Transparently add the \\?\ prefix to Win32 calls for extended length path handling #1257
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Tests/FoundationEssentialsTests/FileManager/FileManagerTests.swift
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A few minor comments on the unit test, but overall this looks good - thanks for putting this together! Added @jrflat as a reviewer as well just for another perspective from the URL side of things in case there's any considerations/impact there.
…path handling On Windows, there is a built-in maximum path limitation of 260 characters under most conditions. This can be extended to 32767 characters under either of the following two conditions: - Adding the longPathAware attribute to the executable's manifest AND enabling the LongPathsEnabled system-wide registry key or group policy. - Ensuring fully qualified paths passed to Win32 APIs are prefixed with \?\ Unfortunately, the former is not realistic for the Swift ecosystem, since it requires developers to have awareness of this specific Windows limitation, AND set longPathAware in their apps' manifest AND expect end users of those apps to change their system configuration. Instead, this patch transparently prefixes all eligible paths in calls to Win32 APIs with the \?\ prefix to allow them to work with paths longer than 260 characters without requiring the caller of Foundation to manually prefix the paths. See https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation for more info.
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Thanks @jmschonfeld and @compnerd; I've addressed all your feedback so far. |
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@jakepetroules any chance that we might be able to pull this into 6.2 as well? 😄 |
Happy to -- @jmschonfeld / @parkera, is your team doing regular merges from main to 6.2 or should I manually bring it over? |
| // 1. Normalize the path first. | ||
| // Contrary to the documentation, this works on long paths independently | ||
| // of the registry or process setting to enable long paths (but it will also |
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Ah, it states the truth on this page instead of the docs for GetFullPathName itself:
You can pass paths of more than
MAX_PATHcharacters to GetFullPathName without\\?\. It supports arbitrary length paths up to the maximum string size that Windows can handle.
@parkera / @itingliu can confirm but I believe our plan is to have periodic merges from |
…path handling This simply updates the implementation of withNTPathRepresentation with what's about to be merged into Foundation via swiftlang/swift-foundation#1257
On Windows, there is a built-in maximum path limitation of 260 characters under most conditions. This can be extended to 32767 characters under either of the following two conditions:
Unfortunately, the former is not realistic for the Swift ecosystem, since it requires developers to have awareness of this specific Windows limitation, AND set longPathAware in their apps' manifest AND expect end users of those apps to change their system configuration.
Instead, this patch transparently prefixes all eligible paths in calls to Win32 APIs with the ?\ prefix to allow them to work with paths longer than 260 characters without requiring the caller of Foundation to manually prefix the paths.
See https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation for more info.