Add jscodeshift transform for v2->v3 migration

[dminkovsky]

I began migrating v2 to v3 today and decided to write a jscodeshift transform for some of the rote elements of this migration that do not need to be done by hand. Not sure if this belongs in the repo, but thought I would share it and perhaps others will expand? So far it does this:

-import {useApolloClient} from '@apollo/react-hooks';
-import gql from 'graphql-tag';
-import {Observable} from 'apollo-link';
+import { Observable, gql, useApolloClient } from "@apollo/client";

Anything else in this migration that can be dependably automated?

Thank you.

PS. You can play with this over at https://astexplorer.net:

[apollo-cla]

@dminkovsky: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Apollo Contributor License Agreement here: https://contribute.apollographql.com/

[benjamn]

This is a really great idea! Of course I'm biased because I've been involved with jscodeshift for a number of years, as the author of https://www.npmjs.com/package/recast. I will give some thought to other possible transforms that might simplify the migration story.

[dminkovsky]

Haha I noticed that after I saw that you added a tag to this issue yesterday. Thanks for recast! Really beats using sed. Wouldn't want to do something like this any other way.

[MichaelDeBoey]

@dminkovsky @benjamn Any idea when we can expect this one?
Would be really nice to be able to use this.

[hwillson]

Thanks for working on this @dminkovsky and @jcreighton! This is a great start, and we can definitely add more to this over time. I've listed a few small formatting nit's, but I do think we should also mention this in the migration guide somewhere. Maybe add a new level 3 section under ## Installation, that mentions we have a codemod to help with the AC2 -> AC3 transition, along with a super quick synopsis of what the codemod will take care of (and of course, how to call it). Thanks for working on this!

[dminkovsky]

Awesome to see this rounded out, thanks a lot @jcreighton. I gave myself a hard time limit to work on this when I wrote my original version, and I'm sorry I couldn't finish this. I think this will help a lot of people do the migration with confidence. It's been quite smooth for me. Definitely makes sense to mention it prominently at the migration guide—jscodeshift is awesome.

PS. Feel free to squash my two commits into one if you guys economize on commits. Would be nice to have at least one though :)

[bnjmnt4n]

Hey, I was working on a similar tool yesterday prior to seeing this PR and sent PR #6721 instead. Left some feedback on the approach taken here as suggested by @benjamn. I believe this utility would be a lot more useful if a lot more of the import mappings were added (such as from react-apollo, apollo-boost, etc.). Here's the list of mappings that I made (based on the Apollo migration docs and some internal imports from my codebase):

apollo-client/src/utilities/codemods/modifyImportsApollo3.ts

Lines 40 to 158 in 4248e92

	// Import mappings obtained from
	// https://www.apollographql.com/docs/react/migrating/apollo-client-3-migration/#updating-imports.
	// Note: order of execution is important.
	addImportMapping({ from: "@apollo/react-hooks", to: "@apollo/client", imports: "*" });
	addImportMapping({
	from: "@apollo/react-components",
	to: "@apollo/client/react/components",
	imports: "*",
	});
	addImportMapping({ from: "@apollo/react-hoc", to: "@apollo/client/react/ssr", imports: "*" });
	addImportMapping({ from: "@apollo/react-testing", to: "@apollo/client/testing", imports: "*" });
	addImportMapping({
	from: "react-apollo",
	to: "@apollo/client",
	imports: ["ApolloProvider", "MutationFunction", "useQuery", "useLazyQuery", "useMutation"],
	});
	addImportMapping({
	from: "apollo-boost",
	to: "@apollo/client",
	imports: [
	"ApolloClient",
	"HttpLink",
	"InMemoryCache",
	"NormalizedCacheObject",
	"Resolvers",
	"defaultDataIdFromObject",
	"gql",
	],
	});
	addImportMapping({
	from: "apollo-client",
	to: "@apollo/client",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-cache",
	to: "@apollo/client/cache",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-cache-inmemory",
	to: "@apollo/client/cache",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link",
	to: "@apollo/client/utilities",
	imports: ["getOperationName"],
	});
	addImportMapping({
	from: "apollo-link",
	to: "@apollo/client",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link-http",
	to: "@apollo/client",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link-http-common",
	to: "@apollo/client",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link-batch",
	to: "@apollo/client/link/batch",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link-batch-http",
	to: "@apollo/client/link/batch-http",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link-context",
	to: "@apollo/client/link/context",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link-error",
	to: "@apollo/client/link/error",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link-retry",
	to: "@apollo/client/link/retry",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-link-ws",
	to: "@apollo/client/link/ws",
	imports: "*",
	});
	addImportMapping({
	from: "apollo-utilities",
	to: "@apollo/client/utilities",
	imports: "*",
	});

.

[jcreighton]

Thank you @bnjmnt4n & @henryqdineen! I've updated this codemod with your suggestions!

[benjamn]

Some nitty/gritty final recommendations—I think we're getting very close!

[benjamn]

LGTM! @jcreighton I'll leave it to you to merge (with a merge commit, not squash or rebase) whenever you're ready.