chore: adds follow imports example

Author: Michael Dougall

example-transformers/follow-imports/import.ts

@@ -0,0 +1,3 @@
+export const hello = 'world';
+
+export default 'hello';

example-transformers/follow-imports/source.ts

@@ -0,0 +1,3 @@
+import { hello } from './import';
+
+console.log(hello);

example-transformers/follow-imports/transformed/import.js

@@ -0,0 +1,2 @@
+export const hello = 'world';
+export default 'hello';

example-transformers/follow-imports/transformed/source.js

@@ -0,0 +1,2 @@
+import { hello } from './import';
+console.log(hello);

example-transformers/follow-imports/transformer.ts

@@ -0,0 +1,33 @@
+import * as ts from 'typescript';
+
+const transformerProgram = (program: ts.Program) => {
+  const transformerFactory: ts.TransformerFactory<ts.SourceFile> = context => {
+    return sourceFile => {
+      const visitor = (node: ts.Node): ts.Node => {
+        if (
+          ts.isImportDeclaration(node) &&
+          ts.isStringLiteral(node.moduleSpecifier) &&
+          ts.isNamedImports(node.importClause.namedBindings)
+        ) {
+          const moduleImportName = node.moduleSpecifier.text;
+          const { resolvedFileName } = (sourceFile as any).resolvedModules.get(moduleImportName);
+          const moduleSourceFile = program.getSourceFile(resolvedFileName);
+
+          (moduleSourceFile as any).symbol.exports.forEach((_, key) => {
+            console.log(`found export ${key}`);
+          });
+
+          return node;
+        }
+
+        return ts.visitEachChild(node, visitor, context);
+      };
+
+      return ts.visitNode(sourceFile, visitor);
+    };
+  };
+
+  return transformerFactory;
+};
+
+export default transformerProgram;

example-transformers/follow-imports/tsconfig.json

@@ -0,0 +1,8 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "outDir": "transformed",
+    "plugins": [{ "transform": "./transformer.ts" }]
+  },
+  "files": ["source.ts"]
+}

translations/en/transformer-handbook.md

@@ -123,7 +123,7 @@ In its AST representation looks like this:
 ```
 
 For a more detailed look check out the [AST yourself](https://ts-ast-viewer.com/#code/GYVwdgxgLglg9mABACwKYBt10QCgJSIDeAUImYhAgM5zqoB0WA5jgOQDucATugCat4A3MQC+QA)!
-You can see also see the code that you can use the generate the same AST in the bottom left panel,
+You can also see the code can be used to generate the same AST in the bottom left panel,
 and the selected node metadata in the right panel.
 Super useful!
 
@@ -1100,8 +1100,40 @@ return ts.visitEachChild(node, visitor, context);
 
 #### Following module imports
 
+Following imports is possible -
+however I'm not currently sure it's supported in user land.
+This also may or may not break when type checking is turned off.
+
 > **TODO** - Is this possible in a robust way?
 
+```ts
+if (
+  ts.isImportDeclaration(node) &&
+  ts.isStringLiteral(node.moduleSpecifier) &&
+  ts.isNamedImports(node.importClause.namedBindings)
+) {
+  const moduleImportName = node.moduleSpecifier.text;
+  const { resolvedFileName } = sourceFile.resolvedModules.get(moduleImportName);
+  const moduleSourceFile = program.getSourceFile(resolvedFileName);
+
+  moduleSourceFile.symbol.exports.forEach((_, key) => {
+    console.log(`found export ${key}`);
+  });
+
+  return node;
+}
+```
+
+Which will log this to the console:
+
+```
+found export hello
+found export default
+```
+
+> **Tip** - You can s
+> ee the source for this at [/example-transformers/follow-imports](/example-transformers/follow-imports)
+
 #### Transforming jsx
 
 Typescript can also transform [JSX](https://reactjs.org/docs/introducing-jsx.html) -