perl-lsp-diagnostics 0.12.2

LSP diagnostics provider for Perl
Documentation 
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//! Deprecated syntax lint checks
//!
//! This module provides functionality for detecting deprecated Perl syntax
//! and generating appropriate diagnostic warnings.
//!
//! # Diagnostic codes
//!
//! | Code | Severity | Description |
//! |------|----------|-------------|
//! | `deprecated-defined` | Warning | `defined(@array)` or `defined(%hash)` is deprecated |
//! | `deprecated-array-base` | Warning | `$[` variable is deprecated since Perl 5.12 |

use perl_diagnostics_codes::DiagnosticCode;
use perl_parser_core::ast::{Node, NodeKind};

use super::super::walker::walk_node;
use perl_lsp_diagnostic_types::{
    Diagnostic, DiagnosticSeverity, DiagnosticTag, RelatedInformation,
};

/// Check for deprecated syntax
///
/// This function walks the AST looking for deprecated Perl syntax such as:
/// - `defined @array` or `defined %hash`
/// - Use of `$[` variable
pub fn check_deprecated_syntax(node: &Node, diagnostics: &mut Vec<Diagnostic>) {
    walk_node(node, &mut |n| {
        match &n.kind {
            // Check for deprecated 'defined @array' or 'defined %hash'
            NodeKind::FunctionCall { name, args } => {
                if name == "defined"
                    && let Some(arg) = args.first()
                    && let NodeKind::Variable { sigil, name } = &arg.kind
                    && (sigil == "@" || sigil == "%")
                {
                    let type_name = if sigil == "@" { "array" } else { "hash" };
                    diagnostics.push(Diagnostic {
                        range: (n.location.start, n.location.end),
                        severity: DiagnosticSeverity::Warning,
                        code: Some(DiagnosticCode::DeprecatedDefined.as_str().to_string()),
                        message: format!(
                            "Use of 'defined {}{}' is deprecated",
                            sigil, name
                        ),
                        related_information: vec![
                            RelatedInformation {
                                location: (arg.location.start, arg.location.end),
                                message: format!("💡 Use 'if ({}{})'  or 'if ({}{}[0])' instead", sigil, name, sigil, name),
                            },
                            RelatedInformation {
                                location: (n.location.start, n.location.end),
                                message: format!("ℹ️ Testing definedness of {} is deprecated because it was rarely useful and often wrong. Empty {}s are false in boolean context.", type_name, type_name),
                            }
                        ],
                        tags: vec![DiagnosticTag::Deprecated],
                        suggestion: Some(format!("Replace with 'if ({}{})'", sigil, name)),
                    });
                }
            }

            // Check for deprecated $[ variable
            NodeKind::Variable { sigil, name } => {
                if sigil == "$" && name == "[" {
                    diagnostics.push(Diagnostic {
                        range: (n.location.start, n.location.start + 2),
                        severity: DiagnosticSeverity::Warning,
                        code: Some(DiagnosticCode::DeprecatedArrayBase.as_str().to_string()),
                        message: "Use of '$[' is deprecated and will be removed".to_string(),
                        related_information: vec![
                            RelatedInformation {
                                location: (n.location.start, n.location.start + 2),
                                message: "💡 Remove usage of '$[' - arrays always start at index 0".to_string(),
                            },
                            RelatedInformation {
                                location: (n.location.start, n.location.start + 2),
                                message: "ℹ️ The $[ variable was used to change the base index of arrays, but this feature has been deprecated since Perl 5.12 and will be removed in future versions.".to_string(),
                            }
                        ],
                        tags: vec![DiagnosticTag::Deprecated],
                        suggestion: Some("Remove '$[' -- arrays always start at index 0".to_string()),
                    });
                }
            }

            _ => {}
        }
    });
}