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preserves-nim
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Do not throw from preserveTo or fromPreserve 

Return an Option or boolean value. This makes it cheap to test if
a Preserves value is convertable to a Nim type.
This commit is contained in:
Emery Hemingway 2021-08-25 13:49:35 +02:00
parent 8341360741
commit d67482fad8
2 changed files with 114 additions and 52 deletions
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159
src/preserves.nim
View File

@ -2,7 +2,7 @@
# SPDX-License-Identifier: ISC
import bigints
import std/[base64, endians, hashes, macros, sets, streams, strutils, tables, typetraits]
import std/[base64, endians, hashes, macros, options, sets, streams, strutils, tables, typetraits]
import json except `%`, `%*`
@ -223,13 +223,14 @@ proc concat(result: var string; prs: Preserve) =
result.add('}')
of pkDictionary:
result.add('{')
var i = 0
for (key, value) in prs.dict.pairs:
if i > 0:
result.add(' ')
result.concat(key)
result.add(": ")
result.concat(value)
result.add(' ')
if prs.dict.len > 1:
result.setLen(result.high)
inc i
result.add('}')
of pkEmbedded:
result.add(prs.embedded.repr)
@ -256,6 +257,9 @@ func isRecord*(prs: Preserve): bool =
result = true
assert(prs.record.len > 0)
func isDictionary*(prs: Preserve): bool =
prs.kind == pkDictionary
proc label*(prs: Preserve): Preserve {.inline.} =
## Return the label of a record value.
prs.record[prs.record.high]
@ -572,25 +576,27 @@ macro `%*`*(x: untyped): untyped =
template record*(label: string) {.pragma.}
## Serialize this object or tuple as a record.
##
## ```
## type Foo {.record: "foobar".} = tuple
## a, b: int
## let r: Foo = (1, 2)
## echo $(toPreserve(r))
## # <foobar 1 2>
## assert($r.toPreserve == "<foobar 1 2>")
## ```
template unpreservable*() {.pragma.}
## Pragma to forbid a type from being converted by `toPreserve`.
proc toPreserve*[T](x: T): Preserve =
## Serializes `x` to Preserves; uses `toPreserveHook(x: A)` if it's in scope to
## Serializes `x` to Preserves; uses `toPreserveHook(x: T)` if it's in scope to
## customize serialization.
when T is Preserve: result = x
elif T is Bigint:
result = Preserve(kind: pkBigInteger, bigint: x)
elif compiles(toPreserveHook(x)):
result = toPreserveHook(x)
elif T is Bigint:
result = Preserve(kind: pkBigInteger, bigint: x)
elif T is seq[byte]:
result = Preserve(kind: pkByteString, bytes: x)
elif T is array | seq:
result = Preserve(kind: pkSequence)
for v in x.items: result.sequence.add(toPreserve(v))
@ -620,8 +626,10 @@ proc toPreserve*[T](x: T): Preserve =
result = Preserve(kind: pkString, string: x)
elif T is SomeInteger:
result = Preserve(kind: pkSignedInteger, int: x.BiggestInt)
else:
elif compiles(%x):
result = %x
else:
raiseAssert("unpreservable type" & $T)
proc toPreserveHook*[T](set: HashSet[T]): Preserve =
Preserve(kind: pkSet, set: set.map(toPreserve))
@ -697,66 +705,119 @@ proc toJsonHook*(prs: Preserve): JsonNode =
of pkEmbedded:
raise newException(ValueError, "cannot convert embedded value to JSON")
proc checkRecordLabel(T: typedesc; prs: Preserve) =
when T.hasCustomPragma(record):
const label = symbol(T.getCustomPragmaVal(record))
if prs.label != label:
raise newException(ValueError, $prs & " is not a record of class " & label.string)
else:
raise newException(Defect, $T & " lacks a {.record: \"…\".} annotation")
proc fromPreserve*[T](v: var T; prs: Preserve): bool =
## Inplace version of `preserveTo`.
## Partial matches on compond values may leave artifacts in ``v``.
# TODO: {.raises: [].}
runnableExamples:
import std/options, preserves, preserves/parse
type Foo {.record: "foo".} = object
x, y, z: int
proc fromPreserve*[T](result: var T; prs: Preserve) =
# Inplace version of `preserveTo`.
when compiles(fromPreserveHook(result, prs)):
fromPreserveHook(result, prs)
var foo: Foo
assert(fromPreserve(foo, parsePreserves("""<foo 1 2 3>""")))
assert(foo.x == 1)
assert(foo.y == 2)
assert(foo.z == 3)
when compiles(fromPreserveHook(v, prs)):
result = fromPreserveHook(v, prs)
