@fgv/ts-res


A TypeScript library for multidimensional resource management with internationalization and localization support. @fgv/ts-res provides a sophisticated system for managing resources with complex conditional logic based on qualifiers like language, territory, and custom dimensions.

Understanding the Resource Model

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In @fgv/ts-res, a resource represents a logical entity (like a user profile form, API configuration, or UI component) that can vary based on context. Instead of simple key-value pairs, resources are composed of candidates - each providing a full or partial representation of that entity for various different contexts.

The context is represented as a configurable set of typed qualifiers with some value. Each candidate has an associated condition set consisting of zero or more conditions, each of which specifies some qualifier and a value to be matched. Qualifiers not present in a condition set are irrelevant, so the empty condition set is unconditional and matches any context.

``typescript
// Traditional i18n approach - separate keys, full duplication
{
"profile.title.en": "User Profile",
"profile.title.fr": "Profil Utilisateur",
"profile.button.en": "Save Changes",
"profile.button.fr": "Enregistrer les Modifications",
"profile.title.en-CA": "User Profile", // Duplicated!
"profile.button.en-CA": "Save Changes" // Duplicated!
}

// ts-res approach - one resource, multiple candidates
{
"id": "user.profile",
"candidates": [
{
"json": { "title": "User Profile", "button": "Save Changes" },
"conditions": { "language": "en" }
},
{
"json": { "title": "Profil Utilisateur", "button": "Enregistrer" },
"conditions": { "language": "fr" }
},
{
"json": { "button": "Save Eh!" }, // Only override button text
"conditions": { "language": "en", "territory": "CA" }
}
]
}
`

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It is possible that several candidates for some resource will match any given context, which enables composition of partial candidates - you don't need to duplicate entire resources, just specify what changes:

`typescript
// Base configuration for all environments
{
"id": "api.config",
"candidates": [
{
"json": {
"timeout": 5000,
"retries": 3,
"features": { "analytics": true, "debugging": false }
},
"conditions": {} // Base case - applies everywhere
},
{
"json": {
"url": "https://api.production.com",
"features": { "debugging": false }
},
"conditions": { "environment": "production" }
},
{
"json": {
"url": "https://api.dev.com",
"features": { "debugging": true } // Only override debugging
},
"conditions": { "environment": "development" }
}
]
}
`

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1. Single Best Match - Pick the most specific candidate only:
`typescript
// Context: { environment: "development" }
const bestMatch = resolver.resolveBestResourceCandidate('api.config').orThrow();
console.log(bestMatch.candidate.json);
// Returns: { "url": "api.dev.com", "features": { "debugging": true } }
// Note: Only the development candidate, not merged with base
`

2. All Matching Candidates - Get everything that matches for analysis:
`typescript
const allMatches = resolver.resolveAllCandidates('api.config').orThrow();
// Returns array: [base candidate, development candidate]
// Each candidate as separate objects, not merged
`

3. Composed Resolution - Merge all matching candidates in priority order:
`typescript
// Context: { language: "en", territory: "CA", userType: "admin" }
const composed = resolver.resolveComposedResourceValue('user.dashboard').orThrow();
console.log(composed);
// Returns merged result: {
// title: 'Dashboard', // from base English
// nav: { home: 'Home', settings: 'Preferences' }, // base + Canadian override
// actions: {
// save: 'Save, eh!', // from Canadian variant
// cancel: 'Cancel', // from base English
// admin: 'Admin Panel' // from admin variant
// }
// }
`

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Eliminates Duplication: Change base configuration once, variants inherit automatically

Handles Complexity: Easily manage overlapping conditions (Canadian English admin users vs regular Canadian English users)

Maintainable: Add new dimensions (user types, themes, devices) without restructuring existing resources

Flexible: Same resource system handles i18n, configuration management, feature flags, and more

Installation

`bash
npm install @fgv/ts-res
`

Quick Start

This example demonstrates all three resolution strategies using a user dashboard that varies by language, region, and user type:

`typescript
import * as TsRes from '@fgv/ts-res';

// 1. Create a resource manager using predefined configuration
const manager = TsRes.Resources.ResourceManagerBuilder.createPredefined('default').orThrow();

