build: allow disabling snapshots for dev (#20048)

Closes #19399 (running without snapshots at all was suggested as an
alternative solution).

Adds a `__runtime_js_sources` pseudo-private feature to load extension
JS sources at runtime for faster development, instead of building and
loading snapshots or embedding sources in the binary. Will only work in
a development environment obviously.

Try running `cargo test --features __runtime_js_sources
integration::node_unit_tests::os_test`. Then break some behaviour in
`ext/node/polyfills/os.ts` e.g. make `function cpus() {}` return an
empty array, and run it again. Fix and then run again. No more build
time in between.

1 files changed, 5 insertions, 0 deletions

diff --git a/cli/Cargo.toml b/cli/Cargo.toml
index 5ee0bd22d..c1779c102 100644
--- a/cli/Cargo.toml
+++ b/cli/Cargo.toml
@@ -26,6 +26,11 @@ name = "lsp_bench_standalone"
 harness = false
 path = "./bench/lsp_bench_standalone.rs"
 
+[features]
+# A dev feature to disable creations and loading of snapshots in favor of
+# loading JS sources at runtime.
+__runtime_js_sources = ["deno_runtime/__runtime_js_sources"]
+
 [build-dependencies]
 deno_runtime = { workspace = true, features = ["snapshot_from_snapshot", "include_js_files_for_snapshotting"] }
 deno_core = { workspace = true, features = ["include_js_files_for_snapshotting"] }