Read multiple files with Promise.all

Developers: Plugin & API
1

Hi, guys. I’m working on a plugin and I’m using the following code to read the content of a list of files:

const fileContents: string[] = await Promise.all(
   listFiles.map((file) => this.app.vault.cachedRead(file))
);

My problem is that this code returns an array with the content of the files, but I can’t figure out how to program a script that returns the contents of the files along with the name of the file the content is associated with. I can’t figure out how to do that with Promises. If anyone has any idea, I highly appreciate it.

Thanks
JD

2 
const fileContents: [path:string, content:string][] = await Promise.all(
   listFiles.map(async (file) => [file.path, await this.app.vault.cachedRead(file)])
);
for (const [path, content] of fileContents) {...}
3

Hi, aidenix. I tried to return a tuple before, but I always get the following error (this is the error I get with your code):

main.ts:73:9 - error TS2322: Type 'string[][]' is not assignable to type '[path: string, content: string][]'.
  Type 'string[]' is not assignable to type '[path: string, content: string]'.
    Target requires 2 element(s) but source may have fewer.

73   const fileContents: [path:string, content:string][] = await Promise.all(

Maybe I need to create a loop with Promises for each file? But I never worked with Promises before so I’m not sure how to do that.

Thanks in advance
JD

4

I think I’ve got it. I’ve created this loop and it works. Let me know if you see any potential bugs. Thanks again for your time.

		let listContents: [string, string][] = [];
		await listFiles.forEach(async (file) => {
			let content = await this.app.vault.cachedRead(file);
			listContents.push([file.name, content]);
		});
5

append as const should work, I didn’t notice the type issue because I wrote the code without IDE at that moment :joy:

const fileContents: [path:string, content:string][] = await Promise.all(
   listFiles.map(async (file) => [file.path, await this.app.vault.cachedRead(file)] as const)
);
for (const [path, content] of fileContents) {...}
6

Hi, aidenix. Unfortunately, I’m still getting an error. Now it says that the const values can’t be assigned to the mutable value (I removed the labels in the tuple but I get the same error).

main.ts:100:9 - error TS2322: Type '(readonly [string, string])[]' is not assignable to type '[string, string][]'.
  The type 'readonly [string, string]' is 'readonly' and cannot be assigned to the mutable type '[string, string]'.

100   const fileContents: [string, string][] = await Promise.all(

The loop I showed you before works, I’m just not sure if there is any possible bug in there.

Thanks
JD

7

you can do that loop of course, it’s just that the map will be more straightforward, the following code should stop the complaint from typescript

const fileContents = await Promise.all(
  listFiles.map(
    async (file) => [file.path, await app.vault.cachedRead(file)] as const,
  ),
);