Goal

Fix a bug when overwriting of clearing metadata, the NDK did not always remove the value as expected leading to phantom metadata values in reports. For example:

addMetadata("section", "overwrite", "value1")
addMetadata("section", "overwrite", "value2")
clearMetadata("section", "overwrite")

Would typically result in the Event having "value1" in its reported metadata, instead of no value as expected.

Design

Introduce a simple compacting function which will remove any duplicates and gaps in the metadata array and compact it.

This new function is used when either:

• an entry or entries are removed from the metadata
• the metadata array is full and a new value is being added

By retaining the insertion order of the metadata we introduce minimal additional overhead on the most common path: adding metadata. The correct values are retained as the most recent values are always the last in the array (effectively acting as a primitive journal).

Designs considered but not used

• A linear scan to check for existing values in the add functions - this would have introduce unacceptable overheads
• A full hash-map style implementation - requires a significant rewrite of the entire metadata model

Testing

Modified the existing end-to-end test which deletes metadata before a native crash