Include directive processing in the browser

This document describes how the include directive is processed in the browser environment (xmlhttprequest IO module). This handling has slightly different rules than when a file-based document. The rules are listed in the order in which they are applied.

In these definitions, there are several commonly occurring terms that pertain to the include directive:

  • target - the target of the include directive as specified in the document

  • include path - the resolved path of the include; usually an absolute path or URL

  • relative path - the path of the include relative to the root document unless the include path is absolute

  • base dir - the base directory defined on the processor; usually matches the directory of the root document

  • parent dir - the directory of the file containing a nested include; nested includes are resolved relative to the file in which they occur

Since the browser doesn’t know the environment the document was intended for, the path resolver is initialized to consider paths with both forward and backslashes.

Top-level include

  • If the target starts with file://, the target is used as both the include path and the relative path. In this case, the base dir value has no impact.

  • If the target is an absolute URL (i.e., starts with http:// or https:// scheme), the target must either descend from the base dir or the allow-uri-read attribute must be set on the document. If either test succeeds, the target is used as both the include path and the relative path. If both these tests fail, the include is replaced with a link.

  • If the target is an absolute path (i.e., starts with a posix root, a Windows drive letter, or a UNC path), the file:// scheme (or / if the path starts with a Windows drive letter) is prepended to the target and the result is used as both the include path and the relative path. In this case, the base dir value has no impact.

  • If the target is relative and the base dir equals ., the target is used as both the include path and the relative path. The include path will be resolved relative to the window.location.href (per the behavior of XMLHttpRequest).

  • If the target is relative and the base dir begins with file://, the base dir is prepended to the target to create the include path. The target is used as the relative path.

  • If the target is relative and the base dir is relative, the base dir is prepended to the target to create the include path. The include path will be resolved relative to the window.location.href (per the behavior of XMLHttpRequest). The target is used as the relative path.

  • If the target is relative and the base dir is an absolute URL (i.e., starts with http:// or https:// scheme), the base dir is prepended to the target and used as the include path. The target is used as the relative path.

Nested include

  • If the target starts with file://, the target is used as both the include path and the relative path. In this case, the base dir value has no impact.

  • If the target is a URL (starts with http:// or https:// scheme), the target must either descend from the base dir or the allow-uri-read attribute must be set on the document. If both these tests fail, the include is replaced with a link. If either test succeeds, the target is used as both the include path and the relative path.

  • If the target is an absolute path (i.e., starts with a posix root, a Windows drive letter, or a UNC path), the file:// scheme (or / when the path starts with a Windows drive letter) is prepended to the target and the result is used as both the include path and the relative path. In this case, the base dir value has no impact.

  • If the target is relative and the parent dir equals ., the target is used as both the include path and the relative path. The include path will be resolved relative to window.location.href (per the behavior of XMLHttpRequest).

  • If the target is relative and the parent dir begins with file://, the parent dir is prepended to the target to create the include path. If the base dir equals ., or the include path does not descend from the base dir, the include path is used as the relative path. If the include path descends from the base dir, the relative path is the path difference.

  • If the target is relative and the parent dir is relative, the parent dir is prepended to the target to create the include path. The include path will be resolved relative to the window.location.href (per the behavior of XMLHttpRequest). If the base dir equals ., or the include path does not descend from the base dir, the include path is used as the relative path. If the include path descends from the base dir, the relative path is the path difference.

  • If the target is relative and the parent dir is an absolute URL (i.e., starts with http:// or https:// scheme), the parent dir must descend from the base dir or the allow-uri-read attribute must be set on the document. If either test succeeds, the parent dir is prepended to the target and used as the include path. If the parent dir descends from the base dir, the relative path is the path difference. Otherwise, the relative path is the target. If both these tests fail, the include is replaced with a link.