Add package manager parsers (npm, pip, go, cargo)

src/depcheck/parsers/npm.py

@@ -0,0 +1,60 @@
+"""NPM package.json parser."""
+
+import json
+from pathlib import Path
+
+from depcheck.models import Dependency, PackageManager
+from depcheck.parsers import Parser
+from depcheck.utils import parse_version_string
+
+
+class NpmParser(Parser):
+    """Parser for npm package.json files."""
+
+    package_manager = PackageManager.NPM
+
+    def supports_file(self, file_path: Path) -> bool:
+        return file_path.name == "package.json"
+
+    def get_file_patterns(self) -> list[str]:
+        return ["package.json"]
+
+    def parse(self, file_path: Path) -> list[Dependency]:
+        dependencies: list[Dependency] = []
+
+        try:
+            content = file_path.read_text()
+            data = json.loads(content)
+        except (json.JSONDecodeError, OSError):
+            return dependencies
+
+        sections = [
+            ("dependencies", "dependencies"),
+            ("devDependencies", "devDependencies"),
+            ("optionalDependencies", "optionalDependencies"),
+        ]
+
+        for section_key, category in sections:
+            section = data.get(section_key, {})
+            if not isinstance(section, dict):
+                continue
+
+            for name, version_info in section.items():
+                if isinstance(version_info, dict):
+                    version = version_info.get("version", "")
+                else:
+                    version = str(version_info)
+
+                version = parse_version_string(version)
+                if version:
+                    dependencies.append(
+                        Dependency(
+                            name=name,
+                            current_version=version,
+                            package_manager=self.package_manager,
+                            category=category,
+                            source_file=str(file_path),
+                        )
+                    )
+
+        return dependencies