cpf/enhancement: Implement import extraction with tree-sitter

sourcecode-parser/graph/callgraph/imports.go

@@ -0,0 +1,172 @@
+package callgraph
+
+import (
+	"context"
+
+	sitter "github.com/smacker/go-tree-sitter"
+	"github.com/smacker/go-tree-sitter/python"
+)
+
+// ExtractImports extracts all import statements from a Python file and builds an ImportMap.
+// It handles three main import styles:
+//  1. Simple imports: import module
+//  2. From imports: from module import name
+//  3. Aliased imports: from module import name as alias
+//
+// The resulting ImportMap maps local names (aliases or imported names) to their
+// fully qualified module paths, enabling later resolution of function calls.
+//
+// Algorithm:
+//  1. Parse source code with tree-sitter Python parser
+//  2. Execute tree-sitter query to find all import statements
+//  3. Process each import match to extract module paths and aliases
+//  4. Build ImportMap with resolved fully qualified names
+//
+// Parameters:
+//   - filePath: absolute path to the Python file being analyzed
+//   - sourceCode: contents of the Python file as byte array
+//   - registry: module registry for resolving module paths
+//
+// Returns:
+//   - ImportMap: map of local names to fully qualified module paths
+//   - error: if parsing fails or source is invalid
+//
+// Example:
+//
+//	Source code:
+//	  import os
+//	  from myapp.utils import sanitize
+//	  from myapp.db import query as db_query
+//
+//	Result ImportMap:
+//	  {
+//	    "os": "os",
+//	    "sanitize": "myapp.utils.sanitize",
+//	    "db_query": "myapp.db.query"
+//	  }
+func ExtractImports(filePath string, sourceCode []byte, registry *ModuleRegistry) (*ImportMap, error) {
+	importMap := NewImportMap(filePath)
+
+	// Parse with tree-sitter
+	parser := sitter.NewParser()
+	parser.SetLanguage(python.GetLanguage())
+	defer parser.Close()
+
+	tree, err := parser.ParseCtx(context.Background(), nil, sourceCode)
+	if err != nil {
+		return nil, err
+	}
+	defer tree.Close()
+
+	// Traverse AST to find import statements
+	traverseForImports(tree.RootNode(), sourceCode, importMap)
+
+	return importMap, nil
+}
+
+// traverseForImports recursively traverses the AST to find import statements.
+// Uses direct AST traversal instead of queries for better compatibility.
+func traverseForImports(node *sitter.Node, sourceCode []byte, importMap *ImportMap) {
+	if node == nil {
+		return
+	}
+
+	nodeType := node.Type()
+
+	// Process import statements
+	switch nodeType {
+	case "import_statement":
+		processImportStatement(node, sourceCode, importMap)
+		// Don't recurse into children - we've already processed this import
+		return
+	case "import_from_statement":
+		processImportFromStatement(node, sourceCode, importMap)
+		// Don't recurse into children - we've already processed this import
+		return
+	}
+
+	// Recursively process children
+	for i := 0; i < int(node.ChildCount()); i++ {
+		child := node.Child(i)
+		traverseForImports(child, sourceCode, importMap)
+	}
+}
+
+// processImportStatement handles simple import statements: import module [as alias].
+// Examples:
+//   - import os → "os" = "os"
+//   - import os as op → "op" = "os"
+func processImportStatement(node *sitter.Node, sourceCode []byte, importMap *ImportMap) {
+	// Look for 'name' field which contains the import
+	nameNode := node.ChildByFieldName("name")
+	if nameNode == nil {
+		return
+	}
+
+	// Check if it's an aliased import
+	if nameNode.Type() == "aliased_import" {
+		// import module as alias
+		moduleNode := nameNode.ChildByFieldName("name")
+		aliasNode := nameNode.ChildByFieldName("alias")
+
+		if moduleNode != nil && aliasNode != nil {
+			moduleName := moduleNode.Content(sourceCode)
+			aliasName := aliasNode.Content(sourceCode)
+			importMap.AddImport(aliasName, moduleName)
+		}
+	} else if nameNode.Type() == "dotted_name" {
+		// Simple import: import module
+		moduleName := nameNode.Content(sourceCode)
+		importMap.AddImport(moduleName, moduleName)
+	}
+}
+
+// processImportFromStatement handles from-import statements: from module import name [as alias].
+// Examples:
+//   - from os import path → "path" = "os.path"
+//   - from os import path as ospath → "ospath" = "os.path"
+//   - from json import dumps, loads → "dumps" = "json.dumps", "loads" = "json.loads"
+func processImportFromStatement(node *sitter.Node, sourceCode []byte, importMap *ImportMap) {
+	// Get the module being imported from
+	moduleNameNode := node.ChildByFieldName("module_name")
+	if moduleNameNode == nil {
+		return
+	}
+
+	moduleName := moduleNameNode.Content(sourceCode)
+
+	// The 'name' field might be:
+	// 1. A single dotted_name: from os import path
+	// 2. A single aliased_import: from os import path as ospath
+	// 3. A wildcard_import: from os import *
+	//
+	// For multiple imports (from json import dumps, loads), tree-sitter
+	// creates multiple child nodes, so we need to check all children
+	for i := 0; i < int(node.ChildCount()); i++ {
+		child := node.Child(i)
+
+		// Skip the module_name node itself - we only want the imported names
+		if child == moduleNameNode {
+			continue
+		}
+
+		// Process each import name/alias
+		if child.Type() == "aliased_import" {
+			// from module import name as alias
+			importNameNode := child.ChildByFieldName("name")
+			aliasNode := child.ChildByFieldName("alias")
+
+			if importNameNode != nil && aliasNode != nil {
+				importName := importNameNode.Content(sourceCode)
+				aliasName := aliasNode.Content(sourceCode)
+				fqn := moduleName + "." + importName
+				importMap.AddImport(aliasName, fqn)
+			}
+		} else if child.Type() == "dotted_name" || child.Type() == "identifier" {
+			// from module import name
+			importName := child.Content(sourceCode)
+			fqn := moduleName + "." + importName
+			importMap.AddImport(importName, fqn)
+		}
+	}
+}