// 2. Add a resource with base + partial candidates
manager.addResource({
id: 'user.dashboard',
resourceTypeName: 'json',
candidates: [
// Base English dashboard
{
json: {
title: 'Dashboard',
nav: { home: 'Home', settings: 'Settings' },
actions: { save: 'Save', cancel: 'Cancel' }
},
conditions: { language: 'en' }
},
// Canadian English - only changes some terminology
{
json: {
nav: { settings: 'Preferences' }, // Only override this
actions: { save: 'Save, eh!' } // And this
},
conditions: { language: 'en', territory: 'CA' }
},
// Admin users get additional actions
{
json: {
actions: {
save: 'Save',
cancel: 'Cancel',
admin: 'Admin Panel' // Additional action
}
},
conditions: { userType: 'admin' }
}
]
}).orThrow();

// 3. Build the resource manager to prepare for resolution
manager.build().orThrow();

// 4. Create resolver and demonstrate different resolution strategies
const resolver = TsRes.ResourceResolver.create(manager).orThrow();

// Canadian admin user context
const contextualResolver = resolver.withContext({
language: 'en',
territory: 'CA',
userType: 'admin'
}).orThrow();

// COMPOSED RESOLUTION - Merges base + Canadian + admin candidates
const composed = contextualResolver.resolveComposedResourceValue('user.dashboard').orThrow();
console.log(composed);
// Result: {
// title: 'Dashboard', // from base English
// nav: { home: 'Home', settings: 'Preferences' }, // base + Canadian override
// actions: {
// save: 'Save, eh!', // from Canadian variant
// cancel: 'Cancel', // from base English
// admin: 'Admin Panel' // from admin variant
// }
// }

// SINGLE BEST MATCH - Get most specific candidate only
const bestMatch = contextualResolver.resolveBestResourceCandidate('user.dashboard').orThrow();
console.log(bestMatch.candidate.json);
// Returns just the admin candidate (most specific match)

// ALL MATCHES - Get all matching candidates for analysis
const allMatches = contextualResolver.resolveAllCandidates('user.dashboard').orThrow();
console.log(Found ${allMatches.length} matching candidates);
// Returns array: [base English, Canadian English, admin]
`

Features

- Composed Resource Resolution: Merge multiple partial candidates into complete resources
- Multidimensional Qualifiers: Organize by language, territory, user types, environments, and custom dimensions
- Flexible Resolution Strategies: Single best match, all matches, or composed resolution
- Type-Safe: Full TypeScript support with comprehensive type definitions
- Partial Candidate Support: Override only what changes, inherit the rest
- Priority-Based Matching: Configurable priority levels for different qualifiers
- Resource Merging: Support for augmenting and replacing merge strategies
- File System Integration: Import resources from file systems with automatic condition inference
- Context Filtering: Generate clean environment-specific bundles
- BCP47 Language Support: Built-in support for BCP47 language tags
- Extensible Architecture: Plugin-based system for custom qualifier types

Technical Concepts

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Qualifiers define the dimensions along which resources can vary:

`typescript
// Built-in qualifiers
- language: 'en', 'fr', 'en-CA' // BCP47 language tags
- territory: 'US', 'CA', 'FR' // Geographic regions
- currentTerritory: 'US' // User's current location

// Custom qualifiers
- userType: 'admin', 'user', 'guest'
- environment: 'dev', 'staging', 'prod'
- theme: 'light', 'dark'
- device: 'mobile', 'tablet', 'desktop'
`

Conditions specify when a candidate applies using qualifier-value pairs:

`typescript
{
language: 'en-CA', // Canadian English
territory: 'CA', // Canada
userType: 'admin' // Admin users only
}
`

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Step 1: Individual Condition Scoring
Each condition is evaluated against the context to produce a score between 0.0 (NoMatch) and 1.0 (PerfectMatch):

`typescript
// Language hierarchy matching
context: { language: "en-US" }
condition: { language: "en-US" } → 1.0 (PerfectMatch)
condition: { language: "en" } → 0.8 (partial match - more general)
condition: { language: "fr-FR" } → 0.0 (NoMatch)

// Context list priority (earlier positions beat later)
context: { languages: ["en-US", "fr-FR"] }
condition: { language: "en" } → matches first preference (higher score)
condition: { language: "fr-FR" } → matches second preference (lower score)

// Territory/literal hierarchies can also produce partial matches
`

Step 2: Condition Set Evaluation
A candidate's condition set matches only if ALL conditions score > 0.0. If any condition yields NoMatch (0.0), the entire candidate is eliminated.

