import org.apache.maven.internal.impl.DefaultLookup;
import org.apache.maven.internal.impl.DefaultSession;
import org.apache.maven.internal.impl.DefaultSessionFactory;
import org.apache.maven.model.building.ModelBuildingException;
import org.apache.maven.model.building.ModelProblem;
import org.codehaus.plexus.PlexusContainer;
import org.codehaus.plexus.testing.PlexusTest;
import org.eclipse.aether.DefaultRepositoryCache;

import org.apache.maven.internal.impl.resolver.DefaultModelRepositoryHolder;
import org.apache.maven.model.building.ArtifactModelSource;
import org.apache.maven.model.building.DefaultModelProblem;
import org.apache.maven.model.building.FileModelSource;
import org.apache.maven.model.building.ModelSource2;
import org.apache.maven.model.building.ModelSource3;
import org.apache.maven.model.resolution.UnresolvableModelException;

 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.building;

/**
 * Describes a problem that was encountered during settings building. A problem can either be an exception that was
 * thrown or a simple string message. In addition, a problem carries a hint about its source, e.g. the settings file
 * that exhibits the problem.

So, it was a complete additional system.

It is not very popular or used nowadays.

## OpenAPI

OpenAPI (previously known as Swagger) is the open specification for building APIs (now part of the Linux Foundation).

**FastAPI** is based on **OpenAPI**.

That's what makes it possible to have multiple automatic interactive documentation interfaces, code generation, etc.

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.building;

import java.util.ArrayList;
import java.util.List;

/**
 * Collects problems that are encountered during settings building.
 *
 */
class DefaultProblemCollector implements ProblemCollector {

    private final List<Problem> problems;

    private String source;

     * Gets the problems that were encountered during the settings building. Note that only problems of severity
     * {@link BuilderProblem.Severity#WARNING} and below are reported here. Problems with a higher severity level cause
     * the settings builder to fail with a {@link ToolchainsBuilderException}.
     *
     * @return the problems that were encountered during the settings building, can be empty but never {@code null}
     */
    @Nonnull

     *
     * @param model The model whose duplicate elements should be merged, must not be {@code null}.
     * @param request The model building request that holds further settings, must not be {@code null}.
     * @param problems The container used to collect problems that were encountered, must not be {@code null}.
     */

    /**
     * Builds the effective toolchains for the specified toolchains files.
     *
     * @param request the toolchains building request that holds the parameters, must not be {@code null}
     * @return the result of the toolchains building, never {@code null}
     * @throws ToolchainsBuilderException if the effective toolchains could not be built
     */

/**
 * Replaces expressions of the form <code>${token}</code> with their effective values. Effective values are basically
 * calculated from the elements of the model itself and the execution properties from the building request.
 *
 */
public interface ModelInterpolator {

    /**
     * Interpolates expressions in the specified model. Note that implementations are free to either interpolate the

     * @return The unresolved dependencies, never {@code null}.
     */
    List<Dependency> getUnresolvedDependencies();

    /**
     * Gets the errors that occurred while building the dependency graph.
     *
     * @return The errors that occurred while building the dependency graph, never {@code null}.
     */
    List<Exception> getCollectionErrors();

    /**