feat: add support for Decimal scalar (#96)

Co-authored-by: Jason Kuhrt <jasonkuhrt@me.com>

README.md

@@ -124,7 +124,7 @@ export const schema = makeSchema({
 ##### Shortterm
 
 - [x] ([#59](https://github.com/prisma/nexus-prisma/issues/59)) Support for Prisma Model field type `BigInt`
-- [ ] ([#94](https://github.com/prisma/nexus-prisma/issues/94)) Support for Prisma Model field type `Decimal`
+- [x] ([#94](https://github.com/prisma/nexus-prisma/issues/94)) Support for Prisma Model field type `Decimal`
 - [ ] Improved JSDoc for relation 1:1 & 1:n fields
 
 ##### Midterm
@@ -227,8 +227,9 @@ However some of the Prisma scalars do not have a natural standard representation
 | `DateTime` | `DateTime` | `dateTime`       | [DateTime](https://www.graphql-scalars.dev/docs/scalars/datetime)     |                                                                                                              |
 | `BigInt`   | `BigInt`   | `bigInt`         | [BigInt](https://www.graphql-scalars.dev/docs/scalars/big-int)        | [JavaScript BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt) |
 | `Bytes`    | `Bytes`    | `bytes`          | [Byte](https://www.graphql-scalars.dev/docs/scalars/byte/)            | [Node.js Buffer](https://nodejs.org/api/buffer.html#buffer_buffer)                                           |
+| `Decimal`  | `Decimal`  | `decimal`        | (internal)                                                            | Uses [Decimal.js](https://github.com/MikeMcl/decimal.js)                                                     |
 
-> **Note:** Not all Prisma scalar mappings are implemented yet: `Decimal`, `Unsupported`
+> **Note:** Not all Prisma scalar mappings are implemented yet: `Unsupported`
 
 > **Note:** BigInt is supported in Node.js since version [10.4.0](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt#browser_compatibility) however to support BigInt in `JSON.parse`/`JSON.stringify` you must use [`json-bigint-patch`](https://github.com/ardatan/json-bigint-patch) otherwise BigInt values will be serialized as strings.
 

package.json

@@ -92,6 +92,7 @@
   "dependencies": {
     "@prisma/generator-helper": "^2.27.0",
     "debug": "^4.3.2",
+    "decimal.js": "^10.3.1",
     "dindist": "^1.0.2",
     "expand-tilde": "^2.0.2",
     "fs-jetpack": "^4.1.0",

src/entrypoints/scalars.ts

@@ -1,6 +1,7 @@
 import { BigInt } from '../scalars/BigInt'
 import { Bytes } from '../scalars/Bytes'
 import { DateTime } from '../scalars/DateTime'
+import { Decimal } from '../scalars/Decimal'
 import { Json } from '../scalars/Json'
 
 /**
@@ -13,6 +14,8 @@ import { Json } from '../scalars/Json'
  * | `DateTime` | `DateTime` | `dateTime`       | [DateTime](https://www.graphql-scalars.dev/docs/scalars/datetime)     |                                                                                                              |
  * | `BigInt`   | `BigInt`   | `bigInt`         | [BigInt](https://www.graphql-scalars.dev/docs/scalars/big-int)        | [JavaScript BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt) |
  * | `Bytes`    | `Bytes`    | `bytes`          | [Byte](https://www.graphql-scalars.dev/docs/scalars/byte/)            | [Node.js Buffer](https://nodejs.org/api/buffer.html#buffer_buffer)                                           |
+ * | `Decimal` | `Decimal` | `decimal` | (internal) | Uses [Decimal.js](https://github.com/MikeMcl/decimal.js)
+ * |.
  *
  * @example
  *
@@ -76,9 +79,10 @@ const NexusPrismaScalars = {
   BigInt,
   Bytes,
   DateTime,
+  Decimal,
   Json,
 }
 
 export default NexusPrismaScalars
 
-export { BigInt, Bytes, DateTime, Json }
+export { BigInt, Bytes, DateTime, Decimal, Json }

src/generator/models/declaration.ts

@@ -306,7 +306,7 @@ export function fieldTypeToGraphQLType(
           return 'Bytes'
         }
         case 'Decimal': {
-          return StandardGraphQLScalarTypes.String
+          return 'Decimal'
         }
         default: {
           return allCasesHandled(typeName)

