Crash in [RNFetchBlobFS readFile] on iOS

[cosmith]

Hi, I'm getting a crash when trying to send a file that doesn't exist anymore.

RNFetchBlob version 0.10.3, RN version 0.38.0

This is the stack trace I get:

#3  0x000000010ffd5fb4 in +[RNFetchBlobFS readFile:encoding:resolver:rejecter:onComplete:] at [APP]/node_modules/react-native-fetch-blob/ios/RNFetchBlobFS.m:426
#4  0x000000010ffe49f0 in __59+[RNFetchBlobReqBuilder buildFormBody:boundary:onComplete:]_block_invoke at [APP]/node_modules/react-native-fetch-blob/ios/RNFetchBlobReqBuilder.m:205
#5  0x000000010ffe3e42 in +[RNFetchBlobReqBuilder buildFormBody:boundary:onComplete:] at [APP]/node_modules/react-native-fetch-blob/ios/RNFetchBlobReqBuilder.m:251
#6  0x000000010ffe1843 in __89+[RNFetchBlobReqBuilder buildMultipartRequest:taskId:method:url:headers:form:onComplete:]_block_invoke at [APP]/node_modules/react-native-fetch-blob/ios/RNFetchBlobReqBuilder.m:54

It seems like the readFile method is called here and here with the resolver and rejecter set to nil.

The crash happens here:

react-native-fetch-blob/src/ios/RNFetchBlobFS.m

Line 448 in d702708

reject(@"RNFetchBlobFS readFile error", @"file not exists", nil);

                if(![[NSFileManager defaultManager] fileExistsAtPath:path]) {
                    reject(@"RNFetchBlobFS readFile error", @"file not exists", nil);
                    return;
                }

I don't know why the try/catch block in readFile doesn't catch the exception. I tried adding a if (reject != nil) condition before the call, which works, but then the call just fails silently...

Any thoughts?

[cosmith]

BTW I'd be happy to send a PR if someone can point me in the right direction.

[wkh237]

@cosmith , could you provide a sample that replicates this error? It'd be helpful for me to find a way to fix it 👍

[wkh237]

@cosmith , perhaps we can add a return; below [this line] (

react-native-fetch-blob/src/ios/RNFetchBlobFS.m

Line 455 in d702708

onComplete(fileContent);

) that looks reasonable to me because the function doesn't have to encode the file content when either resolver and rejector are nil (which means the call is from native context instead of JS).

__block Byte * buffer;
            if(asset != nil)
            {
                buffer = malloc(asset.size);
                [asset getBytes:buffer fromOffset:0 length:asset.size error:&err];
                if(err != nil)
                {
                    reject(@"RNFetchBlobFS readFile error", @"failed to read asset", [err localizedDescription]);
                    return;
                }
                fileContent = [NSData dataWithBytes:buffer length:asset.size];
                free(buffer);
            }
            else
            {
                if(![[NSFileManager defaultManager] fileExistsAtPath:path]) {

                    reject(@"RNFetchBlobFS readFile error", @"file not exists", nil);
                    return;
                }
                fileContent = [NSData dataWithContentsOfFile:path];

            }
            if(onComplete != nil)
+            {                                                                                                                                                      
+                onComplete(fileContent);                                                                                                    
+                return;                                                                                                                                                      
+            }                                                                                                                                                                                                        

[cosmith]

This is the function we use:

    static async sendFile(method, path, fileUri, fieldName, additionalData, onProgress = () => {}) {
        let token = await Storage.getUserProperty("token");

        let headers = {
            "Authorization": `Token ${token}`,
            "Content-Type": "multipart/form-data",
        };

        let source = fileUri.replace("file://", "");
        let file = RNFetchBlob.wrap(source);

        let formData = [
            {name: fieldName, filename: fieldName + ".png", data: file},
        ];

        for (let key in additionalData) {
            formData.push({name: key, data: String(additionalData[key])});
        }

        this.onLoadChange(true);
        return RNFetchBlob.fetch(method, Constants.ServerUrl + path, headers, formData)
            .uploadProgress((written, total) => {
                onProgress(written, total);
            })
            .then((response) => {
                this.onLoadChange(false);
                if (response.respInfo.status < 200 || response.respInfo.status > 399) {
                    Log.warn("[Server]", "error loading", path, response.data);
                    this.onLoadChange(false);
                    throw response;
                }
                return response.json();
            }, (error) => {
                this.onLoadChange(false);
                Log.warn("[Server]", "error making request", path, error);
                throw error;
            });
    }

Calling this function with a file that doesn't exist crashes:

Server.sendFile("POST", "/test/", "i-dont-exist.png", "photo", {});

Adding a return where you suggested doesn't fix the issue since the crash happens on line 448 (reject(@"RNFetchBlobFS readFile error", @"file not exists", nil);).

[wkh237]

@cosmith , I have committed a fix to issue-266 branch, could you try if that fix the issue?

$ npm install --save github:wkh237/react-native-fetch-blob-package#issue-266

[cosmith]

Yes that fixes it! Thanks 👍