fallow_core/analyze/

mod.rs

mod package_json_utils;
mod predicates;
mod unused_deps;
mod unused_exports;
mod unused_files;
mod unused_members;

use rustc_hash::FxHashMap;

use fallow_config::{PackageJson, ResolvedConfig, Severity};

use crate::discover::FileId;
use crate::extract::ModuleInfo;
use crate::graph::ModuleGraph;
use crate::resolve::ResolvedModule;
use crate::results::{AnalysisResults, CircularDependency};
use crate::suppress::{self, IssueKind, Suppression};

use unused_deps::{
    find_test_only_dependencies, find_type_only_dependencies, find_unlisted_dependencies,
    find_unresolved_imports, find_unused_dependencies,
};
use unused_exports::{collect_export_usages, find_duplicate_exports, find_unused_exports};
use unused_files::find_unused_files;
use unused_members::find_unused_members;

/// Pre-computed line offset tables indexed by `FileId`, built during parse and
/// carried through the cache. Eliminates redundant file reads during analysis.
pub(crate) type LineOffsetsMap<'a> = FxHashMap<FileId, &'a [u32]>;

/// Convert a byte offset to (line, col) using pre-computed line offsets.
/// Falls back to `(1, byte_offset)` when no line table is available.
pub(crate) fn byte_offset_to_line_col(
    line_offsets_map: &LineOffsetsMap<'_>,
    file_id: FileId,
    byte_offset: u32,
) -> (u32, u32) {
    line_offsets_map
        .get(&file_id)
        .map_or((1, byte_offset), |offsets| {
            fallow_types::extract::byte_offset_to_line_col(offsets, byte_offset)
        })
}

/// Read source content from disk, returning empty string on failure.
/// Only used for LSP Code Lens reference resolution where the referencing
/// file may not be in the line offsets map.
fn read_source(path: &std::path::Path) -> String {
    std::fs::read_to_string(path).unwrap_or_default()
}

/// Find all dead code in the project.
#[must_use]
pub fn find_dead_code(graph: &ModuleGraph, config: &ResolvedConfig) -> AnalysisResults {
    find_dead_code_with_resolved(graph, config, &[], None)
}

/// Find all dead code, with optional resolved module data and plugin context.
#[must_use]
pub fn find_dead_code_with_resolved(
    graph: &ModuleGraph,
    config: &ResolvedConfig,
    resolved_modules: &[ResolvedModule],
    plugin_result: Option<&crate::plugins::AggregatedPluginResult>,
) -> AnalysisResults {
    find_dead_code_full(
        graph,
        config,
        resolved_modules,
        plugin_result,
        &[],
        &[],
        false,
    )
}

/// Find all dead code, with optional resolved module data, plugin context, and workspace info.
pub fn find_dead_code_full(
    graph: &ModuleGraph,
    config: &ResolvedConfig,
    resolved_modules: &[ResolvedModule],
    plugin_result: Option<&crate::plugins::AggregatedPluginResult>,
    workspaces: &[fallow_config::WorkspaceInfo],
    modules: &[ModuleInfo],
    collect_usages: bool,
) -> AnalysisResults {
    let _span = tracing::info_span!("find_dead_code").entered();

    // Build suppression index: FileId -> suppressions
    let suppressions_by_file: FxHashMap<FileId, &[Suppression]> = modules
        .iter()
        .filter(|m| !m.suppressions.is_empty())
        .map(|m| (m.file_id, m.suppressions.as_slice()))
        .collect();

    // Build line offset index: FileId -> pre-computed line start offsets.
    // Eliminates redundant file reads for byte-to-line/col conversion.
    let line_offsets_by_file: LineOffsetsMap<'_> = modules
        .iter()
        .filter(|m| !m.line_offsets.is_empty())
        .map(|m| (m.file_id, m.line_offsets.as_slice()))
        .collect();

    let mut results = AnalysisResults::default();

    if config.rules.unused_files != Severity::Off {
        results.unused_files = find_unused_files(graph, &suppressions_by_file);
    }

    if config.rules.unused_exports != Severity::Off || config.rules.unused_types != Severity::Off {
        let (exports, types) = find_unused_exports(
            graph,
            config,
            plugin_result,
            &suppressions_by_file,
            &line_offsets_by_file,
        );
        if config.rules.unused_exports != Severity::Off {
            results.unused_exports = exports;
        }
        if config.rules.unused_types != Severity::Off {
            results.unused_types = types;
        }
    }

    if config.rules.unused_enum_members != Severity::Off
        || config.rules.unused_class_members != Severity::Off
    {
        let (enum_members, class_members) = find_unused_members(
            graph,
            resolved_modules,
            &suppressions_by_file,
            &line_offsets_by_file,
        );
        if config.rules.unused_enum_members != Severity::Off {
            results.unused_enum_members = enum_members;
        }
        if config.rules.unused_class_members != Severity::Off {
            results.unused_class_members = class_members;
        }
    }

