Merge pull request #42 from GitHubSecurityLab/docs-update

docs: Update and improve the AST docs

Author: GeekMasher

ql/lib/codeql/bicep/ast/AstNodes.qll

@@ -6,27 +6,58 @@ private import codeql.bicep.ast.internal.TreeSitter
 private import codeql.bicep.controlflow.ControlFlowGraph
 
 /**
- * An AST node of a Bicep program
+ * An AST node of a Bicep program.
+ * 
+ * This is the base class for all syntax nodes in the Bicep language. All
+ * Bicep entities that have a representation in the abstract syntax tree
+ * (such as expressions, statements, resources, parameters, etc.) extend this class.
  */
 class AstNode extends TAstNode {
   private BICEP::AstNode node;
 
   AstNode() { toTreeSitter(this) = node }
 
+  /**
+   * Gets a string representation of this AST node.
+   * 
+   * By default, returns the primary QL class name of this node.
+   */
   string toString() { result = this.getAPrimaryQlClass() }
 
-  /** Gets the location of the AST node. */
+  /** 
+   * Gets the location of the AST node.
+   * 
+   * The location includes information about the file, and the start and
+   * end positions of the node in the file (line and column).
+   */
   cached
   Location getLocation() { result = this.getFullLocation() } // overridden in some subclasses
 
-  /** Gets the file containing this AST node. */
+  /** 
+   * Gets the file containing this AST node.
+   * 
+   * This is the source file where this AST node is defined.
+   */
   cached
   File getFile() { result = this.getFullLocation().getFile() }
 
-  /** Gets the location that spans the entire AST node. */
+  /** 
+   * Gets the location that spans the entire AST node.
+   * 
+   * This includes the full text range covered by this node and all its children.
+   */
   cached
   final Location getFullLocation() { result = toTreeSitter(this).getLocation() }
 
+  /**
+   * Holds if this AST node has the specified location information.
+   * 
+   * @param filepath The file path
+   * @param startline The start line
+   * @param startcolumn The start column
+   * @param endline The end line
+   * @param endcolumn The end column
+   */
   predicate hasLocationInfo(
     string filepath, int startline, int startcolumn, int endline, int endcolumn
   ) {
@@ -43,18 +74,29 @@ class AstNode extends TAstNode {
 
   /**
    * Gets the parent in the AST for this node.
+   * 
+   * This is the immediately enclosing syntax node in the AST.
+   * For example, the parent of an expression might be a statement that contains it.
    */
   cached
   AstNode getParent() { result.getAChild() = this }
 
   /**
-   * Gets a child of this node, which can also be retrieved using a predicate
-   * named `pred`.
+   * Gets a child of this node.
+   * 
+   * This returns any direct child node in the AST hierarchy.
+   * The exact set of child nodes depends on the specific type of AST node.
    */
   cached
   AstNode getAChild() { toTreeSitter(result) = node.getAFieldOrChild() }
 
-  /** Gets the CFG scope that encloses this node, if any. */
+  /** 
+   * Gets the CFG scope that encloses this node, if any.
+   * 
+   * A CFG scope is a region of code that has its own control flow graph.
+   * This can include the entire file, functions, or other code blocks with
+   * independent control flow.
+   */
   cached
   CfgScope getEnclosingCfgScope() {
     exists(AstNode p | p = this.getParent*() |
@@ -66,19 +108,36 @@ class AstNode extends TAstNode {
   }
 
   /**
-   * Gets the primary QL class for the ast node.
+   * Gets the primary QL class for the AST node.
+   * 
+   * This returns the name of the most specific QL class that describes this node.
+   * Used primarily for debugging and toString() representations.
    */
   string getAPrimaryQlClass() { result = "???" }
 }
 
-/** A Bicep file */
+/** 
+ * A Bicep file.
+ * 
+ * Represents a source file written in the Bicep language. This class provides
+ * access to file metadata and metrics such as the total number of lines and
+ * lines of code.
+ */
 class BicepFile extends File {
   BicepFile() { exists(Location loc | bicep_ast_node_location(_, loc) and this = loc.getFile()) }
 
-  /** Gets a token in this file. */
+  /** 
+   * Gets a token in this file.
+   * 
+   * A token is a basic syntactic unit recognized by the lexer.
+   */
   private BICEP::Token getAToken() { result.getLocation().getFile() = this }
 
-  /** Holds if `line` contains a token. */
+  /** 
+   * Holds if `line` contains a token.
+   * 
+   * This is used to calculate metrics like the number of lines of code.
+   */
   private predicate line(int line) {
     exists(BICEP::Token token, Location l |
       token = this.getAToken() and
@@ -87,15 +146,28 @@ class BicepFile extends File {
     )
   }
 
-  /** Gets the number of lines in this file. */
+  /** 
+   * Gets the number of lines in this file.
+   * 
+   * This counts the total number of lines in the file, including empty lines
+   * and comment lines.
+   */
   int getNumberOfLines() { result = max([0, this.getAToken().getLocation().getEndLine()]) }
 
-  /** Gets the number of lines of code in this file. */
+  /** 
+   * Gets the number of lines of code in this file.
+   * 
+   * This counts only lines that contain at least one token, which excludes
+   * completely empty lines.
+   */
   int getNumberOfLinesOfCode() { result = count(int line | this.line(line)) }
 }
 
