fix(add): handle version tags like @latest in deno add for JSR packages (#32859)

## Summary

`deno add jsr:@std/cli@latest` panics with:
```
programming error: cannot use matches with a tag: latest
```

The version tag `latest` was passed through to
`deno_semver::VersionReq::matches()` which panics on tags. Fix by
detecting tags via `version_req.tag()` in the add command's version
selection (`find_package_and_select_version_for_req`) and resolving
to the latest version via `latest_version()` instead.

This matches the pattern used elsewhere in the codebase (LSP,
cache_deps,
outdated) where `tag()` is checked before calling `matches()`.

Closes #31298

Author: bartlomieju

cli/tools/pm/mod.rs

@@ -765,46 +765,64 @@ async fn find_package_and_select_version_for_req(
     };
     let prefixed_name = format!("{}:{}", T::SPECIFIER_PREFIX, req.name);
     let help_if_found_in_fallback = S::HELP;
-    let nv = match main_resolver.req_to_nv(req).await {
-      Ok(Some(nv)) => nv,
-      Ok(None) => {
-        if fallback_resolver
-          .req_to_nv(req)
-          .await
-          .ok()
-          .flatten()
-          .is_some()
-        {
-          // it's in the other registry
-          return Ok(PackageAndVersion::NotFound {
-            package: prefixed_name,
-            help: Some(help_if_found_in_fallback),
-            package_req: req.clone(),
-          });
-        }
-
-        return Ok(PackageAndVersion::NotFound {
-          package: prefixed_name,
-          help: None,
-          package_req: req.clone(),
-        });
+    // JSR has no dist-tags, so a tag can't go through req_to_nv
+    // (VersionReq::matches panics on a tag). "@latest" is conventionally
+    // understood as "the newest version", so resolve it to the latest
+    // published version; reject any other tag rather than silently treating
+    // it as latest. npm resolves dist-tags natively via its registry, so this
+    // only applies to JSR.
+    let maybe_nv = if matches!(
+      &add_package_req.value,
+      AddRmPackageReqValue::Jsr(_)
+    ) && let Some(tag) = req.version_req.tag()
+    {
+      if tag != "latest" {
+        bail!(
+          "{} does not support the tag '{tag}'. JSR has no dist-tags; use '@latest' or a version requirement instead.",
+          prefixed_name,
+        );
       }
-      Err(err) => {
-        if req.version_req.version_text() == "*"
-          && let Some(pre_release_version) =
-            main_resolver.latest_version(&req.name).await
-        {
-          return Ok(PackageAndVersion::NotFound {
-            package: prefixed_name,
-            package_req: req.clone(),
-            help: Some(NotFoundHelp::PreReleaseVersion(
-              pre_release_version.clone(),
-            )),
-          });
+      main_resolver
+        .latest_version(&req.name)
+        .await
+        .map(|version| PackageNv {
+          name: req.name.clone(),
+          version,
+        })
+    } else {
+      match main_resolver.req_to_nv(req).await {
+        Ok(maybe_nv) => maybe_nv,
+        Err(err) => {
+          if req.version_req.version_text() == "*"
+            && let Some(pre_release_version) =
+              main_resolver.latest_version(&req.name).await
+          {
+            return Ok(PackageAndVersion::NotFound {
+              package: prefixed_name,
+              package_req: req.clone(),
+              help: Some(NotFoundHelp::PreReleaseVersion(
+                pre_release_version.clone(),
+              )),
+            });
+          }
+          return Err(err);
         }
-        return Err(err);
       }
     };
+    let Some(nv) = maybe_nv else {
+      // Not in the primary registry; point at the other one if it's there.
+      let help = fallback_resolver
+        .req_to_nv(req)
+        .await
+        .ok()
+        .flatten()
+        .map(|_| help_if_found_in_fallback);
+      return Ok(PackageAndVersion::NotFound {
+        package: prefixed_name,
+        help,
+        package_req: req.clone(),
+      });
+    };
     let range_symbol = if req.version_req.version_text().starts_with('~') {
       "~"
     } else if save_exact

tests/specs/add/dist_tag/__test__.jsonc

@@ -1,9 +1,30 @@
 {
   "tempDir": true,
-  "steps": [
-    {
-      "args": "add npm:ajv@latest",
-      "output": "add.out"
+  "tests": {
+    "npm_latest": {
+      "steps": [
+        {
+          "args": "add npm:ajv@latest",
+          "output": "add.out"
+        }
+      ]
+    },
+    "jsr_latest": {
+      "steps": [
+        {
+          "args": "add jsr:@denotest/add@latest",
+          "output": "add_jsr.out"
+        }
+      ]
+    },
+    "jsr_unsupported_tag": {
+      "steps": [
+        {
+          "args": "add jsr:@denotest/add@beta",
+          "output": "add_jsr_unsupported_tag.out",
+          "exitCode": 1
+        }
+      ]
     }
-  ]
+  }
 }

tests/specs/add/dist_tag/add_jsr.out

@@ -0,0 +1,2 @@
+Add jsr:@denotest/add@[WILDCARD]
+[WILDCARD]

tests/specs/add/dist_tag/add_jsr_unsupported_tag.out

@@ -0,0 +1 @@
+error: jsr:@denotest/add does not support the tag 'beta'. JSR has no dist-tags; use '@latest' or a version requirement instead.