    // Build merged dependency set from root + all workspace package.json files
    let pkg_path = config.root.join("package.json");
    let pkg = PackageJson::load(&pkg_path).ok();
    if let Some(ref pkg) = pkg {
        if config.rules.unused_dependencies != Severity::Off
            || config.rules.unused_dev_dependencies != Severity::Off
            || config.rules.unused_optional_dependencies != Severity::Off
        {
            let (deps, dev_deps, optional_deps) =
                find_unused_dependencies(graph, pkg, config, plugin_result, workspaces);
            if config.rules.unused_dependencies != Severity::Off {
                results.unused_dependencies = deps;
            }
            if config.rules.unused_dev_dependencies != Severity::Off {
                results.unused_dev_dependencies = dev_deps;
            }
            if config.rules.unused_optional_dependencies != Severity::Off {
                results.unused_optional_dependencies = optional_deps;
            }
        }

        if config.rules.unlisted_dependencies != Severity::Off {
            results.unlisted_dependencies = find_unlisted_dependencies(
                graph,
                pkg,
                config,
                workspaces,
                plugin_result,
                resolved_modules,
                &line_offsets_by_file,
            );
        }
    }

    if config.rules.unresolved_imports != Severity::Off && !resolved_modules.is_empty() {
        let virtual_prefixes: Vec<&str> = plugin_result
            .map(|pr| {
                pr.virtual_module_prefixes
                    .iter()
                    .map(String::as_str)
                    .collect()
            })
            .unwrap_or_default();
        let generated_patterns: Vec<&str> = plugin_result
            .map(|pr| {
                pr.generated_import_patterns
                    .iter()
                    .map(String::as_str)
                    .collect()
            })
            .unwrap_or_default();
        results.unresolved_imports = find_unresolved_imports(
            resolved_modules,
            config,
            &suppressions_by_file,
            &virtual_prefixes,
            &generated_patterns,
            &line_offsets_by_file,
        );
    }

    if config.rules.duplicate_exports != Severity::Off {
        results.duplicate_exports =
            find_duplicate_exports(graph, &suppressions_by_file, &line_offsets_by_file);
    }

    // In production mode, detect dependencies that are only used via type-only imports
    if config.production
        && let Some(ref pkg) = pkg
    {
        results.type_only_dependencies =
            find_type_only_dependencies(graph, pkg, config, workspaces);
    }

    // In non-production mode, detect production deps only imported by test/dev files
    if !config.production
        && config.rules.test_only_dependencies != Severity::Off
        && let Some(ref pkg) = pkg
    {
        results.test_only_dependencies =
            find_test_only_dependencies(graph, pkg, config, workspaces);
    }

    // Detect circular dependencies
    if config.rules.circular_dependencies != Severity::Off {
        let cycles = graph.find_cycles();
        results.circular_dependencies = cycles
            .into_iter()
            .filter(|cycle| {
                // Skip cycles where any participating file has a file-level suppression
                !cycle.iter().any(|&id| {
                    suppressions_by_file.get(&id).is_some_and(|supps| {
                        suppress::is_file_suppressed(supps, IssueKind::CircularDependency)
                    })
                })
            })
            .map(|cycle| {
                let files: Vec<std::path::PathBuf> = cycle
                    .iter()
                    .map(|&id| graph.modules[id.0 as usize].path.clone())
                    .collect();
                let length = files.len();
                // Look up the import span from cycle[0] → cycle[1] for precise location
                let (line, col) = if cycle.len() >= 2 {
                    graph
                        .find_import_span_start(cycle[0], cycle[1])
                        .map_or((1, 0), |span_start| {
                            byte_offset_to_line_col(&line_offsets_by_file, cycle[0], span_start)
                        })
                } else {
                    (1, 0)
                };
                CircularDependency {
                    files,
                    length,
                    line,
                    col,
                }
            })
            .collect();
    }

