fallow_extract/

flags.rs

//! Feature flag detection via lightweight Oxc AST visitor.
//!
//! Detects three patterns:
//! 1. **Environment variables**: `process.env.FEATURE_X`
//! 2. **SDK calls**: `useFlag('name')`, `variation('name', false)`,
//!    `flag({ key: 'name' })`, etc.
//! 3. **Config objects**: `config.features.x` (opt-in, heuristic)
//!
//! Always extracted during parse (lightweight pattern matching on `MemberExpression`
//! and `CallExpression` nodes). Custom SDK patterns and config object heuristics
//! are applied as a supplementary pass in the CLI when user config is present.

#[allow(clippy::wildcard_imports, reason = "many AST types used")]
use oxc_ast::ast::*;
use oxc_ast_visit::Visit;
use oxc_ast_visit::walk;
use rustc_hash::{FxHashMap, FxHashSet};

use fallow_types::extract::{FlagUse, FlagUseKind, byte_offset_to_line_col};

/// Built-in SDK function patterns: (function_name, name_arg_index, provider_label).
const BUILTIN_SDK_PATTERNS: &[(&str, usize, &str)] = &[
    ("useFlag", 0, "LaunchDarkly"),
    ("useLDFlag", 0, "LaunchDarkly"),
    ("useFeatureFlag", 0, "LaunchDarkly"),
    ("variation", 0, "LaunchDarkly"),
    ("boolVariation", 0, "LaunchDarkly"),
    ("stringVariation", 0, "LaunchDarkly"),
    ("numberVariation", 0, "LaunchDarkly"),
    ("jsonVariation", 0, "LaunchDarkly"),
    ("useGate", 0, "Statsig"),
    ("checkGate", 0, "Statsig"),
    ("useExperiment", 0, "Statsig"),
    ("useConfig", 0, "Statsig"),
    ("isEnabled", 0, "Unleash"),
    ("getVariant", 0, "Unleash"),
    ("isOn", 0, "GrowthBook"),
    ("isOff", 0, "GrowthBook"),
    ("getFeatureValue", 0, "GrowthBook"),
    ("getTreatment", 0, "Split"),
    ("useFeatureFlagEnabled", 0, "PostHog"),
    ("useFeatureFlagPayload", 0, "PostHog"),
    ("useFeatureFlagVariantKey", 0, "PostHog"),
    ("getFeatureFlagPayload", 0, "PostHog"),
    ("getValueAsync", 0, "ConfigCat"),
    ("getValueDetailsAsync", 0, "ConfigCat"),
    ("hasFeature", 0, "Flagsmith"),
    ("useDecision", 0, "Optimizely"),
    ("getFeatureVariable", 0, "Optimizely"),
    ("getFeatureVariableBoolean", 0, "Optimizely"),
    ("getFeatureVariableString", 0, "Optimizely"),
    ("getFeatureVariableInteger", 0, "Optimizely"),
    ("getFeatureVariableDouble", 0, "Optimizely"),
    ("getFeatureVariableJson", 0, "Optimizely"),
    ("getFeatureVariableJSON", 0, "Optimizely"),
    ("getStringAssignment", 0, "Eppo"),
    ("getBooleanAssignment", 0, "Eppo"),
    ("getNumericAssignment", 0, "Eppo"),
    ("getIntegerAssignment", 0, "Eppo"),
    ("getJSONAssignment", 0, "Eppo"),
    ("getStringAssignmentDetails", 0, "Eppo"),
    ("getBooleanAssignmentDetails", 0, "Eppo"),
    ("getNumericAssignmentDetails", 0, "Eppo"),
    ("getIntegerAssignmentDetails", 0, "Eppo"),
    ("getJSONAssignmentDetails", 0, "Eppo"),
    ("getValue", 0, ""),
    ("useFeature", 0, ""),
    ("getFeatureFlag", 0, ""),
];

const VERCEL_FLAGS_PROVIDER: &str = "Vercel Flags";
const VERCEL_FLAGS_FUNCTIONS: &[&str] = &["flag", "evaluate"];

