Error should point to the right spots where it fails to parse

[talegari]

Failed parsing shows like this:

box::use(sr = structr)
packageVersion("structr")
#> [1] '0.1.0.9000'

schema = sr$s_map(
  x = sr$s_integer(),
  y = sr$s_double(),
  z = sr$s_optional(sr$s_string())
  ) |>
  sr$build_structure()

json_str_1 = '{"x": 1.1, "y": 99.9, "z": "value"}'
sr$parse_json(json_str_1, schema)
#> Error in `sr$parse_json()`:
#> ! ExpectedSigned at character 0

^{Created on 2025-04-26 with reprex v2.1.1}

Error message could say something like "Expected an integer for x, but got a double". If x was nested in y, we could say "Expected foo at y$x, but got bar".

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structr fills a much needed void in the R ecosystem which was lacking pydantic like schema manager. Thanks for writing this.