 /**
- * A comment in a Bicep program
+ * A comment in a Bicep program.
+ * 
+ * Represents a single- or multi-line comment in Bicep source code.
+ * Comments may be either single-line (// comment) or multi-line (/* comment *\/).
  */
 class Comment extends AstNode, TComment {
   private BICEP::Comment comment;
@@ -105,9 +177,14 @@ class Comment extends AstNode, TComment {
   Comment() { this = TComment(comment) }
 
   /**
-   * Gets the text of the comment.
+   * Gets the text content of the comment.
+   *
+   * For a single-line comment, this is the text after the // delimiter.
+   * For a multi-line comment, this is the text between the /* and *\/ delimiters.
    *
-   * TODO: Implement this method
+   * Note: This method is currently a placeholder and needs implementation.
+   * 
+   * @return The text content of the comment (currently an empty string)
    */
   string getContents() { result = "" }
 }

ql/lib/codeql/bicep/ast/Calls.qll

@@ -7,59 +7,112 @@ private import internal.CallExpression
 
 /**
  * Represents a callable expression in the AST, such as a function or method call.
- * Provides access to the identifier and name of the call expression.
+ * 
+ * This abstract class serves as the base for any expression that represents
+ * a call to a function or method. It provides common functionality for accessing
+ * the name and identifier of the called entity.
  */
 abstract class Callable extends Expr {
   /**
-   *  Gets the identifier of the call expression.
+   * Gets the identifier of the callable expression.
+   * 
+   * This is the name token that identifies what function or method is being called.
+   * 
+   * @return The identifier node of the callable
    */
   abstract Idents getIdentifier();
 
   /**
-   * Gets the name of the call expression.
+   * Gets the name of the callable expression as a string.
+   * 
+   * This is a convenience method that returns the name from the identifier.
    *
-   * @return The name as a string.
+   * @return The name of the callable
    */
   string getName() { result = this.getIdentifier().getName() }
 
   /**
-   * Checks if the call expression has a specific name.
+   * Checks if the callable expression has a specific name.
+   * 
+   * This is useful for identifying calls to known functions by name.
    *
-   * @param name The name to check against.
-   * @return True if the call expression has the given name.
+   * @param name The name to check against
+   * @return True if the callable has the given name, false otherwise
    */
   predicate hasName(string name) { this.getName() = name }
 }
 
 /**
- * Represents a call expression node in the AST.
- * Provides access to the identifier, arguments, and declared arguments.
+ * Represents a function or method call expression in the AST.
+ * 
+ * This class models a function call in Bicep, consisting of an identifier
+ * (the function name) followed by arguments in parentheses. Function calls
+ * invoke functions defined in the language, user-defined functions, or
+ * module functions to compute values or perform operations.
  */
 class CallExpression extends Expr instanceof CallExpressionImpl {
-  /** Gets the identifier of the call expression. */
+  /** 
+   * Gets the identifier of the call expression.
+   * 
+   * This is the name token that identifies what function is being called.
+   * 
+   * @return The identifier node of the function being called
+   */
   Idents getIdentifier() { result = CallExpressionImpl.super.getIdentifier() }
 
-  /** Gets the name of the call expression. */
+  /** 
+   * Gets the name of the call expression as a string.
+   * 
+   * This is a convenience method that returns the name from the identifier.
+   * 
+   * @return The name of the function being called
+   */
   string getName() { result = this.getIdentifier().getName() }
 
-  /** Gets the argument at the specified index. */
+  /** 
+   * Gets the argument at the specified index.
+   * 
+   * @param index The zero-based index of the argument to retrieve
+   * @return The expression node of the argument at the specified index
+   */
   Expr getArgument(int index) { result = this.getDeclaredArguments().getArgument(index) }
 
-  /** Gets all arguments of the call expression. */
+  /** 
+   * Gets all arguments of the call expression.
+   * 
+   * @return All argument expressions passed to the function
+   */
   Expr getArguments() { result = this.getDeclaredArguments().getArguments() }
 
-  /** Gets the declared arguments node. */
+  /** 
+   * Gets the arguments collection node of the call expression.
+   * 
+   * This provides access to the AST node that contains all the arguments.
+   * 
+   * @return The arguments node of the call expression
+   */
   Arguments getDeclaredArguments() { result = CallExpressionImpl.super.getArguments() }
 }
 
 /**
- * Represents the arguments node in the AST.
- * Provides access to individual and all arguments.
+ * Represents a collection of arguments in a function call.
+ * 
+ * This class models the set of arguments passed to a function, allowing
+ * access to individual arguments by index or to the complete set of arguments.
  */
 class Arguments extends AstNode instanceof ArgumentsImpl {
-  /** Gets the argument at the specified index. */
+  /** 
+   * Gets the argument at the specified index.
+   * 
+   * @param index The zero-based index of the argument to retrieve
+   * @return The expression node of the argument at the specified index
+   */
   Expr getArgument(int index) { result = ArgumentsImpl.super.getArgument(index) }
 
-  /** Gets all arguments. */
+  /** 
+   * Gets all arguments in the collection.
+   * 
+   * @return All argument expressions in this arguments collection
+   */
   Expr getArguments() { result = ArgumentsImpl.super.getArguments() }
 }