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https://github.com/denoland/deno_graph

The module graph logic for Deno CLI
https://github.com/denoland/deno_graph

deno rust typescript webassembly

Last synced: 27 days ago
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The module graph logic for Deno CLI

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README 

        
# deno_graph



[![JSR](https://jsr.io/badges/@deno/graph)](https://jsr.io/@deno/graph)

[![Build Status - Cirrus][]][Build status] [![Twitter handle][]][Twitter badge]

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The module graph/dependency logic for the Deno CLI.



This repository is a Rust crate which provides the foundational code to be able

to build a module graph, following the Deno CLI's module resolution logic. It

also provides a web assembly interface to the built code, making it possible to

leverage the logic outside of the Deno CLI from JavaScript/TypeScript.



## Rust usage



### `ModuleGraph::new(...)`



`ModuleGraph::new(GraphKind::All)` creates a new module graph. From there, you

can use the `.build(...).await` method to add roots. The `build` method requires

the root module specifiers/URLs for the graph and an implementation of the

`source::Loader` trait. It also optionally takes implementation of the

`source::Resolver` trait. It will load and parse the root module and recursively

all of its dependencies, returning asynchronously a resulting `ModuleGraph`.



### `source::Loader` trait



Implementing this trait requires the `load()` method and optionally the

`get_cache_into()` method. The `load()` method returns a future with the

requested module specifier and the resulting load response. This allows the

module graph to deal with redirections, error conditions, and local and remote

content.



The `get_cache_info()` is the API for exposing additional meta data about a

module specifier as it resides in the cache so it can be part of a module graphs

information. When the graph is built, the method will be called with each

resolved module in the graph to see if the additional information is available.



### `source::Resolver` trait



This trait "replaces" the default resolution logic of the module graph. It is

intended to allow concepts like import maps and alternative resolution logic to

"plug" into the module graph.



It has two methods, `resolve` and `resolve_types`, which both have default

implementations. `resolve` takes the string specifier from the source and the

referring specifier and is expected to return a result with the resolved

specifier.



`resolve_types` takes a specifier and is expected to return a result with an

optional module specifier and optional source range of the types that should be

used. For example, if you are trying represent the `"typings"` field from a

`package.json` file, when you receive the request on `resolve_types` for the

main module of the package, you would respond with the absolute specifier to the

types along with a range that indicates the file URL to the `package.json` and

the range where it was specified. Including the range is useful to allow errors

produced from the graph to indicate "where" the dependency came from.



### `source::MemoryLoader` struct



`MemoryLoader` is a structure that implements the `source::Loader` trait and is

designed so that a cache of modules can be stored in memory to be parsed and

retrieved when building a module graph. This is useful for testing purposes or

in situations where the module contents is already available and _dynamically_

loading them is not practical or desirable.



A minimal example would look like this:



```rust

use deno_graph::ModuleSpecifier;

use deno_graph::ModuleGraph;

use deno_graph::GraphKind;

use deno_graph::source::MemoryLoader;

use deno_graph::source::Source;

use futures::executor::block_on;



fn main() {

  let mut loader = MemoryLoader::new(

    vec![

      (

        "file:///test.ts",

        Source::Module {

          specifier: "file:///test.ts",

          maybe_headers: None,

          content: "import * as a from \"./a.ts\";"

        }

      ),

      (

        "file:///a.ts",

        Source::Module {

          specifier: "file:///a.ts",

          maybe_headers: None,

          content: "export const a = \"a\";",

        }

      ),

    ],

    Vec::new(),

  );

  let roots = vec![ModuleSpecifier::parse("file:///test.ts").unwrap()];

  let future = async move {

    let mut graph = ModuleGraph::new(GraphKind::All);

    graph.build(roots, &loader, Default::default()).await;

    println!("{:#?}", graph);

  };

  block_on(future)

}

```



## Usage from Deno CLI or Deploy



See [js/README.md](js/README.md).



## Building Web Assembly



The build script (`_build.ts`) requires the Deno CLI to be installed and

available in the path. If it is, the following command should _just work_:



```

> deno task build

```



## Versioning Strategy



This crate does not follow semver so make sure to pin it to a patch version.

Instead a versioning strategy that optimizes for more efficient maintenance is

used:



- Does [deno_doc](https://github.com/denoland/deno_doc) and

  [eszip](https://github.com/denoland/eszip) still compile in the

  [Deno](https://github.com/denoland/deno) repo?

  - If yes, it's a patch release.

  - If no, it's a minor release.



### Contributing



We appreciate your help!



To contribute, please read our

[contributing instructions](https://deno.land/manual/contributing).



This repository includes `.devcontainer` metadata which will allow a development

container to be built which has all the development pre-requisites available to

make contribution easier.



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