fix: 🐛 use ts import transformer when transpileOnly:true

✅ Closes: #91

Author: kaisermann

Diff for: package-lock.json

@@ -30,7 +30,7 @@
     "test": "jest --no-cache",
     "test:watch": "jest --no-cache --watchAll",
     "lint": "eslint **/*.ts",
-    "format": "prettier --loglevel silent --write \"src/**/*.js\" && eslint --fix \"src/**/*.js\"",
+    "format": "prettier --loglevel silent --write \"src/**/*.ts\" && eslint --fix \"src/**/*.ts\"",
     "postinstall": "node -e \"console.log('\\u001b[36m\\u001b[1m[svelte-preprocess] Don\\'t forget to install the preprocessors packages that will be used: \\u001b[22m\\u001b[39m\\u001b[34mnode-sass/sass, stylus, less, postcss &  postcss-load-config, coffeescript, pug, etc...\\u001b[0m')\"",
     "version": "conventional-changelog -p angular -i CHANGELOG.md -s -r 0 && git add CHANGELOG.md",
     "tag": "git tag -a v$npm_package_version -m 'Release v$npm_package_version'",

Diff for: package.json

@@ -1,4 +1,4 @@
-import path from 'path'
+import path from 'path';
 import stylus from 'stylus';
 
 import { getIncludePaths } from '../utils';
@@ -28,7 +28,9 @@ const transformer: Transformer<Options.Stylus> = ({
         code: css,
         map: (style as any).sourcemap,
         // .map() necessary for windows compatibility
-        dependencies: style.deps(filename).map((filePath: string) => path.resolve(filePath)),
+        dependencies: style
+          .deps(filename)
+          .map((filePath: string) => path.resolve(filePath)),
       });
     });
   });

Diff for: src/transformers/stylus.ts

@@ -79,6 +79,10 @@ const importTransformer: ts.TransformerFactory<ts.SourceFile> = context => {
   return node => ts.visitNode(node, visit);
 };
 
+const TS_TRANSFORMERS = {
+  before: [importTransformer],
+};
+
 function compileFileFromMemory(
   compilerOptions: CompilerOptions,
   { filename, content }: { filename: string; content: string },
@@ -89,16 +93,18 @@ function compileFileFromMemory(
   const realHost = ts.createCompilerHost(compilerOptions, true);
   const dummyFileName = ts.sys.resolvePath(filename);
 
-  const isDummyFile = (fileName: string) => ts.sys.resolvePath(fileName) === dummyFileName
+  const isDummyFile = (fileName: string) =>
+    ts.sys.resolvePath(fileName) === dummyFileName;
 
   const host: ts.CompilerHost = {
     fileExists: fileName =>
       isDummyFile(fileName) || realHost.fileExists(fileName),
-    getCanonicalFileName: fileName => isDummyFile(fileName)
-      ? ts.sys.useCaseSensitiveFileNames
-        ? fileName
-        : fileName.toLowerCase()
-      : realHost.getCanonicalFileName(fileName),
+    getCanonicalFileName: fileName =>
+      isDummyFile(fileName)
+        ? ts.sys.useCaseSensitiveFileNames
+          ? fileName
+          : fileName.toLowerCase()
+        : realHost.getCanonicalFileName(fileName),
     getSourceFile: (
       fileName,
       languageVersion,
@@ -108,11 +114,11 @@ function compileFileFromMemory(
       isDummyFile(fileName)
         ? ts.createSourceFile(dummyFileName, code, languageVersion)
         : realHost.getSourceFile(
-          fileName,
-          languageVersion,
-          onError,
-          shouldCreateNewSourceFile,
-        ),
+            fileName,
+            languageVersion,
+            onError,
+            shouldCreateNewSourceFile,
+          ),
     readFile: fileName =>
       isDummyFile(fileName) ? content : realHost.readFile(fileName),
     writeFile: (fileName, data) => {
@@ -136,9 +142,13 @@ function compileFileFromMemory(
   };
 
   const program = ts.createProgram([dummyFileName], compilerOptions, host);
-  const emitResult = program.emit(undefined, undefined, undefined, undefined, {
-    before: [importTransformer],
-  });
+  const emitResult = program.emit(
+    undefined,
+    undefined,
+    undefined,
+    undefined,
+    TS_TRANSFORMERS,
+  );
 
   // collect diagnostics without svelte import errors
   const diagnostics = [
@@ -216,6 +226,7 @@ const transformer: Transformer<Options.Typescript> = ({
         fileName: filename,
         compilerOptions: compilerOptions,
         reportDiagnostics: options.reportDiagnostics !== false,
+        transformers: TS_TRANSFORMERS,
       },
     ));
   } else {

Diff for: src/transformers/typescript.ts

@@ -3,4 +3,3 @@ declare module 'coffeescript';
 declare module 'strip-indent';
 declare module 'postcss-load-config';
 declare module 'less';
-