/// Built-in environment variable prefixes that indicate feature flags.
const BUILTIN_ENV_PREFIXES: &[&str] = &[
    "FEATURE_",
    "NEXT_PUBLIC_FEATURE_",
    "NEXT_PUBLIC_ENABLE_",
    "REACT_APP_FEATURE_",
    "REACT_APP_ENABLE_",
    "VITE_FEATURE_",
    "VITE_ENABLE_",
    "NUXT_PUBLIC_FEATURE_",
    "ENABLE_",
    "FF_",
    "FLAG_",
    "TOGGLE_",
];

/// Distinct built-in SDK provider labels, in declaration order.
///
/// Used by `fallow flags` to tell the user which SDKs the default detectors
/// cover when no flags are found. Derived from `BUILTIN_SDK_PATTERNS` (empty
/// provider labels skipped) with the import-based Vercel Flags provider appended,
/// so the surfaced list stays in sync with what is actually detected.
#[must_use]
pub fn builtin_sdk_providers() -> Vec<&'static str> {
    let mut providers: Vec<&'static str> = Vec::new();
    for &(_, _, provider) in BUILTIN_SDK_PATTERNS {
        if !provider.is_empty() && !providers.contains(&provider) {
            providers.push(provider);
        }
    }
    if !providers.contains(&VERCEL_FLAGS_PROVIDER) {
        providers.push(VERCEL_FLAGS_PROVIDER);
    }
    providers
}

/// Built-in environment variable prefixes treated as feature flags.
///
/// Used by `fallow flags` to surface the default env-prefix detectors in the
/// empty-result hint. Returns the source-of-truth `BUILTIN_ENV_PREFIXES`.
#[must_use]
pub fn builtin_env_prefixes() -> &'static [&'static str] {
    BUILTIN_ENV_PREFIXES
}

/// Config object names that heuristically indicate feature flag namespaces.
const CONFIG_OBJECT_KEYWORDS: &[&str] = &[
    "feature",
    "features",
    "featureFlags",
    "featureFlag",
    "flag",
    "flags",
    "toggle",
    "toggles",
];

/// AST visitor that detects feature flag patterns.
struct FlagVisitor<'a> {
    results: Vec<FlagUse>,
    line_offsets: &'a [u32],
    /// Extra SDK patterns from user config.
    extra_sdk_patterns: &'a [(String, usize, String)],
    /// Extra env prefixes from user config.
    extra_env_prefixes: &'a [String],
    /// Whether to detect config object patterns (opt-in).
    config_object_heuristics: bool,
    /// Local named imports from Vercel Flags packages: local name -> imported name.
    vercel_flags_imports: FxHashMap<String, String>,
    /// Namespace imports from Vercel Flags packages.
    vercel_flags_namespaces: FxHashSet<String>,
}

impl<'a> FlagVisitor<'a> {
    fn new(
        line_offsets: &'a [u32],
        extra_sdk_patterns: &'a [(String, usize, String)],
        extra_env_prefixes: &'a [String],
        config_object_heuristics: bool,
    ) -> Self {
        Self {
            results: Vec::new(),
            line_offsets,
            extra_sdk_patterns,
            extra_env_prefixes,
            config_object_heuristics,
            vercel_flags_imports: FxHashMap::default(),
            vercel_flags_namespaces: FxHashSet::default(),
        }
    }

    /// Check if a member expression matches `process.env.SOMETHING`.
    fn check_env_var(&mut self, expr: &MemberExpression<'_>, guard: Option<(u32, u32)>) {
        if let MemberExpression::StaticMemberExpression(static_expr) = expr
            && let Some(env_name) = extract_process_env_name(static_expr)
            && self.is_flag_env_name(&env_name)
        {
            let (line, col) = byte_offset_to_line_col(self.line_offsets, static_expr.span.start);
            self.results.push(FlagUse {
                flag_name: env_name,
                kind: FlagUseKind::EnvVar,
                line,
                col,
                guard_span_start: guard.map(|(s, _)| s),
                guard_span_end: guard.map(|(_, e)| e),
                sdk_name: None,
            });
        }
    }

