feat(unstable): Workspaces support (#20410)

This commit adds unstable workspace support. This is extremely
bare-bones and
minimal first-pass at this.

With this change `deno.json` supports specifying `workspaces` key, that
accepts a list of subdirectories. Each workspace can have its own import
map. It's required to specify a `"name"` and `"version"` properties in the
configuration file for the workspace:

```jsonc
// deno.json
{
  "workspaces": [
     "a",
     "b"
  },
  "imports": {
    "express": "npm:express@5"
   }
}
```
``` jsonc
// a/deno.json
{
  "name": "a",
  "version": "1.0.2",
  "imports": {
    "kleur": "npm:kleur"
  }
}
```
```jsonc
// b/deno.json
{
  "name": "b",
  "version": "0.51.0",
  "imports": {
    "chalk": "npm:chalk"
  }
}
```

`--unstable-workspaces` flag is required to use this feature:
```
$ deno run --unstable-workspaces mod.ts
```

---------

Co-authored-by: David Sherret <dsherret@gmail.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/cli/args/flags.rs b/cli/args/flags.rs
index 235743bda..6d1e41a19 100644
--- a/cli/args/flags.rs
+++ b/cli/args/flags.rs
@@ -431,6 +431,7 @@ pub struct Flags {
   pub unstable: bool,
   pub unstable_bare_node_builtins: bool,
   pub unstable_byonm: bool,
+  pub unstable_workspaces: bool,
   pub unstable_features: Vec<String>,
   pub unsafely_ignore_certificate_errors: Option<Vec<String>>,
   pub v8_flags: Vec<String>,
@@ -871,6 +872,7 @@ pub fn flags_from_vec(args: Vec<String>) -> clap::error::Result<Flags> {
   flags.unstable_bare_node_builtins =
     matches.get_flag("unstable-bare-node-builtins");
   flags.unstable_byonm = matches.get_flag("unstable-byonm");
+  flags.unstable_workspaces = matches.get_flag("unstable-workspaces");
 
   if matches.get_flag("quiet") {
     flags.log_level = Some(Level::Error);
@@ -984,6 +986,15 @@ fn clap_root() -> Command {
         .value_parser(FalseyValueParser::new())
         .action(ArgAction::SetTrue)
         .global(true),
+    )
+    .arg(
+      Arg::new("unstable-workspaces")
+        .long("unstable-workspaces")
+        .help("Enable unstable 'workspaces' feature")
+        .env("DENO_UNSTABLE_WORKSPACES")
+        .value_parser(FalseyValueParser::new())
+        .action(ArgAction::SetTrue)
+        .global(true),
     );
 
   for (flag_name, help, _) in crate::UNSTABLE_GRANULAR_FLAGS {