export contacts to a .vcf fails with "ERROR: java.lang.illegal Argument Exception: jav..."

[DrDustwolf]

Checklist

• I can reproduce the bug with the latest version given here.
• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the bug report will be dismissed otherwise.
• This issue contains only one bug.
• I have read and understood the contribution guidelines.

Affected app version

1.6.0

Affected Android/Custom ROM version

LineageOS 22.2-20251202-microG-axolotl (Android 15)

Affected device model

SHIFT6mq (axolotl)

How did you install the app?

F-Droid

Steps to reproduce the bug

1: co to Settings
2: click on: export contacts to a .vcf file
3: click on: include contact sources
4: select: "DEVICE" (it's the same result if I include all sources)
5: click on: OK
6: click on: save (german: speichern)
7: The Error shows up "ERROR: java.lang.illegal Argument Exception: jav..."
8: the exported .vcf file (contacts_20260825_120500.vcf) is empty (0 Bytes)

Expected behavior

Expected behaviour:
create a backup of all contacts without problems, which can later be imported without bugs or errors.

Actual behavior

Actual behaviour:
One ends up with an empty .vcf file and the error: "ERROR: java.lang.illegal Argument Exception: jav..."

Screenshots/Screen recordings

Additional information

Additional information:
The bug exists a very long time (multiple years) unchanged. It was even there when the application was a part of Simple Mobile Tools and before Fossify was a thing. I hoped the next time I need to migrate to another device the problem would be fixed by someone else experiencing the same problem, but obviously it still hasn't. The last time I changed my phone to a newer model I needed to export just a few contacts one by one in order to circumvent the error from happening. I think the problem is caused by the number of contacts which I have (358 contacts as of today) and the amount of information inside some of them. I have noted a few infos like opening hours and similar things in some of them, in the "Notes" field.

[DrDustwolf]

Log capture for the VCF export crash:

Captured via adb logcat --pid= while triggering "Export contacts to a .vcf file" in Fossify Contacts. The app was already open when logcat started. Log contains only org.fossify.contacts output. No personal data present (verified via grep for emails, phone numbers, vCard name/address/note fields, IMEI/serial).

Affected app version

1.6.0

Number of contacts

358

Affected Android/Custom ROM version

LineageOS 22.2-20251202-microG-axolotl (Android 15)

Affected device model

SHIFT6mq (axolotl)

How did you install the app?

F-Droid

Steps to reproduce the bug

Opened Fossify Contacts

adb logcat -c

adb logcat --pid=$(adb shell pidof org.fossify.contacts) > fossify.log

Triggered export → error appeared

Ctrl+\ to stop logcat

fossify.log

[DrDustwolf]

Follow-up – full investigation results:

1. Logcat capture

Captured via adb logcat --pid=$(adb shell pidof org.fossify.contacts) while triggering "Export contacts to a .vcf file". The log contains only org.fossify.contacts output (filtered by PID). No personal data present (verified via grep for emails, phone numbers, vCard name/address/note fields, IMEI/serial).

The log reveals java.io.FileNotFoundException: No content provider: (empty URI) repeated for every contact during export. The IllegalArgumentException shown in the UI does NOT appear in logcat – it is caught internally and only displayed as a UI message.

2. Contact photo analysis (sqlite on contacts2.db)

    All 58 photo entries in the DB have an empty PHOTO_FILE_ID (data14 is NULL/empty), yet 45 photo files exist in /data/data/com.android.providers.contacts/files/photos/ (all valid JPEGs).

    Removing all contact photos in Fossify did NOT fix the export – the issue persists.

    Conclusion: The FileNotFoundException entries in logcat are normal warning-level logs (Fossify attempts to load a thumbnail for every contact). They are not the root cause of the export crash.

3. Notes analysis

Searched all note fields for quotes/backslashes (GLOB '*["\\]*'). Found 7 contacts with special characters in notes (largest: 30,869 chars). Cleared all 7 notes → export still fails. Notes are not the trigger.

4. Phone/E-mail label analysis

Searched all phone and email label fields (data2) for quotes/backslashes → zero results. Labels are clean.

5. Bisecting

    10 selected contacts → export succeeds

    50 random contacts (excluding the known problematic one) → export succeeds

    255 random contacts → export fails intermittently (depends on which contacts are selected)

    A–M (96/358) → export succeeds

    N–Z → export fails

6. Root cause identified

The problematic contact is an aggregated contact combining multiple raw contacts from different sources:

    4× Telegram (synced)

    1× Device

    1× "Phone storage (not visible to other apps)"

This results in 5 photo entries for a single contact (one per raw contact), of which 4 have an empty PHOTO_FILE_ID but a non-empty thumbnail BLOB.

The contact alone reliably triggers the crash. Selecting all contacts except this one still fails → there is at least one additional problematic contact in N–Z (likely also an aggregated contact with the same structure).

7. Hypothesis

Fossify iterates over all raw contacts of an aggregated contact during vCard serialization. When a raw contact originates from "Phone storage (not visible to other apps)", its field values (e.g. PHOTO_FILE_ID) are empty/null. Fossify does not perform a null-check before attempting to open the URI, causing the crash.

Suggested fix: Skip raw contacts from inaccessible sources during export, or add null-checks for all field values before serializing them into the vCard.


Happy to test further (e.g. providing the exact raw contact structure, testing with a minimal reproduction contact, etc.) if that would help.

fossify_nofotos.log

[DrDustwolf]

Update – test results:

The problematic contact reliably reproduces the crash when selected alone for export. It is an aggregated contact with multiple raw contacts from different sources (4× Telegram, 1× Device, 1× "Phone storage (not visible to other apps)").

DB structure of the problematic contact:

    name ×1 (data1 empty)

    photo ×5 (4 with empty data14 + thumbnail BLOB in data15, 1 with data14=34)

    nickname ×1 (data1 empty)

    phone_v2 ×1 (data1=17 chars, label, data4=13)

    email_v2 ×2 (data1=26/16 chars, label, data3=7/4)

    postal-address_v2 ×2 (data1=60/90 chars, label, data3=0/4, data4=60/90)

    im ×4 (data1=25/24/18/14 chars, protocol in data3)

    note ×1 (data1=10,825 chars)

    organization ×1 (data1=59 chars)

    website ×2 (data1=35/32 chars)

Ruled out as the trigger:

    Contact photos (all removed → crash persists)

    Note fields (all 7 contacts with special characters in notes cleared → crash persists)

    Phone/email labels (no quotes or backslashes found via sqlite)

    The "Phone storage (not visible)" raw contact specifically (removed → crash persists)

Not conclusively tested:

    Whether the aggregation itself (2+ raw contacts) is the trigger. Attempted to remove the Telegram raw contacts via sqlite, but Nekogram re-syncs them automatically, making the test inconclusive.

Environment: LineageOS 22.2 (Android 15), MicroG, rooted. Total contacts: 358.

Happy to provide a sqlite dump of just this contact (personal data redacted) or test further if needed.