    /// Check if a call expression matches an SDK pattern.
    fn check_sdk_call(&mut self, call: &CallExpression<'_>, guard: Option<(u32, u32)>) {
        let func_name = match &call.callee {
            Expression::Identifier(id) => Some(id.name.as_str()),
            Expression::StaticMemberExpression(member) => Some(member.property.name.as_str()),
            _ => None,
        };

        let Some(func_name) = func_name else {
            return;
        };

        if self.check_vercel_flags_call(call, guard) {
            return;
        }

        for &(pattern_name, name_arg_idx, provider) in BUILTIN_SDK_PATTERNS {
            if func_name == pattern_name {
                if let Some(flag_name) = extract_string_arg(&call.arguments, name_arg_idx) {
                    let (line, col) = byte_offset_to_line_col(self.line_offsets, call.span.start);
                    self.results.push(FlagUse {
                        flag_name,
                        kind: FlagUseKind::SdkCall,
                        line,
                        col,
                        guard_span_start: guard.map(|(s, _)| s),
                        guard_span_end: guard.map(|(_, e)| e),
                        sdk_name: if provider.is_empty() {
                            None
                        } else {
                            Some(provider.to_string())
                        },
                    });
                }
                return;
            }
        }

        for (pattern_name, name_arg_idx, provider) in self.extra_sdk_patterns {
            if func_name == pattern_name {
                if let Some(flag_name) = extract_string_arg(&call.arguments, *name_arg_idx) {
                    let (line, col) = byte_offset_to_line_col(self.line_offsets, call.span.start);
                    self.results.push(FlagUse {
                        flag_name,
                        kind: FlagUseKind::SdkCall,
                        line,
                        col,
                        guard_span_start: guard.map(|(s, _)| s),
                        guard_span_end: guard.map(|(_, e)| e),
                        sdk_name: if provider.is_empty() {
                            None
                        } else {
                            Some(provider.clone())
                        },
                    });
                }
                return;
            }
        }
    }

    fn check_vercel_flags_call(
        &mut self,
        call: &CallExpression<'_>,
        guard: Option<(u32, u32)>,
    ) -> bool {
        let Some(imported_name) = self.vercel_flags_imported_name(call) else {
            return false;
        };

        let flag_name = match imported_name {
            "flag" => extract_object_string_property_arg(&call.arguments, 0, "key"),
            "evaluate" => extract_string_arg(&call.arguments, 0),
            _ => None,
        };

        let Some(flag_name) = flag_name else {
            return false;
        };

        let (line, col) = byte_offset_to_line_col(self.line_offsets, call.span.start);
        self.results.push(FlagUse {
            flag_name,
            kind: FlagUseKind::SdkCall,
            line,
            col,
            guard_span_start: guard.map(|(s, _)| s),
            guard_span_end: guard.map(|(_, e)| e),
            sdk_name: Some(VERCEL_FLAGS_PROVIDER.to_string()),
        });
        true
    }

    fn vercel_flags_imported_name<'b>(&'b self, call: &'b CallExpression<'_>) -> Option<&'b str> {
        match &call.callee {
            Expression::Identifier(id) => self
                .vercel_flags_imports
                .get(id.name.as_str())
                .map(String::as_str),
            Expression::StaticMemberExpression(member) => {
                let Expression::Identifier(object) = &member.object else {
                    return None;
                };
                self.vercel_flags_namespaces
                    .contains(object.name.as_str())
                    .then_some(member.property.name.as_str())
            }
            _ => None,
        }
    }

    fn collect_vercel_flags_imports(&mut self, program: &Program<'_>) {
        for stmt in &program.body {
            if let Statement::ImportDeclaration(decl) = stmt {
                self.collect_vercel_flags_import(decl);
            }
        }
    }

    fn collect_vercel_flags_import(&mut self, decl: &ImportDeclaration<'_>) {
        if !is_vercel_flags_source(decl.source.value.as_str()) || decl.import_kind.is_type() {
            return;
        }

        let Some(specifiers) = &decl.specifiers else {
            return;
        };

