fix: stream custom map imports from disk when the file supports it#197
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gmaclennan wants to merge 1 commit into
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fix: stream custom map imports from disk when the file supports it#197gmaclennan wants to merge 1 commit into
gmaclennan wants to merge 1 commit into
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Importing a custom map via useImportCustomMapFile uploaded the file with fetch, which on React Native (expo/fetch) reads the whole request body into memory before sending - large SMP files could exhaust memory. Add an uploadFile method to the map server API that uses the file's own upload method when it has one (e.g. expo-file-system's File.upload(), which streams the file from disk on both Android and iOS) and falls back to the existing fetch PUT otherwise, so web and electron are unaffected. Non-2xx upload responses are normalized to the same HTTPError thrown by the fetch path.
achou11
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July 23, 2026 17:04
achou11
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Jul 23, 2026
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Couple of non-blocking comments but otherwise lgtm
| // import function we accept an object with the compatible properties and | ||
| // methods, and for the expo File, which can represent a file that does not yet | ||
| // exists, we type the `exists` property so that we can check that. | ||
| export type CompatFile = Omit<File, 'lastModified' | 'webkitRelativePath'> |
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not necessary to export this type right now
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| export type CompatFile = Omit<File, 'lastModified' | 'webkitRelativePath'> | |
| type CompatFile = Omit<File, 'lastModified' | 'webkitRelativePath'> |
| } | ||
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| type ExpoFileWithUpload = ExpoFileDuckType & { | ||
| upload( |
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just noting that File.upload was added to Expo FileSystem in SDK 56:
https://docs.expo.dev/versions/v56.0.0/sdk/filesystem/#uploadurl-options
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| options?: { | ||
| headers?: Record<string, string> | ||
| httpMethod?: string | ||
| sessionType?: 'background' | 'foreground' | ||
| }, |
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just checking: none of the other options are relevant to us?
https://docs.expo.dev/versions/v56.0.0/sdk/filesystem/#uploadoptions
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Problem
useImportCustomMapFile()uploads the map file withfetch. On React Native the injectedexpo/fetchimplementation reads the whole request body into memory before sending (normalizeBodyInitAsyncconverts any Blob-shaped body, including an expo-file-systemFile, to aUint8Array— still the case in SDK 56). Large SMP files can exhaust memory, which is why comapeo-mobile currently carries a patch toexpo/fetchadding native file streaming. That patch is Android-only and has to be rebased on every SDK upgrade.Solution
expo-file-system's
File.upload()streams the file from disk on both platforms (OkHttpRequestBodystreaming from anInputStreamon Android,URLSession.uploadTask(fromFile:)on iOS), so we can use it instead of fetch when it's available.This adds an
uploadFilemethod to the internal map server API which duck-types the file: if it has anuploadmethod it is called with the resolved URL (httpMethod: 'PUT', andsessionType: 'foreground', since an iOS background session can't reach the in-process map server across app suspension); otherwise it falls back to the existing fetchPUT, so web and electron are unaffected (browser fetch already streamsFilebodies from disk). The mutation keeps its existing contract: it resolves with aResponseand rejects with anHTTPError(error details parsed from a JSON body when available) on non-2xx responses.With this, comapeo-mobile can drop its
expo/fetchpatch entirely.