microg/GmsCore · error · IllegalArgumentException

Not a bytes type

Error message

Not a bytes type

What it means

Flag.getBytes() throws IllegalArgumentException("Not a bytes type") when the flag's dataType is not DATA_TYPE_BYTES. The bytes accessor validates the dataType discriminator before returning bytesValue; reading byte-array content from any other kind of flag is rejected as a caller bug.

Source

Thrown at play-services-phenotype/src/main/java/com/google/android/gms/phenotype/Flag.java:95

        throw new IllegalArgumentException("Not a boolean type");
    }

    public double getDouble() {
        if (dataType == DATA_TYPE_DOUBLE)
            return doubleValue;
        throw new IllegalArgumentException("Not a double type");
    }

    public String getString() {
        if (dataType == DATA_TYPE_STRING)
            return stringValue;
        throw new IllegalArgumentException("Not a String type");
    }

    public byte[] getBytes() {
        if (dataType == DATA_TYPE_BYTES)
            return bytesValue;
        throw new IllegalArgumentException("Not a bytes type");
    }

    public static final int DATA_TYPE_LONG = 1;
    public static final int DATA_TYPE_BOOL = 2;
    public static final int DATA_TYPE_DOUBLE = 3;
    public static final int DATA_TYPE_STRING = 4;
    public static final int DATA_TYPE_BYTES = 5;

    public static final Creator<Flag> CREATOR = findCreator(Flag.class);
}

View on GitHub (pinned to 157c9d86ac)

Solutions

1. Guard with flag.getDataType() == Flag.DATA_TYPE_BYTES before calling getBytes()
2. If the flag may be a string, fall back to flag.getString().getBytes(StandardCharsets.UTF_8)
3. Switch over DATA_TYPE_* constants and handle the BYTES case explicitly
4. Verify the server-side flag is defined as a bytes/bytearray type

Example fix

// before
byte[] raw = flag.getBytes();
// after
byte[] raw = flag.getDataType() == Flag.DATA_TYPE_BYTES
    ? flag.getBytes()
    : flag.getString().getBytes(StandardCharsets.UTF_8);

if (flag.getDataType() != Flag.DATA_TYPE_BYTES) { throw new IllegalStateException("flag is not bytes: " + flag.getDataType()); }

static boolean isBytesFlag(Flag f) { return f != null && f.getDataType() == Flag.DATA_TYPE_BYTES; }

try { byte[] v = flag.getBytes(); } catch (IllegalArgumentException e) { log.warn("Flag type mismatch", e); v = EMPTY_BYTES; }

When it happens

Trigger: Calling Flag.getBytes() on a Flag whose dataType is DATA_TYPE_LONG (1), DATA_TYPE_BOOL (2), DATA_TYPE_DOUBLE (3), or DATA_TYPE_STRING (4) instead of DATA_TYPE_BYTES (5).

Common situations: Assuming a binary/certificate-style flag is stored as bytes when the server defines it as a string; generic flag iteration that calls getBytes() unconditionally; confusion between string and bytes flags after a server config change.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Not a long type
• Not a boolean type
• Not a double type
• Not a String type
• remoteBinder is the wrong class.

AI-assisted analysis of microg/GmsCore@157c9d86ac (2026-09-06). Data as JSON: /api/errors/0c2d41e21ad9762a. Report an issue: GitHub.