        for spec in specifiers {
            match spec {
                ImportDeclarationSpecifier::ImportSpecifier(specifier) => {
                    if specifier.import_kind.is_type() {
                        continue;
                    }
                    let imported_name = specifier.imported.name();
                    if VERCEL_FLAGS_FUNCTIONS.contains(&imported_name.as_str()) {
                        self.vercel_flags_imports
                            .insert(specifier.local.name.to_string(), imported_name.to_string());
                    }
                }
                ImportDeclarationSpecifier::ImportNamespaceSpecifier(specifier) => {
                    self.vercel_flags_namespaces
                        .insert(specifier.local.name.to_string());
                }
                ImportDeclarationSpecifier::ImportDefaultSpecifier(_) => {}
            }
        }
    }

    /// Check if a member expression matches a config object pattern.
    fn check_config_object(
        &mut self,
        expr: &StaticMemberExpression<'_>,
        guard: Option<(u32, u32)>,
    ) {
        if !self.config_object_heuristics {
            return;
        }

        if let Some((obj_name, prop_name)) = extract_config_object_access(expr)
            && CONFIG_OBJECT_KEYWORDS
                .iter()
                .any(|kw| obj_name.eq_ignore_ascii_case(kw) || prop_name.eq_ignore_ascii_case(kw))
        {
            let (line, col) = byte_offset_to_line_col(self.line_offsets, expr.span.start);
            self.results.push(FlagUse {
                flag_name: format!("{obj_name}.{prop_name}"),
                kind: FlagUseKind::ConfigObject,
                line,
                col,
                guard_span_start: guard.map(|(s, _)| s),
                guard_span_end: guard.map(|(_, e)| e),
                sdk_name: None,
            });
        }
    }

    fn is_flag_env_name(&self, name: &str) -> bool {
        for prefix in BUILTIN_ENV_PREFIXES {
            if name.starts_with(prefix) {
                return true;
            }
        }
        for prefix in self.extra_env_prefixes {
            if name.starts_with(prefix.as_str()) {
                return true;
            }
        }
        false
    }
}

impl Visit<'_> for FlagVisitor<'_> {
    fn visit_program(&mut self, program: &Program<'_>) {
        self.collect_vercel_flags_imports(program);
        walk::walk_program(self, program);
    }

    fn visit_import_declaration(&mut self, decl: &ImportDeclaration<'_>) {
        self.collect_vercel_flags_import(decl);
    }

    fn visit_if_statement(&mut self, stmt: &IfStatement<'_>) {
        let guard = Some((stmt.span.start, stmt.span.end));

        check_expression_for_flags(self, &stmt.test, guard);

        self.visit_statement(&stmt.consequent);
        if let Some(alt) = &stmt.alternate {
            self.visit_statement(alt);
        }
    }

    fn visit_conditional_expression(&mut self, expr: &ConditionalExpression<'_>) {
        let guard = Some((expr.span.start, expr.span.end));
        check_expression_for_flags(self, &expr.test, guard);

        self.visit_expression(&expr.consequent);
        self.visit_expression(&expr.alternate);
    }

    fn visit_call_expression(&mut self, call: &CallExpression<'_>) {
        self.check_sdk_call(call, None);
        walk::walk_call_expression(self, call);
    }

    fn visit_member_expression(&mut self, expr: &MemberExpression<'_>) {
        self.check_env_var(expr, None);
        if let MemberExpression::StaticMemberExpression(static_expr) = expr {
            self.check_config_object(static_expr, None);
        }
        walk::walk_member_expression(self, expr);
    }
}

fn is_vercel_flags_source(source: &str) -> bool {
    source == "flags"
        || source.starts_with("flags/")
        || source == "@vercel/flags"
        || source.starts_with("@vercel/flags/")
}