src/scalars/Decimal.ts

@@ -0,0 +1,62 @@
+import { asNexusMethod } from 'nexus'
+import * as DecimalJs from 'decimal.js'
+
+import { GraphQLScalarType, Kind } from 'graphql'
+
+/**
+ * A Nexus scalar type definition for arbitrary-precision Decimal type.
+ *
+ * Contributes a scalar to your GraphQL schema called `Decimal`.
+ *
+ * Contributes a `t` `[1]` helper method called `decimal`
+ *
+ * `[1]` A `t` helper method refers to a method on the argument given to a `definition` method. Helper methods
+ * here typically help you quickly create new fields.
+ *
+ * @example
+ *
+ *   import { makeSchema, objectType } from 'nexus'
+ *   import { Decimal } from 'nexus-prisma/scalars'
+ *
+ *   SomeObject = objectType({
+ *     name: 'SomeObject',
+ *     definition(t) {
+ *       t.decimal('someDecimalField')
+ *     },
+ *   })
+ *
+ *   makeSchema({
+ *     types: [Decimal, SomeObject],
+ *   })
+ *
+ */
+export const Decimal = asNexusMethod(
+  /**
+   * Copied from prisma-graphql-type-decimal.
+   *
+   * @see https://github.com/unlight/prisma-graphql-type-decimal
+   */
+  new GraphQLScalarType({
+    name: 'Decimal',
+    description: 'An arbitrary-precision Decimal type',
+    /**
+     * Value sent to the client
+     */
+    serialize(value: DecimalJs.Decimal) {
+      return value.toString()
+    },
+    /**
+     * Value from the client
+     */
+    parseValue(value: DecimalJs.Decimal.Value) {
+      return new DecimalJs.Decimal(value)
+    },
+    parseLiteral(ast) {
+      if (ast.kind === Kind.INT || ast.kind === Kind.FLOAT || ast.kind === Kind.STRING) {
+        return new DecimalJs.Decimal(ast.value)
+      }
+      return null
+    },
+  }),
+  'decimal'
+)

tests/e2e/__snapshots__/e2e.test.ts.snap

@@ -8,13 +8,15 @@ Object {
         "BigIntManually": null,
         "BytesManually": null,
         "DateTimeManually": null,
+        "DecimalManually": null,
         "JsonManually": null,
         "someBigIntField": "9007199254740991",
         "someBytesField": Object {
           "data": Array [],
           "type": "Buffer",
         },
         "someDateTimeField": "2021-05-10T20:42:46.609Z",
+        "someDecimalField": "24.454545",
         "someEnumA": "alpha",
         "someJsonField": Object {},
       },
@@ -46,14 +48,19 @@ A date-time string at UTC, such as 2007-12-03T10:15:30Z, compliant with the \`da
 \\"\\"\\"
 scalar DateTime
 
+\\"\\"\\"An arbitrary-precision Decimal type\\"\\"\\"
+scalar Decimal
+
 type Foo {
   BigIntManually: BigInt
   BytesManually: Bytes
   DateTimeManually: DateTime
+  DecimalManually: Decimal
   JsonManually: Json
   someBigIntField: BigInt!
   someBytesField: Bytes!
   someDateTimeField: DateTime!
+  someDecimalField: Decimal!
   someEnumA: SomeEnumA
   someJsonField: Json!
 }
@@ -98,6 +105,10 @@ declare global {
      * A date-time string at UTC, such as 2007-12-03T10:15:30Z, compliant with the \`date-time\` format outlined in section 5.6 of the RFC 3339 profile of the ISO 8601 standard for representation of dates and times using the Gregorian calendar.
      */
     dateTime<FieldName extends string>(fieldName: FieldName, opts?: core.CommonInputFieldConfig<TypeName, FieldName>): void // \\"DateTime\\";
+    /**
+     * An arbitrary-precision Decimal type
+     */
+    decimal<FieldName extends string>(fieldName: FieldName, opts?: core.CommonInputFieldConfig<TypeName, FieldName>): void // \\"Decimal\\";
     /**
      * The \`JSONObject\` scalar type represents JSON objects as specified by [ECMA-404](http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf).
      */
@@ -119,6 +130,10 @@ declare global {
      * A date-time string at UTC, such as 2007-12-03T10:15:30Z, compliant with the \`date-time\` format outlined in section 5.6 of the RFC 3339 profile of the ISO 8601 standard for representation of dates and times using the Gregorian calendar.
      */
     dateTime<FieldName extends string>(fieldName: FieldName, ...opts: core.ScalarOutSpread<TypeName, FieldName>): void // \\"DateTime\\";
+    /**
+     * An arbitrary-precision Decimal type
+     */
+    decimal<FieldName extends string>(fieldName: FieldName, ...opts: core.ScalarOutSpread<TypeName, FieldName>): void // \\"Decimal\\";
     /**
      * The \`JSONObject\` scalar type represents JSON objects as specified by [ECMA-404](http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf).
      */
@@ -147,6 +162,7 @@ export interface NexusGenScalars {
   BigInt: any
   Bytes: any
   DateTime: any
+  Decimal: any
   Json: any
 }
 