Step 3: Priority-First Ranking
Each qualifier has a default priority that its conditions inherit. Candidates are ranked using a priority-first system:

1. Primary rule: Candidate with the highest priority condition ALWAYS wins
2. Secondary rule: Score is only used as tie-breaker when priorities are equal
3. Comparison: Sort conditions within each candidate by (priority DESC, score DESC), then compare candidates pairwise

`typescript
// Context: { language: "en-CA", territory: "CA" }

// Example: Language (priority 600) beats Territory (priority 400)
Candidate A: { language: "en" } → priority 600, score 0.8 (partial match with en-CA)
Candidate B: { territory: "CA" } → priority 400, score 1.0 (perfect match)
// Winner: Candidate A (higher priority wins despite lower score)

// When priorities match, score breaks ties
Candidate A: { language: "en-CA" } → priority 600, score 1.0 (perfect match)
Candidate B: { language: "en" } → priority 600, score 0.8 (partial match)
// Winner: Candidate A (same priority, higher score)

// Multiple conditions: ALL must match, highest priority condition determines rank
Candidate C: { language: "en", territory: "CA" } → both conditions match
// Conditions: language (priority 600, score 0.8), territory (priority 400, score 1.0)
// Candidate rank determined by highest: priority 600, score 0.8
`

Step 4: Fallback Resolution (when no candidates match)
If no candidates pass Step 2 (all are eliminated by NoMatch conditions), the system falls back to resolution considering defaults:

`typescript
// Qualifier configured with default language = "en-US"
// Context: { language: "de-DE" } (German - no candidates match)

// During fallback, NoMatch conditions get promoted to their scoreAsDefault:
condition: { language: "en-US" } → scoreAsDefault = 1.0 (perfect match with default)
condition: { language: "fr-FR" } → scoreAsDefault = 0.0 (no match with default)
condition: { language: "en-GB" } → scoreAsDefault = 0.7 (partial match with default)

// Now English candidates become available for German users as intelligent fallbacks
`

The scoreAsDefault is automatically calculated when creating conditions by comparing the condition's value against the qualifier's configured default value using the same 0.0-1.0 scoring logic.

Step 5: Resolution Strategy Application

- Single Best Match: Return the top-ranked candidate only
- All Candidates: Return all candidates that passed matching (Step 2 or fallback Step 4), with their rankings
- Composed Resolution: Merge all matching candidates in rank order (lowest rank merged first, highest rank applied last)

Creating Resources

The most flexible and maintainable way to manage resources is through filesystem import, which automatically infers conditions and resource IDs from your directory structure.

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Organize your resources in a directory structure that reflects their conditions. Since values like "CA" or "FR" could be either language or territory, use explicit qualifiers or tokens:

`
resources/
├── language=en/ # language: "en"
│ ├── dashboard.json # id: "dashboard"
│ ├── profile.json # id: "profile"
│ └── territory=CA/ # language: "en", territory: "CA"
│ └── dashboard.json # id: "dashboard" (Canadian override)
├── language=fr/ # language: "fr"
│ ├── dashboard.json # id: "dashboard"
│ └── territory=CA/ # language: "fr", territory: "CA"
│ └── dashboard.json # id: "dashboard" (Quebec variant)
└── _resources.json # Resource collection or configuration
`

Or with tokens configured for brevity:

`
resources/
├── lang=en/ # language: "en" (using token)
│ ├── dashboard.json
│ └── terr=CA/ # territory: "CA" (using token)
│ └── dashboard.json
├── lang=fr/ # language: "fr" (using token)
│ └── terr=CA/ # territory: "CA" (using token)
│ └── dashboard.json
└── resources-config.json # Configuration with token definitions
`

Import resources with automatic context inference:

`typescript
import * as TsRes from '@fgv/ts-res';

// Create configuration with tokens for cleaner folder names
const config = TsRes.Config.SystemConfiguration.create({
name: 'my-app',
qualifierTypes: [
TsRes.QualifierTypes.LanguageQualifierType.create().orThrow(),
TsRes.QualifierTypes.TerritoryQualifierType.create().orThrow()
],
qualifiers: [
{ name: 'language', typeName: 'language', defaultPriority: 600, token: 'lang' },
{ name: 'territory', typeName: 'territory', defaultPriority: 400, token: 'terr' }
],
resourceTypes: [
TsRes.ResourceTypes.JsonResourceType.create().orThrow()
]
}).orThrow();

const manager = TsRes.Resources.ResourceManagerBuilder.create(config).orThrow();

