecosystem has been taught to think about dependencies in these groups first-and-foremost. Dependencies are allowed to be included in multiple groups (ex. a prod dependency may also be a dev dependency (in that it's also required by another dev dependency) & may also be bundled - a selector for that type of dependency would look like: *.prod.dev.bundled).

• .prod
• .dev
• .optional
• .peer
• .bundled
• .workspace

Please note that currently workspace deps are always prod dependencies. Additionally the .root dependency is also considered a prod dependency.

Programmatic Usage

• Arborist's Node Class has a .querySelectorAll() method
  • this method will return a filtered, flattened dependency Arborist Node list based on a valid query selector

const Arborist = require('@npmcli/arborist')
const arb = new Arborist({})

// root-level
arb.loadActual().then(async (tree) => {
  // query all production dependencies
  const results = await tree.querySelectorAll('.prod')
  console.log(results)
})

// iterative
arb.loadActual().then(async (tree) => {
  // query for the deduped version of react
  const results = await tree.querySelectorAll('#react:not(:deduped)')
  // query the deduped react for git deps
  const deps = await results[0].querySelectorAll(':type(git)')
  console.log(deps)
})

See Also

• npm query
• @npmcli/arborist