/// Check an expression (typically an if-test) for flag patterns.
fn check_expression_for_flags(
    visitor: &mut FlagVisitor<'_>,
    expr: &Expression<'_>,
    guard: Option<(u32, u32)>,
) {
    match expr {
        Expression::CallExpression(call) => {
            visitor.check_sdk_call(call, guard);
        }
        Expression::StaticMemberExpression(member) => {
            check_static_member_for_env(visitor, member, guard);
            visitor.check_config_object(member, guard);
        }
        Expression::UnaryExpression(unary) if unary.operator == UnaryOperator::LogicalNot => {
            check_expression_for_flags(visitor, &unary.argument, guard);
        }
        Expression::LogicalExpression(logical) => {
            check_expression_for_flags(visitor, &logical.left, guard);
            check_expression_for_flags(visitor, &logical.right, guard);
        }
        _ => {}
    }
}

/// Check a static member expression directly for `process.env.X` pattern.
fn check_static_member_for_env(
    visitor: &mut FlagVisitor<'_>,
    expr: &StaticMemberExpression<'_>,
    guard: Option<(u32, u32)>,
) {
    if let Some(env_name) = extract_process_env_name(expr)
        && visitor.is_flag_env_name(&env_name)
    {
        let (line, col) = byte_offset_to_line_col(visitor.line_offsets, expr.span.start);
        visitor.results.push(FlagUse {
            flag_name: env_name,
            kind: FlagUseKind::EnvVar,
            line,
            col,
            guard_span_start: guard.map(|(s, _)| s),
            guard_span_end: guard.map(|(_, e)| e),
            sdk_name: None,
        });
    }
}

/// Extract the environment variable name from `process.env.X`.
fn extract_process_env_name(expr: &StaticMemberExpression<'_>) -> Option<String> {
    let prop_name = expr.property.name.as_str();

    if let Expression::StaticMemberExpression(inner) = &expr.object
        && inner.property.name.as_str() == "env"
        && let Expression::Identifier(id) = &inner.object
        && id.name.as_str() == "process"
    {
        return Some(prop_name.to_string());
    }

    None
}

/// Extract a string literal argument at the given index.
fn extract_string_arg(args: &[Argument<'_>], index: usize) -> Option<String> {
    args.get(index).and_then(|arg| {
        if let Argument::StringLiteral(lit) = arg {
            Some(lit.value.to_string())
        } else {
            None
        }
    })
}

/// Extract a string property from an object argument at the given index.
fn extract_object_string_property_arg(
    args: &[Argument<'_>],
    index: usize,
    property_name: &str,
) -> Option<String> {
    let Some(Argument::ObjectExpression(obj)) = args.get(index) else {
        return None;
    };

    for prop in &obj.properties {
        let ObjectPropertyKind::ObjectProperty(prop) = prop else {
            continue;
        };
        if prop
            .key
            .static_name()
            .is_some_and(|key| key.as_ref() == property_name)
            && let Expression::StringLiteral(lit) = &prop.value
        {
            return Some(lit.value.to_string());
        }
    }

    None
}

/// Extract config object access pattern: `obj.prop` where either name is a flag keyword.
fn extract_config_object_access(expr: &StaticMemberExpression<'_>) -> Option<(String, String)> {
    let prop_name = expr.property.name.to_string();

    match &expr.object {
        Expression::Identifier(id) => Some((id.name.to_string(), prop_name)),
        Expression::StaticMemberExpression(inner) => {
            if matches!(&inner.object, Expression::Identifier(_)) {
                Some((inner.property.name.to_string(), prop_name))
            } else {
                None
            }
        }
        _ => None,
    }
}

/// Entry point: extract feature flag use sites from a parsed program.
///
/// Called unconditionally from `parse_source_to_module` for all parsed files.
pub fn extract_flags(
    program: &Program<'_>,
    line_offsets: &[u32],
    extra_sdk_patterns: &[(String, usize, String)],
    extra_env_prefixes: &[String],
    config_object_heuristics: bool,
) -> Vec<FlagUse> {
    let mut visitor = FlagVisitor::new(
        line_offsets,
        extra_sdk_patterns,
        extra_env_prefixes,
        config_object_heuristics,
    );
    visitor.visit_program(program);
    visitor.results
}

