feat: deno run --unstable-hmr (#20876)

This commit adds `--unstable-hmr` flag, that enabled Hot Module Replacement.

This flag works like `--watch` and accepts the same arguments. If
HMR is not possible the process will be restarted instead.

Currently HMR is only supported in `deno run` subcommand.

Upon HMR a `CustomEvent("hmr")` will be dispatched that contains
information which file was changed in its `details` property.

---------

Co-authored-by: Valentin Anger <syrupthinker@gryphno.de>
Co-authored-by: David Sherret <dsherret@gmail.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/cli/args/mod.rs b/cli/args/mod.rs
index ab8d6b503..96f4e9a74 100644
--- a/cli/args/mod.rs
+++ b/cli/args/mod.rs
@@ -1130,6 +1130,18 @@ impl CliOptions {
     &self.flags.ext
   }
 
+  pub fn has_hmr(&self) -> bool {
+    if let DenoSubcommand::Run(RunFlags {
+      watch: Some(WatchFlagsWithPaths { hmr, .. }),
+      ..
+    }) = &self.flags.subcommand
+    {
+      *hmr
+    } else {
+      false
+    }
+  }
+
   /// If the --inspect or --inspect-brk flags are used.
   pub fn is_inspecting(&self) -> bool {
     self.flags.inspect.is_some()