Add serde_seq to serialize maps as a sequence #158
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| //! The default `serde` implementation serializes `IndexMap` as a normal map, | ||
| //! but there is no guarantee that serialization formats will preserve the order | ||
| //! of the key-value pairs. This module serializes `IndexMap` as a sequence of | ||
| //! `(key, value)` elements instead, in order. |
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I'm not sure whether serializing tuples is a good choice, although it's the easiest to implement. Alternatively, serde sequences may be heterogeneous, so we could use a flat sequence of key0, value0, key1, value1, ... instead. I don't know whether all serialization formats support that though.
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This is also just a helper, so we don't have to be perfect here. A third party can write a similar custom module with different choices, as there aren't issues like trait coherence for this.
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Yet another possibility is a pair of sequences, ([key, ...], [value, ...]), but when deserializing we would have to read keys into temporary storage before we start reading values and insert into the map.
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This seems good to support, I fear most users won't find this feature until after the first bug happens, but at least there's a solution then. |
Our default serde implementation treats `IndexMap` as a normal map, which is often a nice representation in serialization formats, but they might not preserve the order. This commit adds a `serde_seq` module with `serialize` and `deserialize` functions, which makes it suitable for serde's field attributes, like `#[serde(with = "indexmap::serde_seq")]`. This mode treats `IndexMap` as a sequence of `(key, value)` pairs, which should always preserve order.
Our default serde implementation treats
IndexMapas a normal map,which is often a nice representation in serialization formats, but they
might not preserve the order.
This commit adds a
serde_seqmodule withserializeanddeserializefunctions, which makes it suitable for serde's field attributes, like
#[serde(with = "indexmap::serde_seq")]. This mode treatsIndexMapasa sequence of
(key, value)pairs, which should always preserve order.Closes #156.