fix(add): create deno.json when running deno add jsr:<pkg> (#26275)

Fixes https://github.com/denoland/deno/issues/26119.

Originally I wanted to put them in package.json if there's no deno.json,
but on second thought it makes more sense to just create a deno.json

cli/tools/registry/pm.rs

@@ -400,14 +400,17 @@ impl std::fmt::Display for AddCommandName {
 
 fn load_configs(
   flags: &Arc<Flags>,
+  has_jsr_specifiers: impl FnOnce() -> bool,
 ) -> Result<(CliFactory, Option<NpmConfig>, Option<DenoConfig>), AnyError> {
   let cli_factory = CliFactory::from_flags(flags.clone());
   let options = cli_factory.cli_options()?;
   let npm_config = NpmConfig::from_options(options)?;
   let (cli_factory, deno_config) = match DenoConfig::from_options(options)? {
     Some(config) => (cli_factory, Some(config)),
-    None if npm_config.is_some() => (cli_factory, None),
+    None if npm_config.is_some() && !has_jsr_specifiers() => {
-    None => {
+      (cli_factory, None)
+    }
+    _ => {
       let factory = create_deno_json(flags, options)?;
       let options = factory.cli_options()?.clone();
       (
@@ -427,7 +430,9 @@ pub async fn add(
   add_flags: AddFlags,
   cmd_name: AddCommandName,
 ) -> Result<(), AnyError> {
-  let (cli_factory, npm_config, deno_config) = load_configs(&flags)?;
+  let (cli_factory, npm_config, deno_config) = load_configs(&flags, || {
+    add_flags.packages.iter().any(|s| s.starts_with("jsr:"))
+  })?;
   let mut npm_config = ConfigUpdater::maybe_new(npm_config).await?;
   let mut deno_config = ConfigUpdater::maybe_new(deno_config).await?;
 
@@ -764,7 +769,7 @@ pub async fn remove(
   flags: Arc<Flags>,
   remove_flags: RemoveFlags,
 ) -> Result<(), AnyError> {
-  let (_, npm_config, deno_config) = load_configs(&flags)?;
+  let (_, npm_config, deno_config) = load_configs(&flags, || false)?;
 
   let mut configs = [
     ConfigUpdater::maybe_new(npm_config).await?,

tests/specs/add/jsr_prefers_deno_json/__test__.jsonc

@@ -0,0 +1,16 @@
+{
+  "tempDir": true,
+  "steps": [
+    {
+      "args": "add jsr:@denotest/add",
+      "output": "add.out"
+    },
+    {
+      "args": [
+        "eval",
+        "console.log(Deno.readTextFileSync('./deno.json').trim())"
+      ],
+      "output": "deno.json.out"
+    }
+  ]
+}

tests/specs/add/jsr_prefers_deno_json/add.out

@@ -0,0 +1,3 @@
+Created deno.json configuration file.
+Add jsr:@denotest/add@1.0.0
+Download [WILDCARD]

tests/specs/add/jsr_prefers_deno_json/deno.json.out

@@ -0,0 +1,5 @@
+{
+  "imports": {
+    "@denotest/add": "jsr:@denotest/add@^1.0.0"
+  }
+}

tests/specs/add/jsr_prefers_deno_json/package.json

@@ -0,0 +1 @@
+{}