From e1cef6019b9a601eaba7d491dc181082fa23a183 Mon Sep 17 00:00:00 2001
From: Piotr Kaminski <piotr@ideanest.com>
Date: Wed, 16 Sep 2020 16:20:55 -0700
Subject: [PATCH] Split out V2 and V1 result handling, and tighten up types.

---
 snowpack/src/build/build-pipeline.ts               | 14 ++++++++++----
 snowpack/src/config.ts                             |  2 +-
 snowpack/src/types/snowpack.ts                     |  9 ++++++---
 .../transform-sourcemap/custom-transform-plugin.js |  2 +-
 4 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/snowpack/src/build/build-pipeline.ts b/snowpack/src/build/build-pipeline.ts
index 54fcafd2c6..859d08ad3e 100644
--- a/snowpack/src/build/build-pipeline.ts
+++ b/snowpack/src/build/build-pipeline.ts
@@ -1,7 +1,7 @@
 import path from 'path';
 import {validatePluginLoadResult} from '../config';
 import {logger} from '../logger';
-import {SnowpackBuildMap, SnowpackConfig, SnowpackPlugin} from '../types/snowpack';
+import {SnowpackBuildMap, SnowpackConfig, SnowpackPlugin, PluginTransformResult} from '../types/snowpack';
 import {getExt, readFile, replaceExt} from '../util';
 import {SourceMapConsumer, SourceMapGenerator, RawSourceMap} from 'source-map';
 
@@ -156,11 +156,13 @@ async function runPipelineTransformStep(
         });
         logger.debug(`✔ transform() success [${debugPath}]`, {name: step.name});
         if (typeof result === 'string' || Buffer.isBuffer(result)) {
+          // V2 API, simple string variant
           output[destExt].code = result;
           output[destExt].map = undefined;
-        } else if (result && typeof result === 'object' && (result as {result: string}).result) {
-          output[destExt].code = (result as {result: string}).result;
-          let map = (result as {map: string | RawSourceMap}).map;
+        } else if (result && typeof result === 'object' && (result as PluginTransformResult).contents) {
+          // V2 API, structured result variant
+          output[destExt].code = (result as PluginTransformResult).contents;
+          const map = (result as PluginTransformResult).map;
           let outputMap: string | undefined = undefined;
           if (map && sourceMaps) {  // if source maps disabled, don’t return any
             if (output[destExt].map) {
@@ -170,6 +172,10 @@ async function runPipelineTransformStep(
             }
           }
           output[destExt].map = outputMap;
+        } else if (result && typeof result === 'object' && (result as unknown as {result: string}).result) {
+          // V1 API, deprecated
+          output[destExt].code = (result as unknown as {result: string}).result;
+          output[destExt].map = undefined;
         }
       }
     } catch (err) {
diff --git a/snowpack/src/config.ts b/snowpack/src/config.ts
index ad4cd9e76a..178cf1fe99 100644
--- a/snowpack/src/config.ts
+++ b/snowpack/src/config.ts
@@ -730,7 +730,7 @@ function validatePlugin(plugin: SnowpackPlugin) {
 
 export function validatePluginLoadResult(
   plugin: SnowpackPlugin,
-  result: PluginLoadResult | void | undefined | null,
+  result: PluginLoadResult | string | void | undefined | null,
 ) {
   const pluginName = plugin.name;
   if (!result) {
diff --git a/snowpack/src/types/snowpack.ts b/snowpack/src/types/snowpack.ts
index 547e8e5b0e..0f270d5e5d 100644
--- a/snowpack/src/types/snowpack.ts
+++ b/snowpack/src/types/snowpack.ts
@@ -1,6 +1,7 @@
 import type HttpProxy from 'http-proxy';
 import type * as http from 'http';
 import type {InstallOptions} from 'esinstall';
+import type {RawSourceMap} from 'source-map';
 
 export type DeepPartial<T> = {
   [P in keyof T]?: T[P] extends Array<infer U>
@@ -51,7 +52,9 @@ export interface PluginRunOptions {
 }
 
 /** map of extensions -> code (e.g. { ".js": "[code]", ".css": "[code]" }) */
-export type PluginLoadResult = string | SnowpackBuildMap;
+export type PluginLoadResult = SnowpackBuildMap;
+
+export type PluginTransformResult = {contents: string, map: string | RawSourceMap};
 
 export interface PluginOptimizeOptions {
   buildDirectory: string;
@@ -73,9 +76,9 @@ export interface SnowpackPlugin {
     output: string[];
   };
   /** load a file that matches resolve.input */
-  load?(options: PluginLoadOptions): Promise<PluginLoadResult | null | undefined | void>;
+  load?(options: PluginLoadOptions): Promise<PluginLoadResult | string | null | undefined | void>;
   /** transform a file that matches resolve.input */
-  transform?(options: PluginTransformOptions): Promise<string | null | undefined | void>;
+  transform?(options: PluginTransformOptions): Promise<PluginTransformResult | string | null | undefined | void>;
   /** runs a command, unrelated to file building (e.g. TypeScript, ESLint) */
   run?(options: PluginRunOptions): Promise<unknown>;
   /** optimize the entire built application */
diff --git a/test/build/transform-sourcemap/custom-transform-plugin.js b/test/build/transform-sourcemap/custom-transform-plugin.js
index a51dd603e0..39360dfe07 100644
--- a/test/build/transform-sourcemap/custom-transform-plugin.js
+++ b/test/build/transform-sourcemap/custom-transform-plugin.js
@@ -7,7 +7,7 @@ module.exports = function () {
       ms.appendLeft(contents.indexOf('console.log'), `console.log('transformed');\n`);
       const map = ms.generateMap({source: id, hires: false, includeContent: true});
       return {
-        result: ms.toString(),
+        contents: ms.toString(),
         // Try returning both object and string map formats.
         map: fileExt === '.js' ? map : map.toString()
       }