/// Extract feature flags from source text with custom configuration.
///
/// Higher-level convenience function that handles parsing internally.
/// Used by the CLI flags command for supplementary extraction with
/// user-configured patterns that aren't applied at parse/cache time.
pub fn extract_flags_from_source(
    source: &str,
    path: &std::path::Path,
    extra_sdk_patterns: &[(String, usize, String)],
    extra_env_prefixes: &[String],
    config_object_heuristics: bool,
) -> Vec<FlagUse> {
    let source_type = oxc_span::SourceType::from_path(path).unwrap_or_default();
    let allocator = oxc_allocator::Allocator::default();
    let parser_return = oxc_parser::Parser::new(&allocator, source, source_type).parse();
    let line_offsets = fallow_types::extract::compute_line_offsets(source);
    extract_flags(
        &parser_return.program,
        &line_offsets,
        extra_sdk_patterns,
        extra_env_prefixes,
        config_object_heuristics,
    )
}

#[cfg(all(test, not(miri)))]
mod tests {
    use super::*;
    use oxc_allocator::Allocator;
    use oxc_parser::Parser;
    use oxc_span::SourceType;

    fn extract_from_source(source: &str) -> Vec<FlagUse> {
        let allocator = Allocator::default();
        let parser_return = Parser::new(&allocator, source, SourceType::tsx()).parse();
        let line_offsets = fallow_types::extract::compute_line_offsets(source);
        extract_flags(&parser_return.program, &line_offsets, &[], &[], false)
    }

    fn extract_with_config_objects(source: &str) -> Vec<FlagUse> {
        let allocator = Allocator::default();
        let parser_return = Parser::new(&allocator, source, SourceType::tsx()).parse();
        let line_offsets = fallow_types::extract::compute_line_offsets(source);
        extract_flags(&parser_return.program, &line_offsets, &[], &[], true)
    }

    #[test]
    fn detects_process_env_feature_flag() {
        let flags = extract_from_source("if (process.env.FEATURE_NEW_CHECKOUT) { doStuff(); }");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "FEATURE_NEW_CHECKOUT");
        assert_eq!(flags[0].kind, FlagUseKind::EnvVar);
        assert!(flags[0].guard_span_start.is_some());
    }

    #[test]
    fn detects_next_public_enable_prefix() {
        let flags = extract_from_source("if (process.env.NEXT_PUBLIC_ENABLE_BETA) {}");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "NEXT_PUBLIC_ENABLE_BETA");
    }

    #[test]
    fn ignores_non_flag_env_vars() {
        let flags = extract_from_source("const url = process.env.DATABASE_URL;");
        assert!(flags.is_empty());
    }

    #[test]
    fn detects_negated_env_flag() {
        let flags = extract_from_source("if (!process.env.FEATURE_X) { fallback(); }");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "FEATURE_X");
    }

    #[test]
    fn detects_launchdarkly_use_flag() {
        let flags = extract_from_source("const flag = useFlag('new-checkout');");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "new-checkout");
        assert_eq!(flags[0].kind, FlagUseKind::SdkCall);
        assert_eq!(flags[0].sdk_name.as_deref(), Some("LaunchDarkly"));
    }

    #[test]
    fn detects_statsig_use_gate() {
        let flags = extract_from_source("if (useGate('beta-feature')) {}");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "beta-feature");
        assert_eq!(flags[0].sdk_name.as_deref(), Some("Statsig"));
    }

    #[test]
    fn detects_unleash_is_enabled() {
        let flags = extract_from_source("client.isEnabled('feature-x')");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "feature-x");
    }

    #[test]
    fn detects_growthbook_get_feature_value() {
        let flags = extract_from_source("const val = getFeatureValue('parser', false);");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "parser");
        assert_eq!(flags[0].sdk_name.as_deref(), Some("GrowthBook"));
    }

    #[test]
    fn detects_posthog_hooks() {
        let flags = extract_from_source(
            "const enabled = useFeatureFlagEnabled('new-checkout');\n\
             const payload = useFeatureFlagPayload('checkout-copy');\n\
             const variant = useFeatureFlagVariantKey('pricing-test');",
        );

        let names: Vec<_> = flags.iter().map(|flag| flag.flag_name.as_str()).collect();
        assert_eq!(names, ["new-checkout", "checkout-copy", "pricing-test"]);
        assert!(
            flags
                .iter()
                .all(|flag| flag.sdk_name.as_deref() == Some("PostHog"))
        );
    }

