From e320614159edca800e3366d7ceab5c5dc7014e4d Mon Sep 17 00:00:00 2001
From: Eric Crosson <ericcrosson@bitgo.com>
Date: Mon, 23 Dec 2024 15:00:06 -0600
Subject: [PATCH] feat(openapi-generator): suggest resolution for unknown codec
 types

The Problem
-----------

If you try to import a codec from `io-ts-types` like this:

```typescript
import { DateFromISOString} from 'io-ts-types/DateFromISOString';
```

you will see an error like this:

```
node_modules/@api-ts/openapi-generator/dist/src/codec.js:287
    if (init.type === 'Identifier' || init.type === 'MemberExpression') {
             ^

TypeError: Cannot read properties of null (reading 'type')
```

This is not a helpful error message, as it does not indicate

1. What went wrong?
2. What does the user need to do to fix it?

Additional Context
------------------

Since codecs from `io-ts-types` are frequently used,
@api-ts/openapi-generator ships with knowledge of `io-ts-types`
codecs[^1]. However, these defaults only match against the user's code
when the user imports from the top-level `io-ts-types` package, like
this:

```typescript
import { DateFromISOString} from 'io-ts-types';
```

This Change
-----------

This diff detects when @api-ts/openapi-generator encounters a codec
for which it cannot determine encode/decode types. This happens when a
codec is declared with `t.Type` instead of the io-ts combinators, which
happens in `io-ts-types` and in some third-party modules.

In this case, the generator will now print a message informing the
user what went wrong, and provides a suggestion on how the user should
resolve the issue:

> [ERROR] Could not determine encode/decode types for codec 'MyCustomCodec' in '~/workspace/node_modules/my-custom-types/lib/MyCustomType.d.ts'
> Consider defining a custom codec for this type.
>
> https://github.com/BitGo/api-ts/tree/master/packages/openapi-generator#4-defining-custom-codecs

Additionally, when the path defining the codec comes from `io-ts-types`,
the message is even more specific:

> [ERROR] Could not determine encode/decode types for codec 'DateFromISOString' in '~/workspace/node_modules/io-ts-types/lib/DateFromISOString.d.ts'
> It looks like this codec comes from io-ts-types. Try importing directly from io-ts-types instead:
>
> ```
> import { DateFromISOString } from 'io-ts-types';
> ```

Considerations
--------------

I was not able to easily write any tests for this functionality, since
our test harness does not currently handle failure cases and asserting
against given error messages.

[^1]: https://github.com/BitGo/api-ts/blob/b214578caa8272e8370025ae3ef6fd7bf45d514c/packages/openapi-generator/src/knownImports.ts#L334
---
 packages/openapi-generator/src/cli.ts | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/packages/openapi-generator/src/cli.ts b/packages/openapi-generator/src/cli.ts
index e7cc5a28..a1b64ab2 100644
--- a/packages/openapi-generator/src/cli.ts
+++ b/packages/openapi-generator/src/cli.ts
@@ -179,6 +179,33 @@ const app = command({
         }
         const [newSourceFile, init, comment] = initE.right;
 
+        if (init === null) {
+          console.log({ ref });
+          let errorMessage = `Could not determine encode/decode types for codec '${ref.name}' in '${ref.location}'`;
+          if (ref.location.includes('/node_modules/io-ts-types/')) {
+            errorMessage += `
+              It looks like this codec comes from io-ts-types. Try importing directly from io-ts-types instead:
+
+              \`\`\`
+              import { ${ref.name} } from 'io-ts-types';
+              \`\`\`
+            `;
+          } else {
+            errorMessage += `
+              Consider defining a custom codec for this type.
+
+              https://github.com/BitGo/api-ts/tree/master/packages/openapi-generator#4-defining-custom-codecs
+            `;
+          }
+          logError(
+            errorMessage
+              .split('\n')
+              .map((line) => line.trimStart())
+              .join('\n'),
+          );
+          process.exit(1);
+        }
+
         const codecE = parseCodecInitializer(project, newSourceFile, init);
         if (E.isLeft(codecE)) {
           logError(