fix: Check for Flagship's downloadFile method support before calling it

Previous implementation would not be backward compatible with older
Flagship app versions

By checking for method availability, we ensure the code is called only
on the correct Flagship app versions, otherwise the old process is
called

Related PR: #1518

packages/cozy-client/src/models/file.js

@@ -719,7 +719,12 @@ export const downloadFile = async ({ client, file, url, webviewIntent }) => {
   const filesCollection = client.collection(DOCTYPE_FILES)
 
   if (isFlagshipApp() && webviewIntent && !isEncrypted(file)) {
-    return await webviewIntent.call('downloadFile', file)
+    const isFlagshipDownloadAvailable =
+      (await webviewIntent?.call('isAvailable', 'downloadFile')) ?? false
+
+    if (isFlagshipDownloadAvailable) {
+      return await webviewIntent.call('downloadFile', file)
+    }
   }
 
   if (isEncrypted(file)) {

packages/cozy-client/src/models/file.spec.js

@@ -892,7 +892,7 @@ describe('downloadFile', () => {
   it('should handle download in Flagship app', async () => {
     isFlagshipApp.mockReturnValue(true)
     const webviewIntent = {
-      call: jest.fn()
+      call: jest.fn().mockResolvedValue(true)
     }
 
     const file = {
@@ -911,9 +911,42 @@ describe('downloadFile', () => {
     })
 
     expect(downloadFromCozySpy).not.toHaveBeenCalled()
+    expect(webviewIntent.call).toHaveBeenCalledWith(
+      'isAvailable',
+      'downloadFile'
+    )
     expect(webviewIntent.call).toHaveBeenCalledWith('downloadFile', file)
   })
 
+  it('should download files from web page in old Flagship app versions', async () => {
+    isFlagshipApp.mockReturnValue(true)
+    const webviewIntent = {
+      call: jest.fn().mockResolvedValue(false) // `isAvailable` returns `false` when not implemented
+    }
+
+    const file = {
+      _id: 'SOME_FILE_ID',
+      _type: 'io.cozy.file',
+      name: 'SOME_FILE_NAME'
+    }
+
+    await fileModel.downloadFile({
+      // @ts-ignore
+      client: cozyClient,
+      // @ts-ignore
+      file,
+      // @ts-ignore
+      webviewIntent
+    })
+
+    expect(downloadFromCozySpy).toHaveBeenCalled()
+    expect(webviewIntent.call).toHaveBeenCalledWith(
+      'isAvailable',
+      'downloadFile'
+    )
+    expect(webviewIntent.call).not.toHaveBeenCalledWith('downloadFile', file)
+  })
+
   it('should download encrypted files from web page as this is not supported yet by Flagship app', async () => {
     isFlagshipApp.mockReturnValue(true)
     const webviewIntent = {