fix: create Program on-demand when file exists (#126)

In this test, the `node_modules/d3-drag` path is linked to `../../d3-drag` (which is a local package, not from node_modules).
This setup mimics a monorepo, where dependencies often point to local packages.
The local `d3-drag` package contains an `index.d.ts` module.
This test fails with `Unexpected token` error, since no `Program` is found for the `d3-drag/index.d.ts` module.

.gitignore

@@ -2,5 +2,5 @@
 .nyc_output
 coverage
 dist
-node_modules
+/node_modules
 .build

src/index.ts

@@ -3,7 +3,7 @@ import { PluginImpl, SourceDescription } from "rollup";
 import * as ts from "typescript";
 
 import { NamespaceFixer } from "./NamespaceFixer";
-import { createPrograms, dts, formatHost } from "./program";
+import { createProgram, createPrograms, dts, formatHost } from "./program";
 import { reorderStatements } from "./reorder";
 import { Transformer } from "./Transformer";
 
@@ -34,17 +34,9 @@ const plugin: PluginImpl<Options> = (options = {}) => {
   function getModule(fileName: string) {
     let source: ts.SourceFile | undefined;
     let program: ts.Program | undefined;
-    if (programs.length) {
-      // Rollup doesn't tell you the entry point of each module in the bundle,
-      // so we need to ask every TypeScript program for the given filename.
-      for (program of programs) {
-        source = program.getSourceFile(fileName);
-        if (source) break;
-      }
-    }
     // Create any `ts.SourceFile` objects on-demand for ".d.ts" modules,
     // but only when there are zero ".ts" entry points.
-    else if (fileName.endsWith(dts)) {
+    if (!programs.length && fileName.endsWith(dts)) {
       const code = ts.sys.readFile(fileName, "utf8");
       if (code)
         source = ts.createSourceFile(
@@ -53,6 +45,14 @@ const plugin: PluginImpl<Options> = (options = {}) => {
           ts.ScriptTarget.Latest,
           true, // setParentNodes
         );
+    } else {
+      // Rollup doesn't tell you the entry point of each module in the bundle,
+      // so we need to ask every TypeScript program for the given filename.
+      program = programs.find((p) => (source = p.getSourceFile(fileName)));
+      if (!program && ts.sys.fileExists(fileName)) {
+        programs.push((program = createProgram(fileName, compilerOptions)));
+        source = program.getSourceFile(fileName);
+      }
     }
     return { source, program };
   }

src/program.ts

@@ -62,6 +62,15 @@ function getCompilerOptions(
   };
 }
 
+export function createProgram(fileName: string, overrideOptions: ts.CompilerOptions) {
+  const { dtsFiles, compilerOptions } = getCompilerOptions(fileName, overrideOptions)
+  return ts.createProgram(
+    [fileName].concat(Array.from(dtsFiles)),
+    compilerOptions,
+    ts.createCompilerHost(compilerOptions, true)
+  );
+}
+
 export function createPrograms(input: Array<string>, overrideOptions: ts.CompilerOptions) {
   const programs = [];
   let inputs: Array<string> = [];

tests/d3-drag/index.d.ts

@@ -0,0 +1,5 @@
+/**
+ * Container element type usable for mouse/touch functions
+ */
+type DragContainerElement = HTMLElement | SVGSVGElement | SVGGElement;
+export { DragContainerElement };

tests/d3-drag/package.json

@@ -0,0 +1 @@
+{"name": "d3-drag"}

tests/testcases/externals-link/expected.d.ts

@@ -0,0 +1,5 @@
+/**
+ * Container element type usable for mouse/touch functions
+ */
+type DragContainerElement = HTMLElement | SVGSVGElement | SVGGElement;
+export { DragContainerElement };

tests/testcases/externals-link/index.ts

@@ -0,0 +1 @@
+export { DragContainerElement } from "d3-drag";

tests/testcases/externals-link/meta.json

@@ -0,0 +1,8 @@
+{
+  "options": {
+    "respectExternal": true
+  },
+  "rollupOptions": {
+    "external": []
+  }
+}