initial

Author: glennsl

.gitignore

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+.DS_Store
+.idea
+*.log
+tmp/
+
+.bsb.lock
+.merlin
+lib/
+node_modules/

bsconfig.json

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+{
+  "name": "@glennsl/rescript-json-combinators",
+  "namespace": "JsonCombinators",
+  "sources": [
+    "src",
+    {
+      "dir": "examples",
+      "type": "dev"
+    }
+  ]
+}

package-lock.json

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+{
+  "name": "@glennsl/rescript-json-combinators",
+  "version": "1.0.0",
+  "description": "Combinator library for JSON decoding and encoding. ",
+  "scripts": {
+    "build": "rescript build -with-deps",
+    "start": "rescript build -w -with-deps",
+    "clean": "rescript clean",
+    "fmt": "rescript format -all"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/glennsl/rescript-json-combinators.git"
+  },
+  "keywords": ["rescript", "json"],
+  "author": "glennsl",
+  "license": "(LGPL-3.0 OR MPL-2.0)",
+  "bugs": {
+    "url": "https://github.com/glennsl/rescript-json-combinators/issues"
+  },
+  "homepage": "https://github.com/glennsl/rescript-json-combinators#readme",
+  "files": ["src/*.res*", "bsconfig.json"],
+  "devDependencies": {
+    "rescript": "^9.1.4"
+  }
+}