elif T is Preserve:
result = prs
v = prs
result = true
elif T is Bigint:
result = prs.bigint
case prs.kind
of pkSignedInteger:
v = initBigint(prs.int)
result = true
of pkBigInteger:
v = prs.bigint
result = true
else: disard
elif T is bool:
result = prs.bool
if prs.kind == pkBoolean:
v = prs.bool
result = true
elif T is SomeInteger:
result = T(prs.int)
if prs.kind == pkSignedInteger:
v = T(prs.int)
result = true
elif T is float:
result = prs.float
if prs.kind == pkFloat:
v = prs.float
result = true
elif T is seq:
result.setLen(prs.sequence.len)
for i, val in prs.sequence:
fromPreserve(result[i], val)
if T is seq[byte] and prs.kind == pkByteString:
v = prs.bytes
result = true
elif prs.kind == pkSequence:
v.setLen(prs.len)
result = true
for i, e in prs.sequence:
result = result and fromPreserve(v[i], e)
elif T is float64:
result = prs.double
case prs.kind
of pkFloat:
v = prs.float
result = true
of pkDouble:
v = prs.double
result = true
elif T is object | tuple:
case prs.kind
of pkRecord:
# checkRecordLabel(T, prs)
var i: int
for k, v in result.fieldPairs:
fromPreserve(v, prs.record[i])
inc(i)
when T.hasCustomPragma(record):
const label = symbol(T.getCustomPragmaVal(record))
if prs.record[prs.record.high] == label:
result = true
var i = 0
for fname, field in v.fieldPairs:
if not result or (i == prs.record.high): break
result = result and fromPreserve(field, prs.record[i])
inc(i)
result = result and (i == prs.record.high) # arity equivalence check=
of pkDictionary:
for k, v in result.fieldPairs:
fromPreserve(v, prs.dict[symbol(k)])
else:
raise newException(ValueError, "cannot convert to Preserves value to type " & $T)
result = true
for key, val in v.fieldPairs:
result = result and fromPreserve(val, prs.dict.getOrDefault(symbol(key)))
else: discard
elif T is Ordinal | SomeInteger:
result = (T)prs.int
if prs.kind == pkSignedInteger:
v = (T)prs.int
result = true
elif T is ref:
if prs != symbol"null":
new result
fromPreserve(result[], prs)
new v
result = fromPreserve(v[], prs)
elif T is string:
result = prs.string
if prs.kind == pkString:
v = prs.string
result = true
elif T is distinct:
fromPreserve(result.distinctBase, prs)
result = fromPreserve(result.distinctBase, prs)
else:
static: raiseAssert("cannot convert from Preserves: " & $T)
raiseAssert("no conversion of type Preserve to " & $T)
proc preserveTo*(prs: Preserve; T: typedesc): T =
proc preserveTo*(prs: Preserve; T: typedesc): Option[T] =
## Reverse of `toPreserve`.
fromPreserve(result, prs)
# TODO: {.raises: [].}
runnableExamples:
import std/options, preserves, preserves/parse
type Foo {.record: "foo".} = object
x, y, z: int
proc fromPreserveHook*[A,B](result: var Table[A,B]|TableRef[A,B]; prs: Preserve) =
for k, v in prs.pairs: result[preserveTo(k,A)] = preserveTo(k,B)
assert(parsePreserves("""<foo "abc">""").preserveTo(Foo).isNone)
assert(parsePreserves("""<bar 1 2 3>""").preserveTo(Foo).isNone)
assert(parsePreserves("""<foo 1 2 3>""").preserveTo(Foo).isSome)
var v: T
if fromPreserve(v, prs):
result = some(move v)
proc fromPreserveHook*[A,B](t: var Table[A,B]|TableRef[A,B]; prs: Preserve): bool =
if prs.isDictionary:
for k, v in prs.pairs:
t[preserveTo(k,A)] = preserveTo(k,B)
result = true
proc len*(prs: Preserve): int =
## Return the number of values one level below ``prs``.

7
tests/test_conversions.nim
View File

@ -1,6 +1,6 @@
# SPDX-License-Identifier: ISC
import streams, strutils, unittest
import std/[options, streams, strutils, unittest]
import bigints, preserves, preserves/records
suite "conversions":
@ -14,7 +14,7 @@ suite "conversions":
c: Foobar = (a: 1, b: 2, c: Bar(s: "ku",))
b = toPreserve(c)
a = preserveTo(b, Foobar)
check(a == c)
check(a.isSome and (get(a) == c))
check(b.kind == pkDictionary)
test "records":
@ -27,7 +27,8 @@ suite "conversions":
tup: Foobar = (a: 1, b: 2, c: Bar(s: "ku",))
prs = toPreserve(tup)
check(prs.kind == pkRecord)
check(preserveTo(prs, Foobar) == tup)
check($prs == """<foo 1 2 <bar "ku">>""")
check(preserveTo(prs, Foobar) == some(tup))
check(classOf(tup) == classOf(prs))
suite "%":