// Import from filesystem - conditions are inferred from folder names
const importManager = TsRes.Import.ImportManager.create({
filetree: fileTree,
resources: manager,
importers: TsRes.Import.ImportManager.getDefaultImporters(),
initialContext: TsRes.Import.ImportContext.create().orThrow()
}).orThrow();

const result = importManager.importFromFileSystem({
type: 'path',
path: './resources'
}).orThrow();

// Result: All resources loaded with appropriate conditions
// - resources/lang=en/dashboard.json → { language: "en" }
// - resources/lang=en/terr=CA/dashboard.json → { language: "en", territory: "CA" }
`

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Resources can be stored in two formats:

1. Resource Collection Format (_resources.json):

Resource collections are flexible containers that can include:
- Loose resources: Complete resources with their candidates
- Loose candidates: Additional candidates to merge with existing resources
- Nested collections: Collections within collections for organization

`json
{
"resources": [
{
"id": "dashboard",
"candidates": [
{
"json": { "title": "Dashboard", "welcome": "Welcome!" },
"conditions": { "language": "en" }
}
]
}
],
"candidates": [
{
"resourceId": "dashboard",
"json": { "welcome": "Welcome, eh!" },
"conditions": { "language": "en", "territory": "CA" }
},
{
"resourceId": "profile",
"json": { "title": "User Profile" },
"conditions": { "language": "en" }
}
],
"collections": [
{
"name": "legal",
"resources": [
{
"id": "legal.privacy",
"candidates": [
{
"json": { "url": "/privacy.html" },
"conditions": {}
}
]
}
]
}
]
}
`

The importer merges all these elements:
- Loose candidates are added to their target resources
- Nested collections are flattened with appropriate ID prefixing
- Multiple candidates for the same resource are merged

2. Resource Tree Format (individual JSON files):
`json
// resources/en/dashboard.json
{
"title": "Dashboard",
"welcome": "Welcome!",
"nav": {
"home": "Home",
"settings": "Settings"
}
}

// resources/en/CA/dashboard.json (partial override)
{
"welcome": "Welcome, eh!",
"nav": {
"settings": "Preferences" // Canadian terminology
}
}
`

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The importer recognizes qualifier values in folder and file names using specific patterns:

1. Default Pattern: qualifier=value
`
resources/
├── language=en/ # { language: "en" }
├── language=fr-CA/ # { language: "fr-CA" }
├── territory=US/ # { territory: "US" }
└── environment=production/ # { environment: "production" }
`

2. Token Shorthand (when configured)
Qualifiers can define a "token" for brevity:
`typescript
// Configuration
{
qualifiers: [
{ name: "language", token: "lang" }, // Allow "lang=en"
{ name: "homeTerritory", token: "home" }, // Allow "home=US"
{ name: "environment", token: "env" } // Allow "env=prod"
]
}
`
`
resources/
├── lang=en-US/ # { language: "en-US" } via token
├── home=CA/ # { homeTerritory: "CA" } via token
└── env=production/ # { environment: "production" } via token
`

3. Optional Token Pattern (use with caution!)
When tokenIsOptional: true, the qualifier name/token can be omitted:
`typescript
{
qualifiers: [
{
name: "homeTerritory",
token: "home",
tokenIsOptional: true // DANGER: "CA" alone will match!
}
]
}
`
`
resources/
├── CA/ # { homeTerritory: "CA" } - matches without prefix!
├── home=US/ # { homeTerritory: "US" } - explicit still works
└── strings/ # Regular folder (if "strings" isn't a valid territory)
`

⚠️ Warning: Be very cautious with tokenIsOptional. If your qualifier accepts permissive values (like territories that could be any 2-letter code), ordinary folder names might be misinterpreted as qualifier values.

4. Context Accumulation
Nested folders inherit and combine parent conditions:
`
resources/
└── language=en/
└── territory=CA/
└── role=admin/ # { language: "en", territory: "CA", role: "admin" }
`

5. Resource ID Prefixing
Non-qualifier folders become part of the resource ID:
`
resources/
├── legal/ # Not a qualifier, becomes ID prefix
│ ├── privacy.json # id: "legal.privacy"
│ └── territory=EU/
│ └── privacy.json # id: "legal.privacy", conditions: { territory: "EU" }
└── language=fr/
└── legal/
└── privacy.json # id: "legal.privacy", conditions: { language: "fr" }
`

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For simple cases or dynamic resources, you can create them programmatically:

`typescript
manager.addResource({
id: 'api.config',
resourceTypeName: 'json',
candidates: [
{
json: { url: 'localhost:3000' },
conditions: { environment: 'development' }
},
{
json: { url: 'api.production.com' },
conditions: { environment: 'production' }
}
]
}).orThrow();
`

This is useful for configuration that changes based on deployment environment or resources generated at runtime.