package.json

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+open Js.Json
+
+type t<'a> = (. Js.Json.t) => 'a
+
+type fieldDecoders = {
+  optional: 'a. (. string, t<'a>) => option<'a>,
+  required: 'a. (. string, t<'a>) => 'a,
+}
+
+exception DecodeError(string)
+
+module Error = {
+  let expected = (kind, json) => raise(DecodeError(`Expected ${kind}, got ${stringify(json)}`))
+}
+
+let custom = f => f
+
+let float = (. json) => {
+  if Js.typeof(json) != "number" {
+    Error.expected("float", json)
+  }
+
+  Obj.magic(json)
+}
+
+let int = (. json) => {
+  if Js.typeof(json) != "number" {
+    Error.expected("int", json)
+  }
+
+  let truncated: float = %raw("json | 0")
+  let num: float = Obj.magic(json)
+  if truncated != num || !Js.Float.isFinite(num) {
+    Error.expected("int", json)
+  }
+
+  Obj.magic(json)
+}
+
+let bool = (. json) => {
+  if Js.typeof(json) != "boolean" {
+    Error.expected("bool", json)
+  }
+
+  Obj.magic(json)
+}
+
+let string = (. json) => {
+  if Js.typeof(json) != "string" {
+    Error.expected("string", json)
+  }
+
+  Obj.magic(json)
+}
+
+let array = (decode, . json) => {
+  if !Js.Array.isArray(json) {
+    Error.expected("array", json)
+  }
+
+  let source: array<Js.Json.t> = Obj.magic(json)
+  let target = %raw("new Array(json.length)")
+
+  for i in 0 to Array.length(source) - 1 {
+    try {
+      let value = decode(. %raw("json[i]"))
+      target->Array.unsafe_set(i, value)
+    } catch {
+    | DecodeError(msg) => raise(DecodeError(j`${msg}\n\tin array at index $i`))
+    }
+  }
+
+  target
+}
+
+let pair = (decodeA, decodeB, . json) => {
+  if !Js.Array.isArray(json) {
+    Error.expected("array", json)
+  }
+
+  let arr: array<Js.Json.t> = Obj.magic(json)
+  if Array.length(arr) != 2 {
+    raise(
+      DecodeError(
+        `Expected array of length 2, got array of length ${Array.length(arr)->string_of_int}`,
+      ),
+    )
+  }
+
+  try (decodeA(. arr->Array.unsafe_get(0)), decodeB(. arr->Array.unsafe_get(1))) catch {
+  | DecodeError(msg) => raise(DecodeError(j`${msg}\n\tin pair`))
+  }
+}
+
+let option = (decode, . json) => {
+  if Obj.magic(json) == Js.null {
+    None
+  } else {
+    Some(decode(. json))
+  }
+}
+
+let field = (key, decode, . json) => {
+  if Js.typeof(json) != "object" || Js.Array.isArray(json) || Obj.magic(json) == Js.null {
+    Error.expected("object", json)
+  }
+
+  if !(%raw("key in json")) {
+    raise(DecodeError(`${key} required`))
+  }
+
+  try decode(. %raw("json[key]")) catch {
+  | DecodeError(msg) => raise(DecodeError(`${msg}\n\tat field '${key}'`))
+  }
+}
+
+let object = (f, . json) => {
+  if Js.typeof(json) != "object" || Js.Array.isArray(json) || Obj.magic(json) == Js.null {
+    raise(Error.expected("object", json))
+  }
+
+  let optional = (. key, decode) => {
+    if !(%raw("key in json")) {
+      None
+    } else {
+      try {
+        let value = decode(. %raw("json[key]"))
+        Some(value)
+      } catch {
+      | DecodeError(msg) => raise(DecodeError(`${msg}\n\tat field '${key}'`))
+      }
+    }
+  }
+
+  let required = (. key, decode) => {
+    if !(%raw("key in json")) {
+      raise(DecodeError(`${key} required`))
+    }
+
+    try decode(. %raw("json[key]")) catch {
+    | DecodeError(msg) => raise(DecodeError(`${msg}\n\tat field '${key}'`))
+    }
+  }
+
+  f({optional: optional, required: required})
+}
+
+let oneOf = (decoders, . json) => {
+  let errors = []
+
+  let rec loop = i => {
+    if i >= Array.length(decoders) {
+      raise(
+        DecodeError(
+          `All decoders given to oneOf failed. Here are all the errors:\n- ${errors->Js.Array2.joinWith(
+              "\n",
+            )}\nAnd the JSON being decoded: ${stringify(json)}`,
+        ),
+      )
+    }
+
+    let decode = Array.unsafe_get(decoders, i)
+    try decode(. json) catch {
+    | DecodeError(err) =>
+      errors->Js.Array2.push(err)->ignore
+      loop(i + 1)
+    }
+  }
+
+  loop(0)
+}
+
+let map = (decode, f, . json) => f(. decode(. json))
+
+let decode = (json, decode) =>
+  try Ok(decode(. json)) catch {
+  | DecodeError(msg) => Error(msg)
+  }

src/Decode.res

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+type t<'a>
+
+type fieldDecoders = {
+  optional: 'a. (. string, t<'a>) => option<'a>,
+  required: 'a. (. string, t<'a>) => 'a,
+}
+
+exception DecodeError(string)
+
+module Error: {
+  let expected: (string, Js.Json.t) => _
+}
+
+let custom: ((. Js.Json.t) => 'a) => t<'a>
+
+let float: t<float>
+let int: t<int>
+let bool: t<bool>
+let string: t<string>
+let array: t<'a> => t<array<'a>>
+let pair: (t<'a>, t<'b>) => t<('a, 'b)>
+let option: t<'a> => t<option<'a>>
+let field: (string, t<'a>) => t<'a>
+let object: (fieldDecoders => 'a) => t<'a>
+
+let oneOf: array<t<'a>> => t<'a>
+let map: (t<'a>, (. 'a) => 'b) => t<'b>
+
+let decode: (Js.Json.t, t<'a>) => result<'a, string>

src/Decode.resi

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+external int: int => Js.Json.t = "%identity"
+external float: float => Js.Json.t = "%identity"
+external bool: bool => Js.Json.t = "%identity"
+external string: string => Js.Json.t = "%identity"
+
+module Unsafe = {
+  external object: {..} => Js.Json.t = "%identity"
+}