    #[test]
    fn detects_vercel_flags_object_key_and_core_evaluate_from_imports() {
        let flags = extract_from_source(
            "import { flag, evaluate as evalFlag } from 'flags/next';\n\
             export const showSale = flag({ key: 'summer-sale', decide: () => false });\n\
             const value = await evalFlag('show-new-feature', false);",
        );

        let names: Vec<_> = flags.iter().map(|flag| flag.flag_name.as_str()).collect();
        assert_eq!(names, ["summer-sale", "show-new-feature"]);
        assert!(
            flags
                .iter()
                .all(|flag| flag.sdk_name.as_deref() == Some("Vercel Flags"))
        );
    }

    #[test]
    fn detects_vercel_flags_namespace_imports() {
        let flags = extract_from_source(
            "import * as vercelFlags from '@vercel/flags';\n\
             const value = await vercelFlags.evaluate('show-new-feature', false);\n\
             export const showSale = vercelFlags.flag({ key: 'summer-sale', decide: () => false });",
        );

        let names: Vec<_> = flags.iter().map(|flag| flag.flag_name.as_str()).collect();
        assert_eq!(names, ["show-new-feature", "summer-sale"]);
        assert!(
            flags
                .iter()
                .all(|flag| flag.sdk_name.as_deref() == Some("Vercel Flags"))
        );
    }

    #[test]
    fn detects_vercel_flags_calls_before_import_declaration() {
        let flags = extract_from_source(
            "export const showSale = flag({ key: 'summer-sale', decide: () => false });\n\
             import { flag } from 'flags/next';",
        );

        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "summer-sale");
        assert_eq!(flags[0].sdk_name.as_deref(), Some("Vercel Flags"));
    }

    #[test]
    fn ignores_unimported_vercel_like_function_names() {
        let flags = extract_from_source(
            "function math() { return evaluate('2 + 2'); }\n\
             function marker() { return flag({ key: 'ui-row' }); }",
        );

        assert!(flags.is_empty());
    }

    #[test]
    fn detects_configcat_detail_evaluation() {
        let flags = extract_from_source(
            "const details = await client.getValueDetailsAsync('new-checkout', false);",
        );
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "new-checkout");
        assert_eq!(flags[0].sdk_name.as_deref(), Some("ConfigCat"));
    }

    #[test]
    fn detects_optimizely_decisions_and_variables() {
        let flags = extract_from_source(
            "const [decision] = useDecision('checkout-flow');\n\
             const copy = optimizelyClient.getFeatureVariableString('checkout-flow', 'copy', userId, attrs);\n\
             const json = optimizelyClient.getFeatureVariableJson('checkout-flow', 'json', userId, attrs);",
        );

        assert_eq!(flags.len(), 3);
        assert!(flags.iter().all(|flag| flag.flag_name == "checkout-flow"));
        assert!(
            flags
                .iter()
                .all(|flag| flag.sdk_name.as_deref() == Some("Optimizely"))
        );
    }

    #[test]
    fn detects_eppo_typed_assignments() {
        let flags = extract_from_source(
            "const value = client.getBooleanAssignment('new-onboarding', subject, {}, false);\n\
             const details = client.getStringAssignmentDetails('copy-test', subject, {}, 'control');\n\
             const payload = client.getJSONAssignmentDetails('payload-test', subject, {}, {});",
        );

        let names: Vec<_> = flags.iter().map(|flag| flag.flag_name.as_str()).collect();
        assert_eq!(names, ["new-onboarding", "copy-test", "payload-test"]);
        assert!(
            flags
                .iter()
                .all(|flag| flag.sdk_name.as_deref() == Some("Eppo"))
        );
    }

    #[test]
    fn ignores_sdk_call_without_string_arg() {
        let flags = extract_from_source("useFlag(dynamicKey);");
        assert!(flags.is_empty());
    }

    #[test]
    fn config_objects_off_by_default() {
        let flags = extract_from_source("if (config.features.newCheckout) {}");
        assert!(flags.is_empty());
    }