Advanced Usage

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While priority and scoreAsDefault are typically determined automatically by qualifier configuration, they can be overridden for advanced use cases:

Use Case 1: Custom Priority for Territory-Based Content

For legal documents and branding, territory often matters more than language:

`typescript
// Configuration: Elevate territory priority for legal/brand content
const territoryPriorityConfig = TsRes.Config.SystemConfiguration.create({
name: 'territory-priority',
qualifierTypes: [
TsRes.QualifierTypes.LanguageQualifierType.create().orThrow(),
TsRes.QualifierTypes.TerritoryQualifierType.create().orThrow()
],
qualifiers: [
{ name: 'language', typeName: 'language', defaultPriority: 600 },
{ name: 'currentTerritory', typeName: 'territory', defaultPriority: 700 } // Higher than language
],
resourceTypes: [TsRes.ResourceTypes.JsonResourceType.create().orThrow()]
}).orThrow();

// Legal document with territory-specific versions
manager.addResource({
id: 'legal.privacy-policy',
candidates: [
{
json: { url: '/privacy-us.html' },
conditions: { currentTerritory: 'US' } // Priority 700
},
{
json: { url: '/privacy-ca.html' },
conditions: { currentTerritory: 'CA' } // Priority 700
},
{
json: { url: '/privacy-generic-fr.html' },
conditions: { language: 'fr' } // Priority 600 (lower)
}
]
}).orThrow();

// Context: { language: 'fr-CA', currentTerritory: 'CA' }
// Winner: Canadian privacy policy (territory priority 700 > language priority 600)
// Result: { url: '/privacy-ca.html' } - legally correct for Canada
`

Use Case 2: Custom scoreAsDefault for "Original Language" Scenarios

For content like quotes or historical documents, you might want to preserve the original language:

`typescript
// Configuration: Custom scoreAsDefault for originalLanguage qualifier
const originalLanguageConfig = TsRes.Config.SystemConfiguration.create({
name: 'preserve-original',
qualifierTypes: [
TsRes.QualifierTypes.LanguageQualifierType.create().orThrow()
],
qualifiers: [
{ name: 'language', typeName: 'language', defaultPriority: 600, defaultValue: 'en' },
{ name: 'originalLanguage', typeName: 'language', defaultPriority: 650, defaultValue: 'original' }
],
resourceTypes: [TsRes.ResourceTypes.JsonResourceType.create().orThrow()]
}).orThrow();

// Historical quote that should prefer original language
manager.addResource({
id: 'quotes.einstein',
candidates: [
{
json: { text: 'Gott würfelt nicht', attribution: 'Einstein, 1926' },
conditions: { originalLanguage: 'de' } // German original, scoreAsDefault = 1.0
},
{
json: { text: 'God does not play dice', attribution: 'Einstein, 1926' },
conditions: { language: 'en' } // English translation, scoreAsDefault = calculated from default
}
]
}).orThrow();

// Context: { language: 'fr' } (French user, no direct matches)
// Fallback resolution: originalLanguage='de' gets scoreAsDefault=1.0, language='en' gets lower score
// Winner: German original (higher scoreAsDefault in fallback resolution)
// Result: { text: 'Gott würfelt nicht', attribution: 'Einstein, 1926' }
`

These patterns ensure that content with special requirements (legal compliance, historical accuracy) gets appropriate priority treatment.

Individual Condition Overrides for Outlier Cases

For rare exceptions, you can override priority or scoreAsDefault directly in individual condition declarations without creating new configurations:

`typescript
// Most content uses standard language/territory priorities
// But this specific legal resource needs territory to take precedence

manager.addResource({
id: 'legal.gdpr-notice',
candidates: [
{
json: { text: 'GDPR applies', url: '/gdpr-eu.html' },
conditions: {
territory: {
qualifier: 'territory',
operator: 'eq',
value: 'EU',
priority: 700 // Override: higher than normal territory priority
}
}
},
{
json: { text: 'Generic privacy notice', url: '/privacy.html' },
conditions: { language: 'en' } // Uses default language priority (600)
}
]
}).orThrow();

// Individual scoreAsDefault override for a specific quote
manager.addResource({
id: 'quotes.shakespeare',
candidates: [
{
json: { text: 'To be or not to be', source: 'Hamlet' },
conditions: {
originalLanguage: {
qualifier: 'originalLanguage',
operator: 'eq',
value: 'en',
scoreAsDefault: 1.0 // Override: perfect fallback score for English original
}
}
}
]
}).orThrow();
`

This approach is more efficient than creating separate configurations when you only have occasional exceptions to the standard priority rules.

