community[major], core[patch], langchain[patch], experimental[patch]: Create langchain-community (#14463)

Moved the following modules to new package langchain-community in a backwards compatible fashion:

```
mv langchain/langchain/adapters community/langchain_community
mv langchain/langchain/callbacks community/langchain_community/callbacks
mv langchain/langchain/chat_loaders community/langchain_community
mv langchain/langchain/chat_models community/langchain_community
mv langchain/langchain/document_loaders community/langchain_community
mv langchain/langchain/docstore community/langchain_community
mv langchain/langchain/document_transformers community/langchain_community
mv langchain/langchain/embeddings community/langchain_community
mv langchain/langchain/graphs community/langchain_community
mv langchain/langchain/llms community/langchain_community
mv langchain/langchain/memory/chat_message_histories community/langchain_community
mv langchain/langchain/retrievers community/langchain_community
mv langchain/langchain/storage community/langchain_community
mv langchain/langchain/tools community/langchain_community
mv langchain/langchain/utilities community/langchain_community
mv langchain/langchain/vectorstores community/langchain_community
mv langchain/langchain/agents/agent_toolkits community/langchain_community
mv langchain/langchain/cache.py community/langchain_community
mv langchain/langchain/adapters community/langchain_community
mv langchain/langchain/callbacks community/langchain_community/callbacks
mv langchain/langchain/chat_loaders community/langchain_community
mv langchain/langchain/chat_models community/langchain_community
mv langchain/langchain/document_loaders community/langchain_community
mv langchain/langchain/docstore community/langchain_community
mv langchain/langchain/document_transformers community/langchain_community
mv langchain/langchain/embeddings community/langchain_community
mv langchain/langchain/graphs community/langchain_community
mv langchain/langchain/llms community/langchain_community
mv langchain/langchain/memory/chat_message_histories community/langchain_community
mv langchain/langchain/retrievers community/langchain_community
mv langchain/langchain/storage community/langchain_community
mv langchain/langchain/tools community/langchain_community
mv langchain/langchain/utilities community/langchain_community
mv langchain/langchain/vectorstores community/langchain_community
mv langchain/langchain/agents/agent_toolkits community/langchain_community
mv langchain/langchain/cache.py community/langchain_community
```

Moved the following to core
```
mv langchain/langchain/utils/json_schema.py core/langchain_core/utils
mv langchain/langchain/utils/html.py core/langchain_core/utils
mv langchain/langchain/utils/strings.py core/langchain_core/utils
cat langchain/langchain/utils/env.py >> core/langchain_core/utils/env.py
rm langchain/langchain/utils/env.py
```

