Code change:
Refs: I do not understand this condition: How does that make sure a method exists? The only check for this that is valid currently is , the is just a detail of the file system and not a capability.
This looks like an actual typo to me or missing code review, not sure the consequences, as it could lead to errors when wrongly asserting, so maybe moving to August for investigation.
TLDR I misunderstood how the declared capabilities relate to the actual declared methods and the meaning of . For context, this change came in through and the intention of this change was to support the scenario where an has declared but not : since is optional in the interface and the capability requires both and to be implemented: I made this change because when implementing a with but not , this would result in throwing here: I see how it's possible that a which has check does not have a method implemented. Additionally I see that we have other examples of how to handle the requirement of a readonly filesystem which implements both and , e.g.: I am reverting Apologies for the incorrect code change and thank you for pointing this out.

Related discussion:
text: import { consumeStream, isReadableBufferedStream, isReadableStream, listenStream, newWriteableStream, peekReadable, peekStream, transform } from 'vs/base/common/stream'; import { URI } from 'vs/base/common/uri'; import { localize } from 'vs/nls'; <del> import { ensureFileSystemProviderError, etag, ETAG_DISABLED, FileChangesEvent, IFileDeleteOptions, FileOperation, FileOperationError, FileOperationEvent, FileOperationResult, FilePermission, FileSystemProviderCapabilities, FileSystemProviderErrorCode, FileType, hasFileAtomicReadCapability, hasFileFolderCopyCapability, hasFileReadStreamCapability, hasOpenReadWriteCloseCapability, hasReadWriteCapability, ICreateFileOptions, IFileContent, IFileService, IFileStat, IFileStatWithMetadata, IFileStreamContent, IFileSystemProvider, IFileSystemProviderActivationEvent, IFileSystemProviderCapabilitiesChangeEvent, IFileSystemProviderRegistrationEvent, IFileSystemProviderWithFileAtomicReadCapability, IFileSystemProviderWithFileReadStreamCapability, IFileSystemProviderWithFileReadWriteCapability, IFileSystemProviderWithOpenReadWriteCloseCapability, IReadFileOptions, IReadFileStreamOptions, IResolveFileOptions, IFileStatResult, IFileStatResultWithMetadata, IResolveMetadataFileOptions, IStat, IFileStatWithPartialMetadata, IWatchOptions, IWriteFileOptions, NotModifiedSinceFileOperationError, toFileOperationResult, toFileSystemProviderErrorCode, hasFileCloneCapability, hasFileReadCapability, IFileSystemProviderWithFileReadCapability } from 'vs/platform/files/common/files'; </del> <ins> import { ensureFileSystemProviderError, etag, ETAG_DISABLED, FileChangesEvent, IFileDeleteOptions, FileOperation, FileOperationError, FileOperationEvent, FileOperationResult, FilePermission, FileSystemProviderCapabilities, FileSystemProviderErrorCode, FileType, hasFileAtomicReadCapability, hasFileFolderCopyCapability, hasFileReadStreamCapability, hasOpenReadWriteCloseCapability, hasReadWriteCapability, ICreateFileOptions, IFileContent, IFileService, IFileStat, IFileStatWithMetadata, IFileStreamContent, IFileSystemProvider, IFileSystemProviderActivationEvent, IFileSystemProviderCapabilitiesChangeEvent, IFileSystemProviderRegistrationEvent, IFileSystemProviderWithFileAtomicReadCapability, IFileSystemProviderWithFileReadStreamCapability, IFileSystemProviderWithFileReadWriteCapability, IFileSystemProviderWithOpenReadWriteCloseCapability, IReadFileOptions, IReadFileStreamOptions, IResolveFileOptions, IFileStatResult, IFileStatResultWithMetadata, IResolveMetadataFileOptions, IStat, IFileStatWithPartialMetadata, IWatchOptions, IWriteFileOptions, NotModifiedSinceFileOperationError, toFileOperationResult, toFileSystemProviderErrorCode, hasFileCloneCapability } from 'vs/platform/files/common/files'; </ins> import { readFileIntoStream } from 'vs/platform/files/common/io'; import { ILogService } from 'vs/platform/log/common/log';