    #[test]
    fn detects_config_features_when_enabled() {
        let flags = extract_with_config_objects("if (config.features.newCheckout) {}");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "features.newCheckout");
        assert_eq!(flags[0].kind, FlagUseKind::ConfigObject);
    }

    #[test]
    fn detects_flags_object() {
        let flags = extract_with_config_objects("if (flags.enableV2) {}");
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "flags.enableV2");
    }

    #[test]
    fn ignores_non_flag_config_object() {
        let flags = extract_with_config_objects("const host = config.database.host;");
        assert!(flags.is_empty());
    }

    #[test]
    fn captures_if_guard_span() {
        let source = "if (process.env.FEATURE_X) {\n  doStuff();\n}";
        let flags = extract_from_source(source);
        assert_eq!(flags.len(), 1);
        assert!(flags[0].guard_span_start.is_some());
        assert!(flags[0].guard_span_end.is_some());
    }

    #[test]
    fn captures_ternary_guard_span() {
        let source = "const x = useFlag('beta') ? newFlow() : oldFlow();";
        let flags = extract_from_source(source);
        assert_eq!(flags.len(), 1);
        assert!(flags[0].guard_span_start.is_some());
    }

    #[test]
    fn detects_custom_sdk_pattern() {
        let allocator = Allocator::default();
        let source = "isFeatureActive('my-flag');";
        let parser_return = Parser::new(&allocator, source, SourceType::tsx()).parse();
        let line_offsets = fallow_types::extract::compute_line_offsets(source);
        let custom = vec![("isFeatureActive".to_string(), 0, "Internal".to_string())];
        let flags = extract_flags(&parser_return.program, &line_offsets, &custom, &[], false);
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "my-flag");
        assert_eq!(flags[0].sdk_name.as_deref(), Some("Internal"));
    }

    #[test]
    fn custom_sdk_pattern_can_use_vercel_object_function_name() {
        let allocator = Allocator::default();
        let source = "flag('internal-flag');";
        let parser_return = Parser::new(&allocator, source, SourceType::tsx()).parse();
        let line_offsets = fallow_types::extract::compute_line_offsets(source);
        let custom = vec![("flag".to_string(), 0, "Internal".to_string())];
        let flags = extract_flags(&parser_return.program, &line_offsets, &custom, &[], false);
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "internal-flag");
        assert_eq!(flags[0].sdk_name.as_deref(), Some("Internal"));
    }

    #[test]
    fn detects_custom_env_prefix() {
        let allocator = Allocator::default();
        let source = "if (process.env.MYAPP_ENABLE_V2) {}";
        let parser_return = Parser::new(&allocator, source, SourceType::tsx()).parse();
        let line_offsets = fallow_types::extract::compute_line_offsets(source);
        let custom_prefixes = vec!["MYAPP_ENABLE_".to_string()];
        let flags = extract_flags(
            &parser_return.program,
            &line_offsets,
            &[],
            &custom_prefixes,
            false,
        );
        assert_eq!(flags.len(), 1);
        assert_eq!(flags[0].flag_name, "MYAPP_ENABLE_V2");
    }

    #[test]
    fn builtin_sdk_providers_are_distinct_and_ordered() {
        let providers = builtin_sdk_providers();
        assert!(!providers.is_empty());
        let mut sorted = providers.clone();
        sorted.sort_unstable();
        sorted.dedup();
        assert_eq!(
            sorted.len(),
            providers.len(),
            "providers must be distinct: {providers:?}"
        );
        assert!(
            !providers.contains(&""),
            "empty provider labels must not leak into the surfaced list"
        );
        assert_eq!(providers.first(), Some(&"LaunchDarkly"));
        assert_eq!(providers.last(), Some(&VERCEL_FLAGS_PROVIDER));
    }

    #[test]
    fn builtin_env_prefixes_match_source_constant() {
        let prefixes = builtin_env_prefixes();
        assert_eq!(prefixes, BUILTIN_ENV_PREFIXES);
        assert!(prefixes.contains(&"FEATURE_"));
        assert!(prefixes.contains(&"TOGGLE_"));
    }
}