Static analysis

Static analysis is the process of evaluating code without executing it. As mentioned in the introduction, PSScriptAnalyzer uses static analysis.

In PowerShell, static analysis most often makes use of an Abstract Syntax Tree (AST): a tree-like representation of a piece of code. In PowerShell, an element of a script is represented by a node in the syntax tree. AST was introduced with PowerShell 3.

The largest elements represent the script itself, the root of the tree in effect. Each element added to the script is represented by a child node. For example, the parameter block is described by a ParamBlockAst object, an individual parameter by a ParameterAst, and so on.

A simple script block can be used as an example:

$scriptBlock = {
    param ( $String )
    Write-Host $String
}

This simple script block contains the nodes shown in Figure 21.1:

Figure 21.1: AST nodes

If the script had more than one parameter, more ParameterAst nodes would...