See .scripts/community_split/script_integrations.sh for all changes

libs/community/langchain_community/document_loaders/obsidian.py

@@ -0,0 +1,168 @@
+import functools
+import logging
+import re
+from pathlib import Path
+from typing import Any, Dict, List
+
+import yaml
+from langchain_core.documents import Document
+
+from langchain_community.document_loaders.base import BaseLoader
+
+logger = logging.getLogger(__name__)
+
+
+class ObsidianLoader(BaseLoader):
+    """Load `Obsidian` files from directory."""
+
+    FRONT_MATTER_REGEX = re.compile(r"^---\n(.*?)\n---\n", re.DOTALL)
+    TEMPLATE_VARIABLE_REGEX = re.compile(r"{{(.*?)}}", re.DOTALL)
+    TAG_REGEX = re.compile(r"[^\S\/]#([a-zA-Z_]+[-_/\w]*)")
+    DATAVIEW_LINE_REGEX = re.compile(r"^\s*(\w+)::\s*(.*)$", re.MULTILINE)
+    DATAVIEW_INLINE_BRACKET_REGEX = re.compile(r"\[(\w+)::\s*(.*)\]", re.MULTILINE)
+    DATAVIEW_INLINE_PAREN_REGEX = re.compile(r"\((\w+)::\s*(.*)\)", re.MULTILINE)
+
+    def __init__(
+        self, path: str, encoding: str = "UTF-8", collect_metadata: bool = True
+    ):
+        """Initialize with a path.
+
+        Args:
+            path: Path to the directory containing the Obsidian files.
+            encoding: Charset encoding, defaults to "UTF-8"
+            collect_metadata: Whether to collect metadata from the front matter.
+                Defaults to True.
+        """
+        self.file_path = path
+        self.encoding = encoding
+        self.collect_metadata = collect_metadata
+
+    def _replace_template_var(
+        self, placeholders: Dict[str, str], match: re.Match
+    ) -> str:
+        """Replace a template variable with a placeholder."""
+        placeholder = f"__TEMPLATE_VAR_{len(placeholders)}__"
+        placeholders[placeholder] = match.group(1)
+        return placeholder
+
+    def _restore_template_vars(self, obj: Any, placeholders: Dict[str, str]) -> Any:
+        """Restore template variables replaced with placeholders to original values."""
+        if isinstance(obj, str):
+            for placeholder, value in placeholders.items():
+                obj = obj.replace(placeholder, f"{{{{{value}}}}}")
+        elif isinstance(obj, dict):
+            for key, value in obj.items():
+                obj[key] = self._restore_template_vars(value, placeholders)
+        elif isinstance(obj, list):
+            for i, item in enumerate(obj):
+                obj[i] = self._restore_template_vars(item, placeholders)
+        return obj
+
+    def _parse_front_matter(self, content: str) -> dict:
+        """Parse front matter metadata from the content and return it as a dict."""
+        if not self.collect_metadata:
+            return {}
+
+        match = self.FRONT_MATTER_REGEX.search(content)
+        if not match:
+            return {}
+
+        placeholders: Dict[str, str] = {}
+        replace_template_var = functools.partial(
+            self._replace_template_var, placeholders
+        )
+        front_matter_text = self.TEMPLATE_VARIABLE_REGEX.sub(
+            replace_template_var, match.group(1)
+        )
+
+        try:
+            front_matter = yaml.safe_load(front_matter_text)
+            front_matter = self._restore_template_vars(front_matter, placeholders)
+
+            # If tags are a string, split them into a list
+            if "tags" in front_matter and isinstance(front_matter["tags"], str):
+                front_matter["tags"] = front_matter["tags"].split(", ")
+
+            return front_matter
+        except yaml.parser.ParserError:
+            logger.warning("Encountered non-yaml frontmatter")
+            return {}
+
+    def _to_langchain_compatible_metadata(self, metadata: dict) -> dict:
+        """Convert a dictionary to a compatible with langchain."""
+        result = {}
+        for key, value in metadata.items():
+            if type(value) in {str, int, float}:
+                result[key] = value
+            else:
+                result[key] = str(value)
+        return result
+
+    def _parse_document_tags(self, content: str) -> set:
+        """Return a set of all tags in within the document."""
+        if not self.collect_metadata:
+            return set()
+
+        match = self.TAG_REGEX.findall(content)
+        if not match:
+            return set()
+
+        return {tag for tag in match}
+
+    def _parse_dataview_fields(self, content: str) -> dict:
+        """Parse obsidian dataview plugin fields from the content and return it
+        as a dict."""
+        if not self.collect_metadata:
+            return {}
+
+        return {
+            **{
+                match[0]: match[1]
+                for match in self.DATAVIEW_LINE_REGEX.findall(content)
+            },
+            **{
+                match[0]: match[1]
+                for match in self.DATAVIEW_INLINE_PAREN_REGEX.findall(content)
+            },
+            **{
+                match[0]: match[1]
+                for match in self.DATAVIEW_INLINE_BRACKET_REGEX.findall(content)
+            },
+        }
+
+    def _remove_front_matter(self, content: str) -> str:
+        """Remove front matter metadata from the given content."""
+        if not self.collect_metadata:
+            return content
+        return self.FRONT_MATTER_REGEX.sub("", content)
+
+    def load(self) -> List[Document]:
+        """Load documents."""
+        paths = list(Path(self.file_path).glob("**/*.md"))
+        docs = []
+        for path in paths:
+            with open(path, encoding=self.encoding) as f:
+                text = f.read()
+
+            front_matter = self._parse_front_matter(text)
+            tags = self._parse_document_tags(text)
+            dataview_fields = self._parse_dataview_fields(text)
+            text = self._remove_front_matter(text)
+            metadata = {
+                "source": str(path.name),
+                "path": str(path),
+                "created": path.stat().st_ctime,
+                "last_modified": path.stat().st_mtime,
+                "last_accessed": path.stat().st_atime,
+                **self._to_langchain_compatible_metadata(front_matter),
+                **dataview_fields,
+            }
+
+            if tags or front_matter.get("tags"):
+                metadata["tags"] = ",".join(
+                    tags | set(front_matter.get("tags", []) or [])
+                )
+
+            docs.append(Document(page_content=text, metadata=metadata))
+
+        return docs