warn if special chars in exported refs

conans/model/recipe_ref.py

@@ -3,6 +3,7 @@
 import re
 from functools import total_ordering
 
+from conan.api.output import ConanOutput
 from conans.errors import ConanException
 from conans.model.version import Version
 from conans.util.dates import timestamp_to_str
@@ -124,7 +125,7 @@ def validate_ref(self):
         if self_str != self_str.lower():
             raise ConanException(f"Conan packages names '{self_str}' must be all lowercase")
         if len(self_str) > 200:
-            raise ConanException(f"Package reference too long >250 {self_str}")
+            raise ConanException(f"Package reference too long >200 {self_str}")
         validation_pattern = re.compile(r"^[a-z0-9_][a-z0-9_+.-]{1,100}$")
         if validation_pattern.match(self.name) is None:
             raise ConanException(f"Invalid package name '{self.name}'")
@@ -135,6 +136,16 @@ def validate_ref(self):
         if self.channel and validation_pattern.match(self.channel) is None:
             raise ConanException(f"Invalid package channel '{self.channel}'")
 
+        # Warn if they use .+- in the name/user/channel, as it can be problematic for generators
+        pattern = re.compile(r'[.+-]')
+        if pattern.search(self.name):
+            ConanOutput().warning(f"Name containing special chars is discouraged '{self.name}'")
+        if self.user and pattern.search(self.user):
+            ConanOutput().warning(f"User containing special chars is discouraged '{self.user}'")
+        if self.channel and pattern.search(self.channel):
+            ConanOutput().warning(f"Channel containing special chars is discouraged "
+                                  f"'{self.channel}'")
+
     def matches(self, pattern, is_consumer):
         negate = False
         if pattern.startswith("!"):

conans/test/integration/command/export/export_test.py

@@ -517,6 +517,17 @@ def test_export_invalid_refs():
     assert "ERROR: Invalid package channel 'channel%'" in c.out
 
 
+def test_warn_special_chars_refs():
+    c = TestClient()
+    c.save({"conanfile.py": GenConanfile()})
+    c.run("export . --name=pkg.name --version=0.1")
+    assert "WARN: Name containing special chars is discouraged 'pkg.name'" in c.out
+    c.run("export . --name=name --version=0.1 --user=user+some")
+    assert "WARN: User containing special chars is discouraged 'user+some'" in c.out
+    c.run("export . --name=pkg.name --version=0.1 --user=user --channel=channel-some")
+    assert "WARN: Channel containing special chars is discouraged 'channel-some'" in c.out
+
+
 def test_export_json():
     c = TestClient()
     c.save({"conanfile.py": GenConanfile()})