preserve imports from stale files (#90)

This PR adds support for automatically preserving `import` statements in
`functions.ts` and `api.ts` files

## Why
This was required because if a user had a setup in which they were using
functions from files other than `api.ts` and had `@save` annotation on
those functions, re-running the codegen (introspect with overwrite set
to `true`) would preserve the function, but would lose its import
statement. This meant that the user would have to re-write their import
statements again, which a really bad experience.

## Note
`import` statements are always preserved and organized. They don't need
a `@save` annotation.

## Review
Since this is a relatively large PR, it'll be easier to review it per
commit

Author: m-Bilal

changelog.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Add support for `@save` in `api.ts` ([#89](https://github.com/hasura/ndc-open-api-lambda/pull/89))
+- Add support for preserving imports from stale files ([#90](https://github.com/hasura/ndc-open-api-lambda/pull/90))
 
 ## [[1.5.2](https://github.com/hasura/ndc-open-api-lambda/releases/tag/v1.5.2)] 2025-03-25
 

docs/documentation.md

@@ -76,6 +76,8 @@ When re-introspecting the connector, user changes in `functions.ts` or `api.ts`
 
 This will ensure that the statements marked with `@save` are not overwritten and the saved statements will be added if missing in the newly generated `functions.ts` or the `apt.ts` file
 
+> **NOTE:** `import` statements are always preserved and orgranized for both files, they don't need the `@save` annotation
+
 Example
 
 ```javascript

src/app/parser/typescript/cleanup.ts

@@ -19,16 +19,12 @@ export function fixImports(generatedCodeList: types.GeneratedCode[]) {
     project.createSourceFile(
       generatedCode.filePath,
       generatedCode.fileContent,
-      {
-        overwrite: true,
-      },
+      { overwrite: true },
     );
   }
 
   try {
     for (const sourceFile of project.getSourceFiles()) {
-      sourceFile.fixMissingImports().organizeImports();
-
       // find the source file in the generated code file list
       let curSourceFile =
         generatedCodeList.filter(
@@ -41,12 +37,18 @@ export function fixImports(generatedCodeList: types.GeneratedCode[]) {
             path.basename(sourceFile.getFilePath()),
         )[0];
 
-      if (curSourceFile) {
+      if (curSourceFile) { // if the current file is either functions.ts or api.ts, fix imports and organize them
+        sourceFile.fixMissingImports().organizeImports();
         curSourceFile!.fileContent = sourceFile.getFullText();
       } else {
-        logger.error(
-          `Error while fixing imports: Unable to find the source file for ${sourceFile.getFilePath()}\n\nSkipping import fixing and cleanup for this file`,
-        );
+        if (
+          path.basename(sourceFile.getFilePath()) === "functions.ts" ||
+          path.basename(sourceFile.getFilePath()) === "api.ts"
+        ) { // we only want to show this error if we're unable to find functions.ts or api.ts
+          logger.error(
+            `Error while fixing imports: Unable to find the source file for ${sourceFile.getFilePath()}\n\nSkipping import fixing and cleanup for this file`,
+          );
+        }
       }
     }
   } catch (error) {

src/app/parser/typescript/index.ts

@@ -26,5 +26,8 @@ export function preserveUserChanges(
   morph.preserveSavedVariables(staleSourceFile, freshSourceFile);
   morph.preserveSavedFunctions(staleSourceFile, freshSourceFile);
 
+  // imports don't need @save annotation, they are always preserved and organized
+  morph.preserveImportDeclarations(staleSourceFile, freshSourceFile);
+
   return freshSourceFile.getFullText();
 }

src/app/parser/typescript/morph.test.ts

@@ -137,6 +137,40 @@ describe("morph::user-defined-types", async () => {
   }
 });
 
+const importDeclarationsTests: TestCase[] = [
+  {
+    name: "Preserve Imports",
+    directory: "./test-data/morph-tests/imports/",
+  }
+];
+
+describe("morph::import-declarations", async () => {
+  for (const testCase of importDeclarationsTests) {
+    before(function () {
+      setupTest(testCase);
+    });
+
+    it(testCase.name, async () => {
+      morph.preserveImportDeclarations(
+        testCase.staleSourceFile!,
+        testCase.freshSourceFile!,
+      );
+
+      const gotStr = await prettier.format(
+        testCase.freshSourceFile?.getFullText()!,
+        {
+          parser: "typescript",
+        },
+      );
+
+      assert.equal(testCase.mergedFileContents, gotStr);
+
+      // uncomment to update merged golden file
+      // fs.writeFileSync(path.resolve(testCase.directory, "merged.ts"), gotStr);
+    });
+  }
+});
+
 function setupTest(testCase: TestCase) {
   testCase.directory = path.resolve(__dirname, testCase.directory);
   const staleProject = new ts.Project();

src/app/parser/typescript/morph.ts

@@ -65,6 +65,29 @@ export function preserveSavedClasses(
   preserveNode(staleSourceClasses, freshSourceClasses, freshTsSourceFile);
 }
 
+export function preserveImportDeclarations(
+  staleTsSourceFile: tsMorph.SourceFile,
+  freshTsSourceFile: tsMorph.SourceFile,
+) {
+  const staleSourceImports = walk.getAllImportDeclarationsMap(staleTsSourceFile);
+  const freshSourceImports = walk.getAllImportDeclarationsMap(freshTsSourceFile);
+
+  staleSourceImports.forEach((staleNode, staleNodeName) => {
+    const freshNode = freshSourceImports.get(staleNodeName);
+
+    if (freshNode) {
+      // this import statement already exists in the fresh source file
+      // replace it with the stale import statement
+      freshNode.replaceWithText(staleNode.getText());
+    } else {
+      // this import statement does not exist in the fresh source file
+      // add it to the fresh source
+      freshTsSourceFile.insertStatements(0, staleNode.getText());
+    }
+  })
+}
+
+
 /**
  * this function preservers nodes that are marked with `@save` annotation in the stale source file
  * if a saved node is missing in the fresh source file, it will be copied to it

src/app/parser/typescript/test-data/morph-tests/imports/a.ts

@@ -0,0 +1,3 @@
+export function helloWorld() {
+    return "hello world";
+}

src/app/parser/typescript/test-data/morph-tests/imports/fresh.ts

@@ -0,0 +1,5 @@
+import * as a from "./a";
+import * as tsMorph from "ts-morph";
+import { exit } from "process";
+import { SemVer } from "semver";
+

src/app/parser/typescript/test-data/morph-tests/imports/merged.ts

@@ -0,0 +1,13 @@
+import * as fs from "fs";
+import * as path from "path";
+import { helloWorld } from "./a";
+import {
+  SourceFile,
+  SourceFileEmitOptions,
+  NamespaceImport,
+  NamedImports,
+  NamedExports,
+  ModuleDeclaration,
+} from "ts-morph";
+import * as process from "process";
+import { SemVer } from "semver";

src/app/parser/typescript/test-data/morph-tests/imports/stale.ts

@@ -0,0 +1,14 @@
+import { helloWorld } from "./a";
+import {
+  SourceFile,
+  SourceFileEmitOptions,
+  NamespaceImport,
+  NamedImports,
+  NamedExports,
+  ModuleDeclaration,
+} from "ts-morph";
+import * as process from "process";
+import * as path from "path";
+import * as fs from "fs";
+
+export function hello() {}