    // Collect export usage counts for Code Lens (LSP feature).
    // Skipped in CLI mode since the field is #[serde(skip)] in all output formats.
    if collect_usages {
        results.export_usages = collect_export_usages(graph, &line_offsets_by_file);
    }

    results
}

#[cfg(test)]
mod tests {
    use fallow_types::extract::{byte_offset_to_line_col, compute_line_offsets};

    // Helper: compute line offsets from source and convert byte offset
    fn line_col(source: &str, byte_offset: u32) -> (u32, u32) {
        let offsets = compute_line_offsets(source);
        byte_offset_to_line_col(&offsets, byte_offset)
    }

    // ── compute_line_offsets ─────────────────────────────────────

    #[test]
    fn compute_offsets_empty() {
        assert_eq!(compute_line_offsets(""), vec![0]);
    }

    #[test]
    fn compute_offsets_single_line() {
        assert_eq!(compute_line_offsets("hello"), vec![0]);
    }

    #[test]
    fn compute_offsets_multiline() {
        assert_eq!(compute_line_offsets("abc\ndef\nghi"), vec![0, 4, 8]);
    }

    #[test]
    fn compute_offsets_trailing_newline() {
        assert_eq!(compute_line_offsets("abc\n"), vec![0, 4]);
    }

    #[test]
    fn compute_offsets_crlf() {
        assert_eq!(compute_line_offsets("ab\r\ncd"), vec![0, 4]);
    }

    #[test]
    fn compute_offsets_consecutive_newlines() {
        assert_eq!(compute_line_offsets("\n\n"), vec![0, 1, 2]);
    }

    // ── byte_offset_to_line_col ─────────────────────────────────

    #[test]
    fn byte_offset_empty_source() {
        assert_eq!(line_col("", 0), (1, 0));
    }

    #[test]
    fn byte_offset_single_line_start() {
        assert_eq!(line_col("hello", 0), (1, 0));
    }

    #[test]
    fn byte_offset_single_line_middle() {
        assert_eq!(line_col("hello", 4), (1, 4));
    }

    #[test]
    fn byte_offset_multiline_start_of_line2() {
        assert_eq!(line_col("line1\nline2\nline3", 6), (2, 0));
    }

    #[test]
    fn byte_offset_multiline_middle_of_line3() {
        assert_eq!(line_col("line1\nline2\nline3", 14), (3, 2));
    }

    #[test]
    fn byte_offset_at_newline_boundary() {
        assert_eq!(line_col("line1\nline2", 5), (1, 5));
    }

    #[test]
    fn byte_offset_multibyte_utf8() {
        let source = "hi\n\u{1F600}x";
        assert_eq!(line_col(source, 3), (2, 0));
        assert_eq!(line_col(source, 7), (2, 4));
    }

    #[test]
    fn byte_offset_multibyte_accented_chars() {
        let source = "caf\u{00E9}\nbar";
        assert_eq!(line_col(source, 6), (2, 0));
        assert_eq!(line_col(source, 3), (1, 3));
    }

    #[test]
    fn byte_offset_via_map_fallback() {
        use super::*;
        let map: LineOffsetsMap<'_> = FxHashMap::default();
        assert_eq!(
            super::byte_offset_to_line_col(&map, FileId(99), 42),
            (1, 42)
        );
    }

    #[test]
    fn byte_offset_via_map_lookup() {
        use super::*;
        let offsets = compute_line_offsets("abc\ndef\nghi");
        let mut map: LineOffsetsMap<'_> = FxHashMap::default();
        map.insert(FileId(0), &offsets);
        assert_eq!(super::byte_offset_to_line_col(&map, FileId(0), 5), (2, 1));
    }

    // ── find_dead_code orchestration ──────────────────────────────

    mod orchestration {
        use super::super::*;
        use fallow_config::{
            DuplicatesConfig, FallowConfig, HealthConfig, OutputFormat, RulesConfig, Severity,
        };
        use std::path::PathBuf;

        fn make_config_with_rules(rules: RulesConfig) -> ResolvedConfig {
            FallowConfig {
                schema: None,
                extends: vec![],
                entry: vec![],
                ignore_patterns: vec![],
                framework: vec![],
                workspaces: None,
                ignore_dependencies: vec![],
                ignore_exports: vec![],
                duplicates: DuplicatesConfig::default(),
                health: HealthConfig::default(),
                rules,
                production: false,
                plugins: vec![],
                overrides: vec![],
                regression: None,
            }
            .resolve(
                PathBuf::from("/tmp/orchestration-test"),
                OutputFormat::Human,
                1,
                true,
                true,
            )
        }

