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‎jsony.nimble‎

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version = "0.0.0"
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author = "Andre von Houck"
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description = "A loose direct to object json parser with hooks."
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license = "MIT"
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srcDir = "src"
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requires "nim >= 1.2.2"

‎src/jsony.nim‎

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import macros, strutils
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type JsonError = object of ValueError
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const whiteSpace = {' ', '\n', '\t', '\r'}
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proc parseJson[T](s: string, i: var int, v: var seq[T])
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proc parseJson[T:enum](s: string, i: var int, v: var T)
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proc parseJson[T:object|ref object](s: string, i: var int, v: var T)
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template error(msg: string) =
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## Short cut to raise an exception.
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raise newException(JsonError, msg)
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proc eatSpace(s: string, i: var int) =
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## Will consume white space.
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while i < s.len:
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let c = s[i]
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if c in whiteSpace:
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discard
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else:
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return
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inc i
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proc eat(s: string, i: var int, c: char) =
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## Will consume space before and then the character `c`.
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## Will raise an exception if `c` is not found.
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eatSpace(s, i)
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if i >= s.len:
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error("Expected " & c & " but end reached.")
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if s[i] == c:
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inc i
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else:
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error("Expected " & c & " at offset " & $i & ".")
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proc parseSymbol(s: string, i: var int): string =
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## Will read a symbol and return it.
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## Used for numbers and booleans.
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eatSpace(s, i)
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var j = i
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while i < s.len:
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case s[i]
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of ',', '}', ']', whiteSpace:
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break
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else:
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discard
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inc i
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return s[j ..< i]
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proc parseJson(s: string, i: var int, v: var bool) =
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## Will parse boolean true or false.
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case parseSymbol(s, i)
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of "true":
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v = true
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of "false":
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v = false
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else:
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error("Boolean true or false expected at offset " & $i & ".")
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proc parseJson(s: string, i: var int, v: var SomeInteger) =
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## Will parse int8, uint8, int16, uint16, int32, uint32, int64, uint64 or
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## just int.
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v = type(v)(parseInt(parseSymbol(s, i)))
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proc parseJson(s: string, i: var int, v: var SomeFloat) =
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## Will parse float32 and float64.
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v = type(v)(parseFloat(parseSymbol(s, i)))
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proc parseJson(s: string, i: var int, v: var string) =
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## Parse string.
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eat(s, i, '"')
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var j = i
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while i < s.len:
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case s[i]
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of '"':
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v = s[j ..< i]
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break
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else:
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discard
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inc i
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eat(s, i, '"')
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proc parseJson[T](s: string, i: var int, v: var seq[T]) =
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## Parse seq.
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eat(s, i, '[')
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while i < s.len:
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eatSpace(s, i)
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if s[i] == ']':
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break
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var element: T
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parseJson(s, i, element)
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v.add(element)
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eatSpace(s, i)
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if s[i] == ',':
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inc i
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else:
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break
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eat(s, i, ']')
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proc skipValue(s: string, i: var int) =
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## Used to skip values of extra fields.
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eatSpace(s, i)
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if s[i] == '{':
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eat(s, i, '{')
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while i < s.len:
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eatSpace(s, i)
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if s[i] == '}':
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break
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skipValue(s, i)
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eat(s, i, ':')
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skipValue(s, i)
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eatSpace(s, i)
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if s[i] == ',':
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inc i
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eat(s, i, '}')
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elif s[i] == '[':
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eat(s, i, '[')
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while i < s.len:
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eatSpace(s, i)
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if s[i] == ']':
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break
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skipValue(s, i)
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eatSpace(s, i)
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if s[i] == ',':
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inc i
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eat(s, i, ']')
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elif s[i] == '"':
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eat(s, i, '"')
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while i < s.len:
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inc i
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if s[i] == '"':
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break
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eat(s, i, '"')
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else:
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discard parseSymbol(s, i)
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proc camelCase(s: string): string =
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return s
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proc snakeCase(s: string): string =
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var prevCap = false
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for i, c in s:
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if c in {'A'..'Z'}:
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if result.len > 0 and result[^1] != '_' and not prevCap:
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result.add '_'
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prevCap = true
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result.add c.toLowerAscii()
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else:
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prevCap = false
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result.add c
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macro fieldsMacro(v: typed, key: string) =
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## Crates a parser for object fields.
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result = nnkCaseStmt.newTree(ident"key")
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# Get implementation of v's type.
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var impl = getTypeImpl(v)
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# Walk refs and pointers to the real type.
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while impl.kind in {nnkRefTy, nnkPtrTy}:
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impl = getTypeImpl(impl[0])
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# For each field in the type:
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var used: seq[string]
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for f in impl[2]:
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# Get fields name and type information.
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let fieldName = f[0]
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let filedNameStr = fieldName.strVal()
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let filedType = f[1]
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# Output a name/type checker for it:
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for fn in [camelCase, snakeCase]:
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let caseName = fn(filedNameStr)
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if caseName in used:
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continue
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used.add(caseName)
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let ofClause = nnkOfBranch.newTree(newLit(caseName))
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let body = quote:
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var value: `filedType`
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parseJson(s, i, value)
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v.`fieldName` = value
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ofClause.add(body)
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result.add(ofClause)
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let ofElseClause = nnkElse.newTree()
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let body = quote:
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skipValue(s, i)
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ofElseClause.add(body)
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result.add(ofElseClause)
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proc parseJson[T:enum](s: string, i: var int, v: var T) =
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eatSpace(s, i)
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var strV: string
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if s[i] == '"':
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parseJson(s, i, strV)
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when compiles(enumHook[T](strV)):
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v = enumHook[T](strV)
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else:
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v = parseEnum[T](strV)
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else:
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strV = parseSymbol(s, i)
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v = T(parseInt(strV))
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proc parseJson[T:object|ref object](s: string, i: var int, v: var T) =
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## Parse an object.
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eat(s, i, '{')
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when compiles(newHook(v)):
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newHook(v)
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elif compiles(new(v)):
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new(v)
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while i < s.len:
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eatSpace(s, i)
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if s[i] == '}':
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break
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var key: string
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parseJson(s, i, key)
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eat(s, i, ':')
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fieldsMacro(v, key)
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eatSpace(s, i)
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if s[i] == ',':
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inc i
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else:
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break
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eat(s, i, '}')
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proc fromJson*[T](s: string): T =
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## Takes json and outputs the object it represents.
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## * Create little intermediate values.
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## * Extra json fields are ignored.
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## * Missing json fields keep their default values.
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## * `proc newHook(foo: var ...)` Can be used to populate default values.
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var i = 0
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parseJson(s, i, result)

