deno_graph
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The module graph logic for Deno CLI
deno_graph
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
create_graph()
create_graph()
is the main way of interfacing with the crate. It requires the
root module specifiers/URLs for the graph and an implementation of the
source::Loader
trait. It also optionally takes implementations of the
source::Resolver
and source::Locker
traits. 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::Locker
trait
This trait allows the module graph to perform sub-resource integrity checks on a module graph.
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:
use deno_graph::create_graph;
use deno_graph::ModuleSpecifier;
use deno_graph::source::MemoryLoader;
use futures::executor::block_on;
fn main() {
let mut loader = MemoryLoader::new(
vec![
("file:///test.ts", Ok(("file:///test.ts", None, "import * as a from \"./a.ts\";"))),
("file:///a.ts", Ok(("file:///a.ts", None, "export const a = \"a\";"))),
]
);
let roots = vec![ModuleSpecifier::parse("file:///test.ts").unwrap()];
let future = async move {
let graph = create_graph(roots, &mut loader, None, None).await;
println!("{}", graph);
};
block_on()
}
Other core concepts
ModuleSpecifier
type alias
Currently part of the the deno_core
crate. deno_graph
explicitly doesn't
depend on deno_core
or any part of the Deno CLI. It exports the type alias
publicably for re-use by other crates.
MediaType
enum
Currently part of the deno_cli
crate, this enum represents the various media
types that the Deno CLI can resolve and handle. Since deno_graph
doesn't rely
upon any part of the Deno CLI, it was necessary to implement this in this crate,
and the implementation here will eventually replace the implementation in
deno_cli
.
Usage from Deno CLI or Deploy
This repository includes a compiled version of the Rust crate as Web Assembly
and exposes an interface which is availble via the mod.ts
in this repository
and can be imported like:
import * as denoGraph from "https://deno.land/x/deno_graph@{VERSION}/mod.ts";
Where {VERSION}
should be substituted with the specific version you want to
use.
createGraph()
The createGraph()
function allows a module graph to be built asynchronously.
It requires a root specifier or any array of root specifiers to be passed, which
will serve as the roots of the module graph.
There are several options that can be passed the function in the optional
options
argument:
-
load
- a callback function that takes a URL string and a flag indicating if the dependency was required dynamically (e.g.const m = await import("mod.ts")
) and resolves with aLoadResponse
. By default aload()
function that will attempt to load local modules viaDeno.readFile()
and load remote modules viafetch()
. -
cacheInfo
- a callback function that takes a URL string and returns aCacheInfo
object. In the Deno CLI, theDENO_DIR
cache info is passed back using this interface. If the function is not provided, the information is not present in the module graph. -
resolve
- a callback function that takes a string and a referring URL string and returns a fully qualified URL string. In the Deno CLI, import maps provide this callback functionality of potentially resolving modules differently than the default resolution. -
resolveTypes
- a callback function that takes a URL string and returns the types dependency for the specifier, along with optionally the source of the types dependency. This only gets called in situations where the module is potentially untyped (e.g. JavaScript, JSX) and no other type dependency was detected. This is intended to enrich the module graph with external types that are resolved in some other fashion, like from apackage.json
or via detecting an@types
typings package is available. -
check
- a callback function that takes a URL string and anUint8Array
of the byte content of a module to validate if that module sub resource integrity is valid. The callback should returntrue
if it is, otherwisefalse
. If the callback is not provided, all checks will pass. -
getChecksum
- a callback function that takes anUint8Array
of the byte content of a module in order to be able to return a string which represent a checksum of the provided data. If the callback is not provided, the checksum will be generated in line with the way the Deno CLI generates the checksum.
Replicating the Deno CLI
deno_graph
is essentially a refactor of the module graph and related code as a
stand alone crate which also targets Web Assembly and provides a
JavaScript/TypeScript interface. This permits users of the package to be able to
replicate the deno info
command in Deno CLI within the runtime environment
without requiring a Deno
namespace API.
The module graph has two methods which provide the output of deno info
. The
method toString()
provides the text output from deno info
and toJSON()
provides the JSON object structure from deno info --json
.
ℹ️ currently, there is no runtime access to the
DENO_DIR
/Deno cache, and there is no default implementation of the API when creating a module graph, therefore cache information is missing from the output. An implementation of something that read theDENO_DIR
cache is possible from CLI, but not currently implemented.
To replicate deno info https://deno.land/x/std/testing/asserts.ts
, you would
want to do something like this:
import { createGraph } from "https://deno.land/x/deno_graph@{VERSION}/mod.ts";
const graph = await createGraph("https://deno.land/x/std/testing/asserts.ts");
console.log(graph.toString());
This would output to stdout and would respect the NO_COLOR
/Deno.noColor
setting. If colors are allowed, the string will include the ANSI color escape
sequences, otherwise they will be omitted. This behavior can be explicitly
overridden by passing true
to always remove ANSI colors or false
to force
them.
To replicate deno info --json https://deno.land/x/std/testing/asserts.ts
, you
would want to do something like this:
import { createGraph } from "https://deno.land/x/deno_graph@{VERSION}/mod.ts";
const graph = await createGraph("https://deno.land/x/std/testing/asserts.ts");
console.log(JSON.stringify(graph, undefined, " "));
This would output to stdout the JSON structure of the module graph.
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
Contributing
We appreciate your help!
To contribute, please read our contributing instructions.
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.