fix: add support for prisma ^2.20

Author: William Luke

package.json

@@ -42,13 +42,13 @@
     "url": "https://github.com/notiz-dev/prisma-dbml-generator/issues"
   },
   "dependencies": {
-    "@prisma/generator-helper": "^2.15.0"
+    "@prisma/generator-helper": "^2.20.0",
+    "@prisma/sdk": "^2.20.0"
   },
   "devDependencies": {
-    "@prisma/cli": "^2.15.0",
-    "@prisma/client": "^2.15.0",
-    "@prisma/sdk": "^2.15.0",
-    "@types/jest": "26.0.20",
+    "prisma": "^2.20.0",
+    "@prisma/client": "^2.20.0",
+    "@types/jest": "^26.0.20",
     "@types/node": "12.19.5",
     "jest": "26.6.3",
     "prettier": "2.2.1",

src/cli/dbml-generator.ts

@@ -1,14 +1,20 @@
 import { GeneratorOptions } from '@prisma/generator-helper';
-import { generateDBMLSchema } from '../generator/dbml';
+import { parseEnvValue } from '@prisma/sdk';
 import { promises } from 'fs';
 import { join } from 'path';
+import { generateDBMLSchema } from '../generator/dbml';
 
 const { mkdir, writeFile } = promises;
 
 export const defaultDBMLFileName = 'schema.dbml';
 
 export async function generate(options: GeneratorOptions) {
-  const outputDir = options.generator.output!;
+  const outputDir =
+    // This ensures previous version of prisma are still supported
+    typeof options.generator.output === 'string'
+      ? //@ts-ignore
+        (options.generator.output! as string)
+      : parseEnvValue(options.generator.output!);
   const dbmlFileName =
     options.generator.config.outputName || defaultDBMLFileName;
   const allowManyToMany =