structio 0.7.0

Correctness fixes from a round of external review (#24 to #31): reading, validating, transcoding and framing now agree on the nesting limit and on what a BEVE value is, a failed read leaves nothing behind for a reader that retries, and json::Raw checks string escapes. One breaking change: a BEVE delimiter where a value belongs is now InvalidHeader everywhere.

[dependencies]
structio = "0.7"

# The derive is off by default:
structio = { version = "0.7", features = ["derive"] }

Changed

• A BEVE delimiter is never a value. validate_beve accepted a document that was only a delimiter, which no reader could read and no stream framed. Everywhere a value belongs, every walk now refuses one as InvalidHeader; between streamed documents it is still a separator. Breaking for code expecting UnsupportedFeature for a delimiter from a Value read or beve_to_json, or relying on a delimiter as an unknown member's value being stepped over.

Fixed

• A failed read no longer costs a reader that winds back and retries. Every reader that entered a nesting level kept it on an error path, so a speculating reader lost a level per failed attempt and, after 256, had ordinary input refused as ExceededMaxDepth. A failed internally tagged read with a late tag could also leave its held members behind for the next object at the same depth, which then read them as its own.

• json::Raw checks string escapes. Raw::new, Raw::from_string and a Raw field accepted "\q" or a lone "\ud800" and wrote it back out. They now refuse any escape the string reader refuses, with the same error. The number grammar is still not checked.

• A typed array read in one copy, borrowed, or read as a &[u8] is charged a nesting level, as every other walk charges it. A document one level from the limit read with from_beve but failed validate_beve, beve_to_json and framing, and a framing failure ends a Documents or Feed stream.

• -0 read into a Value lost its sign. It became the integer 0; it is now the float -0.0, as -0.0 and -0e0 already were and as an f64 reads it.

• A BEVE float read as an integer, or a 128-bit float read at all, no longer reports an offset past the value. Both are refused on the header before the payload is taken, so the cursor and Error::index stop just past the header, as every other type mismatch does.