feat: save dep with tag if install with tag (#408)

Follow npm/rfcs#547

bin/install.js

@@ -164,6 +164,7 @@ for (const name of argv._) {
     version: p.fetchSpec || p.rawSpec,
     type: p.type,
     alias: aliasPackageName,
+    arg: p,
   });
 }
 
@@ -460,7 +461,6 @@ function getIgnoreScripts() {
 }
 
 async function updateDependencies(root, pkgs, propName, saveExact, remoteNames) {
-  const savePrefix = saveExact ? '' : getVersionSavePrefix();
   const pkgFile = path.join(root, 'package.json');
   const pkg = await utils.readJSON(pkgFile);
   const deps = pkg[propName] = pkg[propName] || {};
@@ -476,7 +476,16 @@ async function updateDependencies(root, pkgs, propName, saveExact, remoteNames)
     } else {
       const pkgDir = LOCAL_TYPES.includes(item.type) ? item.version : path.join(root, 'node_modules', item.name);
       const itemPkg = await utils.readJSON(path.join(pkgDir, 'package.json'));
-      deps[itemPkg.name] = `${savePrefix}${itemPkg.version}`;
+
+      let saveSpec;
+      // If install with `cnpm i foo`, the type is tag but rawSpec is empty string
+      if (item.arg.type === 'tag' && item.arg.rawSpec) {
+        saveSpec = item.arg.rawSpec;
+      } else {
+        const savePrefix = saveExact ? '' : getVersionSavePrefix();
+        saveSpec = `${savePrefix}${itemPkg.version}`;
+      }
+      deps[itemPkg.name] = saveSpec;
     }
   }
   // sort pkg[propName]

test/installSaveDeps.test.js

@@ -245,5 +245,21 @@ if (process.platform !== 'win32') {
           done();
         });
     });
+
+    it('install with dist-tag should update dependencies with tag', done => {
+      coffee.fork(helper.npminstall, [
+        'pedding@latest',
+      ], {
+        cwd: tmp,
+      })
+        .expect('code', 0)
+        .end(err => {
+          assert(!err, err && err.message);
+          const deps = JSON.parse(fs.readFileSync(path.join(tmp, 'package.json'))).dependencies;
+          assert(deps);
+          assert(deps.pedding === 'latest');
+          done();
+        });
+    });
   });
 }