‎tests/config.nims‎

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--path:"../src"

‎tests/test_basic.nim‎

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import jsony
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block:
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doAssert fromJson[bool]("true") == true
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doAssert fromJson[bool]("false") == false
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doAssert fromJson[bool](" true ") == true
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doAssert fromJson[bool](" false ") == false
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doAssert fromJson[int]("1") == 1
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doAssert fromJson[int]("12") == 12
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doAssert fromJson[int](" 123 ") == 123
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doAssert fromJson[int8](" 123 ") == 123
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doAssert fromJson[uint8](" 123 ") == 123
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doAssert fromJson[int16](" 123 ") == 123
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doAssert fromJson[uint16](" 123 ") == 123
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doAssert fromJson[int32](" 123 ") == 123
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doAssert fromJson[uint32](" 123 ") == 123
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doAssert fromJson[int64](" 123 ") == 123
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doAssert fromJson[uint64](" 123 ") == 123
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doAssert fromJson[int8](" -99 ") == -99
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doAssert fromJson[int16](" -99 ") == -99
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doAssert fromJson[int32](" -99 ") == -99
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doAssert fromJson[int64](" -99 ") == -99
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doAssert fromJson[float32](" 1.34E3 ") == 1.34E3
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doAssert fromJson[float32](" 1.34E3 ") == 1.34E3
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doAssert fromJson[float64](" -1.34E3 ") == -1.34E3
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doAssert fromJson[float64](" -1.34E3 ") == -1.34E3
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block:
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doAssert fromJson[seq[int]]("[1, 2, 3]") == @[1, 2, 3]
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doAssert fromJson[seq[string]]("""["hi", "bye", "maybe"]""") ==
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@["hi", "bye", "maybe"]
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doAssert fromJson[seq[seq[string]]]("""[["hi", "bye"], ["maybe"], []]""") ==
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@[@["hi", "bye"], @["maybe"], @[]]

‎tests/test_enums.nim‎

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import jsony
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type Color = enum
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cRed
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cBlue
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cGreen
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doAssert fromJson[Color]("0") == cRed
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doAssert fromJson[Color]("1") == cBlue
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doAssert fromJson[Color]("2") == cGreen
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doAssert fromJson[Color](""" "cRed" """) == cRed
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doAssert fromJson[Color](""" "cBlue" """) == cBlue
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doAssert fromJson[Color](""" "cGreen" """) == cGreen
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type Color2 = enum
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c2Red
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c2Blue
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c2Green
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proc enumHook[Color2](v: string): Color2 =
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case v:
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of "RED": c2Red
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of "BLUE": c2Blue
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of "GREEN": c2Green
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else: c2Red
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doAssert fromJson[Color2](""" "RED" """) == c2Red
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doAssert fromJson[Color2](""" "BLUE" """) == c2Blue
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doAssert fromJson[Color2](""" "GREEN" """) == c2Green

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