Validate user input from init command

src/poetry/console/commands/init.py

@@ -13,9 +13,11 @@
 from cleo.helpers import option
 from packaging.utils import canonicalize_name
 from tomlkit import inline_table
+from tomlkit import parse
 
 from poetry.console.commands.command import Command
 from poetry.console.commands.env_command import EnvCommand
+from poetry.factory import Factory
 from poetry.utils.dependency_specification import RequirementsParser
 from poetry.utils.env.python import Python
 
@@ -265,6 +267,14 @@ def _init_pyproject(
 
             return 1
 
+        # Validate fields before creating pyproject.toml file. If any validations fail, throw an error.
+        # Convert TOML string to a TOMLDocument (a dict-like object) for validation.
+        pyproject_dict = parse(pyproject.data.as_string())
+        validation_results = self._validate(pyproject_dict)
+        if validation_results.get("errors"):
+            self.line_error(f"<error>Validation failed: {validation_results}</error>")
+            return 1
+
         pyproject.save()
 
         if create_layout:
@@ -533,3 +543,13 @@ def _get_pool(self) -> RepositoryPool:
             self._pool.add_repository(PyPiRepository(pool_size=pool_size))
 
         return self._pool
+
+    @staticmethod
+    def _validate(pyproject_data: dict[str, Any]) -> dict[str, Any]:
+        """
+        Validates the given pyproject data and returns the validation results.
+        """
+        # Instantiate a new Factory to avoid relying on shared/global state,
+        # which can cause unexpected behavior in other parts of the codebase or test suite.
+        factory = Factory()
+        return factory.validate(pyproject_data)

tests/console/commands/test_init.py

@@ -7,6 +7,7 @@
 
 from pathlib import Path
 from typing import TYPE_CHECKING
+from typing import Any
 
 import pytest
 
@@ -1143,3 +1144,78 @@ def test_get_pool(mocker: MockerFixture, source_dir: Path) -> None:
     assert isinstance(command, InitCommand)
     pool = command._get_pool()
     assert pool.repositories
+
+
+def build_pyproject_data(
+    project_name: str, description: str = "A project"
+) -> dict[str, Any]:
+    return {
+        "project": {
+            "name": project_name,
+            "version": "0.1.0",
+            "description": description,
+            "authors": [{"name": "Author Name", "email": "author@example.com"}],
+            "readme": "README.md",
+            "requires-python": ">=3.13",
+            "dependencies": [],
+        },
+        "tool": {},
+        "build-system": {
+            "requires": ["poetry-core>=2.0.0,<3.0.0"],
+            "build-backend": "poetry.core.masonry.api",
+        },
+    }
+
+
+@pytest.mark.parametrize(
+    "valid_project_name",
+    [
+        "newproject",
+        "new_project",
+        "new-project",
+        "new.project",
+        "newproject123",
+    ],
+)
+def test_valid_project_name(valid_project_name: str) -> None:
+    pyproject_data = build_pyproject_data(valid_project_name)
+    result = InitCommand._validate(pyproject_data)
+    assert result["errors"] == []
+
+
+@pytest.mark.parametrize(
+    "invalid_project_name, reason",
+    [
+        ("new+project", "plus sign"),
+        ("new/project", "slash"),
+        ("new@project", "at sign"),
+        ("new project", "space"),
+        ("", "empty string"),
+        (" newproject", "leading space"),
+        ("newproject ", "trailing space"),
+        ("new#project", "hash (#)"),
+        ("new%project", "percent (%)"),
+        ("new*project", "asterisk (*)"),
+        ("new(project)", "parentheses"),
+        ("-newproject", "leading hyphen"),
+        ("newproject-", "trailing hyphen"),
+        (".newproject", "leading dot"),
+        ("newproject.", "trailing dot"),
+        (
+            "_newproject",
+            "leading underscore (PEP 621 allows, stricter validators may reject)",
+        ),
+        (
+            "newproject_",
+            "trailing underscore (PEP 621 allows, stricter validators may reject)",
+        ),
+        ("1newproject!", "starts with digit, ends with exclamation"),
+        (".", "just dot"),
+    ],
+)
+def test_invalid_project_name(invalid_project_name: str, reason: str) -> None:
+    pyproject_data = build_pyproject_data(invalid_project_name)
+    result = InitCommand._validate(pyproject_data)
+
+    assert "errors" in result, f"Expected error for: {reason}"
+    assert any("project.name must match pattern" in err for err in result["errors"])