        #[test]
        fn find_dead_code_all_rules_off_returns_empty() {
            use crate::discover::{DiscoveredFile, EntryPoint, EntryPointSource, FileId};
            use crate::graph::ModuleGraph;
            use crate::resolve::ResolvedModule;
            use rustc_hash::FxHashSet;

            let files = vec![DiscoveredFile {
                id: FileId(0),
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                size_bytes: 100,
            }];
            let entry_points = vec![EntryPoint {
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                source: EntryPointSource::ManualEntry,
            }];
            let resolved = vec![ResolvedModule {
                file_id: FileId(0),
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                exports: vec![],
                re_exports: vec![],
                resolved_imports: vec![],
                resolved_dynamic_imports: vec![],
                resolved_dynamic_patterns: vec![],
                member_accesses: vec![],
                whole_object_uses: vec![],
                has_cjs_exports: false,
                unused_import_bindings: FxHashSet::default(),
            }];
            let graph = ModuleGraph::build(&resolved, &entry_points, &files);

            let rules = RulesConfig {
                unused_files: Severity::Off,
                unused_exports: Severity::Off,
                unused_types: Severity::Off,
                unused_dependencies: Severity::Off,
                unused_dev_dependencies: Severity::Off,
                unused_optional_dependencies: Severity::Off,
                unused_enum_members: Severity::Off,
                unused_class_members: Severity::Off,
                unresolved_imports: Severity::Off,
                unlisted_dependencies: Severity::Off,
                duplicate_exports: Severity::Off,
                type_only_dependencies: Severity::Off,
                circular_dependencies: Severity::Off,
                test_only_dependencies: Severity::Off,
            };
            let config = make_config_with_rules(rules);
            let results = find_dead_code(&graph, &config);

            assert!(results.unused_files.is_empty());
            assert!(results.unused_exports.is_empty());
            assert!(results.unused_types.is_empty());
            assert!(results.unused_dependencies.is_empty());
            assert!(results.unused_dev_dependencies.is_empty());
            assert!(results.unused_optional_dependencies.is_empty());
            assert!(results.unused_enum_members.is_empty());
            assert!(results.unused_class_members.is_empty());
            assert!(results.unresolved_imports.is_empty());
            assert!(results.unlisted_dependencies.is_empty());
            assert!(results.duplicate_exports.is_empty());
            assert!(results.circular_dependencies.is_empty());
            assert!(results.export_usages.is_empty());
        }

        #[test]
        fn find_dead_code_full_collect_usages_flag() {
            use crate::discover::{DiscoveredFile, EntryPoint, EntryPointSource, FileId};
            use crate::extract::ExportName;
            use crate::graph::{ExportSymbol, ModuleGraph};
            use crate::resolve::ResolvedModule;
            use oxc_span::Span;
            use rustc_hash::FxHashSet;

            let files = vec![DiscoveredFile {
                id: FileId(0),
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                size_bytes: 100,
            }];
            let entry_points = vec![EntryPoint {
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                source: EntryPointSource::ManualEntry,
            }];
            let resolved = vec![ResolvedModule {
                file_id: FileId(0),
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                exports: vec![],
                re_exports: vec![],
                resolved_imports: vec![],
                resolved_dynamic_imports: vec![],
                resolved_dynamic_patterns: vec![],
                member_accesses: vec![],
                whole_object_uses: vec![],
                has_cjs_exports: false,
                unused_import_bindings: FxHashSet::default(),
            }];
            let mut graph = ModuleGraph::build(&resolved, &entry_points, &files);
            graph.modules[0].exports = vec![ExportSymbol {
                name: ExportName::Named("myExport".to_string()),
                is_type_only: false,
                is_public: false,
                span: Span::new(10, 30),
                references: vec![],
                members: vec![],
            }];

            let rules = RulesConfig::default();
            let config = make_config_with_rules(rules);

            // Without collect_usages
            let results_no_collect = find_dead_code_full(
                &graph,
                &config,
                &[],
                None,
                &[],
                &[],
                false, // collect_usages = false
            );
            assert!(
                results_no_collect.export_usages.is_empty(),
                "export_usages should be empty when collect_usages is false"
            );

            // With collect_usages
            let results_with_collect = find_dead_code_full(
                &graph,
                &config,
                &[],
                None,
                &[],
                &[],
                true, // collect_usages = true
            );
            assert!(
                !results_with_collect.export_usages.is_empty(),
                "export_usages should be populated when collect_usages is true"
            );
            assert_eq!(
                results_with_collect.export_usages[0].export_name,
                "myExport"
            );
        }

