We can do better...

## What makes a dependency { #what-makes-a-dependency }

Up to now you have seen dependencies declared as functions.

But that's not the only way to declare dependencies (although it would probably be the more common).

The key factor is that a dependency should be a "callable".

A "**callable**" in Python is anything that Python can "call" like a function.

    </dependency>
    <dependency>
      <groupId>org.jline</groupId>
      <artifactId>jline-terminal-jni</artifactId>
    </dependency>
    <dependency>
      <groupId>org.jline</groupId>
      <artifactId>jline-terminal-ffm</artifactId>
    </dependency>

    <!-- (legacy) DI annotations -->
    <dependency>
      <groupId>javax.inject</groupId>
      <artifactId>javax.inject</artifactId>
    </dependency>

import org.apache.maven.api.annotations.Nonnull;

/**
 * Indicates when the dependency will be used.
 * For example, it may be at compile time only, at runtime, or at test time.
 * For a given dependency, the scope is directly derived from the
 * {@link org.apache.maven.api.model.Dependency#getScope()} and will be used when using {@link PathScope}
 * and the {@link org.apache.maven.api.services.DependencyResolver}.

name: 'Dependency Review'
on: [pull_request]

permissions:
  contents: read

jobs:
  dependency-review:
    runs-on: ubuntu-latest
    steps:
      - name: 'Checkout Repository'
        uses: actions/checkout@v4
      - name: 'Dependency Review'

///

## Dependencies errors and return values { #dependencies-errors-and-return-values }

You can use the same dependency *functions* you use normally.

### Dependency requirements { #dependency-requirements }

They can declare request requirements (like headers) or other sub-dependencies:

{* ../../docs_src/dependencies/tutorial006_an_py39.py hl[8,13] *}

    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-api-settings</artifactId>
    </dependency>
    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-api-toolchain</artifactId>
    </dependency>
    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-api-plugin</artifactId>
    </dependency>
    <dependency>

    }

    private static String formatLocationInPom(Dependency dependency) {
        return "Dependency: " + ArtifactUtils.versionlessKey(dependency.getGroupId(), dependency.getArtifactId());
    }

    public Dependency getDependency() {
        return dependency;
    }

    public String getProjectId() {
        return projectId;
    }

    public File getPomFile() {
        return pomFile;
    }

This is quite simple (not very useful), but will help us focus on how the sub-dependencies work.

## Second dependency, "dependable" and "dependant" { #second-dependency-dependable-and-dependant }

Then you can create another dependency function (a "dependable") that at the same time declares a dependency of its own (so it is a "dependant" too):

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[13] *}

Let's focus on the parameters declared:

			<version>1.7.36</version>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-reload4j</artifactId>
			<version>1.7.36</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.bouncycastle</groupId>
			<artifactId>bcprov-jdk18on</artifactId>
			<version>1.80</version>
		</dependency>
		<dependency>
			<groupId>org.junit.jupiter</groupId>

     *
     * @param dependency path to the dependency for which to get the module name
     * @return module name of the dependency at the given path, or empty if the dependency is not modular
     * @throws IOException if the module information of the specified dependency cannot be read
     */
    Optional<ModuleDescriptor> getModuleDescriptor(@Nonnull Path dependency) throws IOException;

    /**