@@ -174,10 +190,12 @@ export interface NexusGenFieldTypes {
     BigIntManually: NexusGenScalars['BigInt'] | null; // BigInt
     BytesManually: NexusGenScalars['Bytes'] | null; // Bytes
     DateTimeManually: NexusGenScalars['DateTime'] | null; // DateTime
+    DecimalManually: NexusGenScalars['Decimal'] | null; // Decimal
     JsonManually: NexusGenScalars['Json'] | null; // Json
     someBigIntField: NexusGenScalars['BigInt']; // BigInt!
     someBytesField: NexusGenScalars['Bytes']; // Bytes!
     someDateTimeField: NexusGenScalars['DateTime']; // DateTime!
+    someDecimalField: NexusGenScalars['Decimal']; // Decimal!
     someEnumA: NexusGenEnums['SomeEnumA'] | null; // SomeEnumA
     someJsonField: NexusGenScalars['Json']; // Json!
   }
@@ -194,10 +212,12 @@ export interface NexusGenFieldTypeNames {
     BigIntManually: 'BigInt'
     BytesManually: 'Bytes'
     DateTimeManually: 'DateTime'
+    DecimalManually: 'Decimal'
     JsonManually: 'Json'
     someBigIntField: 'BigInt'
     someBytesField: 'Bytes'
     someDateTimeField: 'DateTime'
+    someDecimalField: 'Decimal'
     someEnumA: 'SomeEnumA'
     someJsonField: 'Json'
   }

tests/e2e/e2e.test.ts

@@ -120,6 +120,7 @@ it('When bundled custom scalars are used the project type checks and generates e
             id                String   @id
             someJsonField     Json
             someDateTimeField DateTime
+            someDecimalField  Decimal
             someBytesField    Bytes
             someBigIntField   BigInt
             someEnumA         SomeEnumA
@@ -143,7 +144,7 @@ it('When bundled custom scalars are used the project type checks and generates e
     {
       filePath: `prisma/seed.ts`,
       content: dedent/*ts*/ `
-        import { PrismaClient } from '@prisma/client'
+        import { PrismaClient, Prisma } from '@prisma/client'
 
         main()
 
@@ -155,6 +156,7 @@ it('When bundled custom scalars are used the project type checks and generates e
             data: {
               id: 'foo1',
               someDateTimeField: new Date("2021-05-10T20:42:46.609Z"),
+              someDecimalField: 24.454545,
               someBytesField: Buffer.from([]),
               someJsonField: {},
               someBigIntField: BigInt(9007199254740991),
@@ -214,11 +216,13 @@ it('When bundled custom scalars are used the project type checks and generates e
               t.json('JsonManually')
               t.dateTime('DateTimeManually')
               t.bytes('BytesManually')
+              t.decimal('DecimalManually')
               t.bigInt('BigIntManually')
               t.field(Foo.someBigIntField)
               t.field(Foo.someJsonField)
               t.field(Foo.someDateTimeField)
               t.field(Foo.someBytesField)
+              t.field(Foo.someDecimalField)
             },
           }),
         ]
@@ -380,11 +384,13 @@ it('When bundled custom scalars are used the project type checks and generates e
           JsonManually
           DateTimeManually
           BytesManually
+          DecimalManually
           BigIntManually
           someEnumA
           someJsonField
           someDateTimeField
           someBytesField
+          someDecimalField
           someBigIntField
         }
       }

tests/integration/json.test.ts

@@ -18,6 +18,7 @@ testIntegration({
       NexusPrismaScalars.Bytes,
       NexusPrismaScalars.BigInt,
       NexusPrismaScalars.DateTime,
+      NexusPrismaScalars.Decimal,
       NexusPrismaScalars.Json,
       objectType({
         name: Foo.$name,

tests/unit/customScalarsModule.test.ts

@@ -9,6 +9,7 @@ Array [
   "BigInt",
   "Bytes",
   "DateTime",
+  "Decimal",
   "Json",
   "default",
 ]
@@ -21,6 +22,7 @@ it('scalars can be accessed via a default import', () => {
       "BigInt",
       "Bytes",
       "DateTime",
+      "Decimal",
       "Json",
     ]
   `)

yarn.lock

@@ -2080,6 +2080,11 @@ decimal.js@^10.2.1:
   resolved "https://registry.yarnpkg.com/decimal.js/-/decimal.js-10.2.1.tgz#238ae7b0f0c793d3e3cea410108b35a2c01426a3"
   integrity sha512-KaL7+6Fw6i5A2XSnsbhm/6B+NuEA7TZ4vqxnd5tXz9sbKtrN9Srj8ab4vKVdK8YAqZO9P1kg45Y6YLoduPf+kw==
 
+decimal.js@^10.3.1:
+  version "10.3.1"
+  resolved "https://registry.yarnpkg.com/decimal.js/-/decimal.js-10.3.1.tgz#d8c3a444a9c6774ba60ca6ad7261c3a94fd5e783"
+  integrity sha512-V0pfhfr8suzyPGOx3nmq4aHqabehUZn6Ch9kyFpV79TGDTWFmHqUqXdabR7QHqxzrYolF4+tVmJhUG4OURg5dQ==
+
 decompress-response@^3.3.0:
   version "3.3.0"
   resolved "https://registry.yarnpkg.com/decompress-response/-/decompress-response-3.3.0.tgz#80a4dd323748384bfa248083622aedec982adff3"