fix(add/install): default to "latest" tag for npm packages in `deno add npm:pkg` (#25858)

Fixes #25813.

I initially tried doing this in `deno_semver`, where it's a cleaner
change, but that caused breakage in deno in places where we don't expect
a tag (see https://github.com/denoland/deno/issues/25857).

This does not fix wildcard requirements failing to choose pre-release
versions. That's a little more involved and I'll do a separate PR.

6 files changed, 37 insertions, 2 deletions

diff --git a/cli/tools/registry/pm.rs b/cli/tools/registry/pm.rs
index 05785ec74..c92710f46 100644
--- a/cli/tools/registry/pm.rs
+++ b/cli/tools/registry/pm.rs
@@ -5,6 +5,7 @@ mod cache_deps;
 pub use cache_deps::cache_top_level_deps;
 use deno_semver::jsr::JsrPackageReqReference;
 use deno_semver::npm::NpmPackageReqReference;
+use deno_semver::VersionReq;
 
 use std::borrow::Cow;
 use std::path::PathBuf;
@@ -717,7 +718,18 @@ impl AddPackageReq {
       Prefix::Npm => {
         let req_ref =
           NpmPackageReqReference::from_str(&format!("npm:{}", entry_text))?;
-        let package_req = req_ref.into_inner().req;
+        let mut package_req = req_ref.into_inner().req;
+        // deno_semver defaults to a version req of `*` if none is specified
+        // we want to default to `latest` instead
+        if package_req.version_req == *deno_semver::WILDCARD_VERSION_REQ
+          && package_req.version_req.version_text() == "*"
+          && !entry_text.contains("@*")
+        {
+          package_req.version_req = VersionReq::from_raw_text_and_inner(
+            "latest".into(),
+            deno_semver::RangeSetOrTag::Tag("latest".into()),
+          );
+        }
         Ok(Ok(AddPackageReq {
           alias: maybe_alias.unwrap_or_else(|| package_req.name.to_string()),
           value: AddPackageReqValue::Npm(package_req),
@@ -888,7 +900,9 @@ mod test {
       AddPackageReq::parse("@alias/pkg@npm:foo").unwrap().unwrap(),
       AddPackageReq {
         alias: "@alias/pkg".to_string(),
-        value: AddPackageReqValue::Npm(PackageReq::from_str("foo").unwrap())
+        value: AddPackageReqValue::Npm(
+          PackageReq::from_str("foo@latest").unwrap()
+        )
       }
     );
     assert_eq!(
diff --git a/tests/registry/npm/@denotest/unstable/1.0.0-beta.1/index.js b/tests/registry/npm/@denotest/unstable/1.0.0-beta.1/index.js
new file mode 100644
index 000000000..ba330abd5
--- /dev/null
+++ b/tests/registry/npm/@denotest/unstable/1.0.0-beta.1/index.js
@@ -0,0 +1,3 @@
+export function sayHello() { 
+  console.log("Hello") 
+}
\ No newline at end of file
diff --git a/tests/registry/npm/@denotest/unstable/1.0.0-beta.1/package.json b/tests/registry/npm/@denotest/unstable/1.0.0-beta.1/package.json
new file mode 100644
index 000000000..69f2a57cd
--- /dev/null
+++ b/tests/registry/npm/@denotest/unstable/1.0.0-beta.1/package.json
@@ -0,0 +1,5 @@
+{
+  "name": "@denotest/unstable",
+  "type": "module",
+  "version": "1.0.0-beta.1"
+}
\ No newline at end of file
diff --git a/tests/specs/add/only_unstable_versions/__test__.jsonc b/tests/specs/add/only_unstable_versions/__test__.jsonc
new file mode 100644
index 000000000..d05628b6f
--- /dev/null
+++ b/tests/specs/add/only_unstable_versions/__test__.jsonc
@@ -0,0 +1,9 @@
+{
+  "tempDir": true,
+  "steps": [
+    {
+      "args": "add npm:@denotest/unstable",
+      "output": "add.out"
+    }
+  ]
+}
diff --git a/tests/specs/add/only_unstable_versions/add.out b/tests/specs/add/only_unstable_versions/add.out
new file mode 100644
index 000000000..48462b8be
--- /dev/null
+++ b/tests/specs/add/only_unstable_versions/add.out
@@ -0,0 +1,3 @@
+Add npm:@denotest/unstable@1.0.0-beta.1
+Download http://localhost:4260/@denotest/unstable
+Download http://localhost:4260/@denotest/unstable/1.0.0-beta.1.tgz
diff --git a/tests/specs/add/only_unstable_versions/deno.json b/tests/specs/add/only_unstable_versions/deno.json
new file mode 100644
index 000000000..0967ef424
--- /dev/null
+++ b/tests/specs/add/only_unstable_versions/deno.json
@@ -0,0 +1 @@
+{}