Fix unresolved optional dependencies causing other dependencies to be skipped.

Add unit tests for dependency resolution error messages.

Implement a recursion based dependency resolution algorithm. ...

Although this is rather expensive in terms of memory allocation and stack usage, it does a much better job at reducing the number of combinations that have to be tested.

Rename ConfigEntry to PackageConfigs and avoid GC allocation.

adjust code style to request

Fix #1037

Remove compatibility code for DMD frontends < 2.067.x.

Defer error message generation to the end of the dependency resolution process.

Put a hard limit in the number of dependency resolution iterations. ...

This avoids the process getting stuck in the resolution phase "indefinitely", so that for example CI runs don't get stuck anymore. It also communicates the problem and potential resolutions more clearly. If the DUB_NO_RESOLVE_LIMIT environment variable is set, the resolution process will run without this limit.

Small optimizations in DependencyResolver.

Fix diagnostic output for dependency resolution failures.

Fix recursive graph traversal. Fixes #923.

Don't ever reset the any_config flag to false. Fixes #896. ...

Avoids a bad error message indicating a missing *package* when it really is only missing a suitable *version*. Occurs for dependencies that have multiple incoming references, with an unsatisfyable version reference coming form the root package.

Fix second failing case of #803.

Fix naming of rootPackage() helper.

Avoid repeated addition of the same dependency in DependencyResolver.

Fix dependency resolution for unsatisfyable optional dependencies. ...

If another (unchosen) dependency in the graph had a required dependency to the unsatisfyable version, the resolution process failed, even if not choosing the dependency would have been valid.

Add additional unit test for optional dependencies.

Improve error message for unsatisfiable root dependencies.

Filter out invalid dependencies before starting the resolution process. ...

Package versions for which it is not possible to get an actual package description (e.g. due to non-existent paths or semantic errors in the package description) are now excluded from the dependency resolution process. Before this, they could erroneously be picked, resulting in an malformed dependency tree.

Fix purging of optional dependencies when sub packages are involved.

Extend DependencyResolver to properly handle optional dependencies.

Mention version for invalid root package dependencies.

Fix warnings on DMD master. See #541.

Fix detection of unknown root dependencies and the resulting error message. Fixes #418.

Eliminate dependency versions that are known to not match the root package. See #405. ...

This change eliminates all dependency versions that are known to violate the dependency specification of the root package or of uniquely defined dependencies thereof. This can greatly reduce the search space for valid combinations later on in the algorithm.

Add missing recursion during dependency resolution. See #405.

Add an early out for invalid child configurations in the dependency resolver. Fixes #405. ...

Previous behavior could cause exponential run time.

Fix using an invalid configuration in DependencyResolver when validating dependencies. ...

This was caused by the fix for #359.

Fix DependencyResolver's unit test.