        #[test]
        fn find_dead_code_delegates_to_find_dead_code_with_resolved() {
            use crate::discover::{DiscoveredFile, EntryPoint, EntryPointSource, FileId};
            use crate::graph::ModuleGraph;
            use crate::resolve::ResolvedModule;
            use rustc_hash::FxHashSet;

            let files = vec![DiscoveredFile {
                id: FileId(0),
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                size_bytes: 100,
            }];
            let entry_points = vec![EntryPoint {
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                source: EntryPointSource::ManualEntry,
            }];
            let resolved = vec![ResolvedModule {
                file_id: FileId(0),
                path: PathBuf::from("/tmp/orchestration-test/src/index.ts"),
                exports: vec![],
                re_exports: vec![],
                resolved_imports: vec![],
                resolved_dynamic_imports: vec![],
                resolved_dynamic_patterns: vec![],
                member_accesses: vec![],
                whole_object_uses: vec![],
                has_cjs_exports: false,
                unused_import_bindings: FxHashSet::default(),
            }];
            let graph = ModuleGraph::build(&resolved, &entry_points, &files);
            let config = make_config_with_rules(RulesConfig::default());

            // find_dead_code is a thin wrapper — verify it doesn't panic and returns results
            let results = find_dead_code(&graph, &config);
            // The entry point export analysis is skipped, so these should be empty
            assert!(results.unused_exports.is_empty());
        }

        #[test]
        fn suppressions_built_from_modules() {
            use crate::discover::{DiscoveredFile, EntryPoint, EntryPointSource, FileId};
            use crate::extract::ModuleInfo;
            use crate::graph::ModuleGraph;
            use crate::resolve::ResolvedModule;
            use crate::suppress::{IssueKind, Suppression};
            use rustc_hash::FxHashSet;

            let files = vec![
                DiscoveredFile {
                    id: FileId(0),
                    path: PathBuf::from("/tmp/orchestration-test/src/entry.ts"),
                    size_bytes: 100,
                },
                DiscoveredFile {
                    id: FileId(1),
                    path: PathBuf::from("/tmp/orchestration-test/src/utils.ts"),
                    size_bytes: 100,
                },
            ];
            let entry_points = vec![EntryPoint {
                path: PathBuf::from("/tmp/orchestration-test/src/entry.ts"),
                source: EntryPointSource::ManualEntry,
            }];
            let resolved = files
                .iter()
                .map(|f| ResolvedModule {
                    file_id: f.id,
                    path: f.path.clone(),
                    exports: vec![],
                    re_exports: vec![],
                    resolved_imports: vec![],
                    resolved_dynamic_imports: vec![],
                    resolved_dynamic_patterns: vec![],
                    member_accesses: vec![],
                    whole_object_uses: vec![],
                    has_cjs_exports: false,
                    unused_import_bindings: FxHashSet::default(),
                })
                .collect::<Vec<_>>();
            let graph = ModuleGraph::build(&resolved, &entry_points, &files);

            // Create module info with a file-level suppression for unused files
            let modules = vec![ModuleInfo {
                file_id: FileId(1),
                exports: vec![],
                imports: vec![],
                re_exports: vec![],
                dynamic_imports: vec![],
                dynamic_import_patterns: vec![],
                require_calls: vec![],
                member_accesses: vec![],
                whole_object_uses: vec![],
                has_cjs_exports: false,
                content_hash: 0,
                suppressions: vec![Suppression {
                    line: 0,
                    kind: Some(IssueKind::UnusedFile),
                }],
                unused_import_bindings: vec![],
                line_offsets: vec![],
                complexity: vec![],
            }];

            let rules = RulesConfig {
                unused_files: Severity::Error,
                ..RulesConfig::default()
            };
            let config = make_config_with_rules(rules);

            let results = find_dead_code_full(&graph, &config, &[], None, &[], &modules, false);

            // The suppression should prevent utils.ts from being reported as unused
            // (it would normally be unused since only entry.ts is an entry point).
            // Note: unused_files also checks if the file exists on disk, so it
            // may still be filtered out. The key is the suppression path is exercised.
            assert!(
                !results
                    .unused_files
                    .iter()
                    .any(|f| f.path.to_string_lossy().contains("utils.ts")),
                "suppressed file should not appear in unused_files"
            );
        }
    }
}