Errors

Package exceptions implement ExceptionInterface. Catch a precise exception when the application can recover, or catch the interface at a request, job, or command boundary.

Failure Cause Recovery
InvalidEntryException Empty specifier, or a prefix specifier whose non-null address does not end in / Supply a non-empty key and keep both sides of prefix mappings slash-terminated
SpecifierNotFoundException No scoped, top-level, or URL-like match exists Check spelling and add the intended mapping
ResolutionFailedException An exact mapping deliberately contains null Remove or replace the block only when the application should permit that dependency
JsonException fromJson() receives invalid JSON, or output contains bytes JSON cannot encode Correct the input and preserve valid UTF-8 data
RuntimeException fromFile() cannot find or read its path Check the application-authorized path and permissions

SpecifierNotFoundException extends ResolutionFailedException, so catching the parent handles both missing and blocked imports. When scoped resolution is unexpected, verify the referencing URL: the longest matching scope takes priority, then resolution falls back through shorter scopes and top-level imports.

The package does not verify that a resolved address exists or that a browser can fetch it. For browser failures, inspect the rendered map, document base URL, network response, and content security policy in the consuming application.