WebToolArcUse this result with confidence
Define the path grammar before unflattening
A key such as a.b[0].c can represent nested objects and arrays only when the producer and consumer agree on the grammar. Dots, brackets, escaped delimiters, and literal key characters can be ambiguous. Choose the path style deliberately and keep one sample that exercises arrays, numeric-looking keys, and delimiter characters.
Conflicts are data-model decisions, not formatting errors
A flat map can ask the same path to be both a scalar and a container, for example a=1 alongside a.b=2. No unflattener can satisfy both meanings without a policy. Detect those collisions, decide which source wins, and document the rule rather than silently overwriting a value.
Verify with a round trip when interoperability matters
After rebuilding nested JSON, flatten it again with the same path rules and compare the resulting key/value pairs. A successful parse is not enough: arrays, nulls, empty objects, and numeric indexes can change shape while still producing valid JSON. Keep a round-trip fixture for integrations.
Preserve types through the handoff
Flat inputs often arrive as strings even when downstream JSON expects booleans, numbers, null, or structured values. Decide whether values should remain strings or be parsed before unflattening. Type inference can be convenient for one dataset and destructive for another, so keep the conversion rule visible.