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`typescript
// Using the resource manager's builder for individual resources
const manager = TsRes.Resources.ResourceManagerBuilder.createPredefined('default').orThrow();

manager.addResource({
id: 'user.profile',
resourceTypeName: 'json',
candidates: [
{
json: { title: 'Profile', button: 'Edit' },
conditions: { language: 'en' }
},
{
json: { title: 'Profil', button: 'Modifier' },
conditions: { language: 'fr' }
}
]
}).orThrow();
`

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`typescript
// Create a resource manager and import from file system
const manager = TsRes.Resources.ResourceManagerBuilder.createPredefined('default').orThrow();

const importManager = TsRes.Import.ImportManager.create({
filetree: fileTree,
resources: manager,
importers: TsRes.Import.ImportManager.getDefaultImporters(),
initialContext: TsRes.Import.ImportContext.create().orThrow()
}).orThrow();

const importResult = importManager.importFromFileSystem({
type: 'path',
path: './resources'
}).orThrow();
`

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Resources support different merge strategies:

`typescript
{
id: 'app.config',
json: { apiUrl: 'https://api.example.com' },
conditions: { environment: 'production' },
mergeMethod: 'replace' // or 'augment' (default)
}
`

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`typescript
// Create a system configuration with custom qualifiers and types
const customConfig = TsRes.Config.SystemConfiguration.create({
name: 'custom-config',
description: 'Custom configuration with user types',
qualifierTypes: [
TsRes.QualifierTypes.LanguageQualifierType.create().orThrow(),
TsRes.QualifierTypes.LiteralQualifierType.create({
key: 'userType',
values: ['admin', 'user', 'guest'],
hierarchy: {
'admin': ['user', 'guest'],
'user': ['guest']
}
}).orThrow()
],
qualifiers: [
{ name: 'language', typeName: 'language', defaultPriority: 600 },
{ name: 'userType', typeName: 'userType', defaultPriority: 500 }
],
resourceTypes: [
TsRes.ResourceTypes.JsonResourceType.create().orThrow()
]
}).orThrow();

const manager = TsRes.Resources.ResourceManagerBuilder.create({
qualifiers: customConfig.qualifiers,
resourceTypes: customConfig.resourceTypes
}).orThrow();
`

API Reference

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- ResourceManagerBuilder: Central builder for resource management systems
- ResourceResolver: Runtime resolver for getting resources in specific contexts
- Resource: Individual resource with candidates for different contexts
- ResourceCandidate: Specific resource variant with conditions
- SystemConfiguration: Configuration defining qualifiers, types, and defaults
- Condition: Individual condition with qualifier, operator, and value
- ConditionSet: Collection of conditions for resource matching

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- Resources: Core resource management classes (ResourceManagerBuilder, etc.)
- Config: System configuration classes (SystemConfiguration, predefined configs)
- Qualifiers: Qualifier definition and management
- Conditions: Condition and condition set management
- QualifierTypes: Built-in and custom qualifier type definitions
- Context: Context definition for resource resolution
- Import: File system and external resource import utilities
- ResourceJson: JSON serialization and deserialization
- Bundle: Resource bundling and deployment utilities
- Runtime: Runtime resolution classes (ResourceResolver, etc.)

Context Filtering and Qualifier Reduction

One feature of ts-res is its ability to create filtered, context-specific resource bundles with reduced qualifiers. This is particularly useful for operational scenarios like feature flag management across different environments.

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Consider a feature flag system with different settings across environments:

`typescript
// Feature flags with environment-specific settings
const featureFlags = [
{
id: 'features.newDashboard',
json: { enabled: false, rolloutPercent: 0 },
conditions: { environment: 'production' }
},
{
id: 'features.newDashboard',
json: { enabled: true, rolloutPercent: 50 },
conditions: { environment: 'integration' }
},
{
id: 'features.newDashboard',
json: { enabled: true, rolloutPercent: 100 },
conditions: { environment: 'development' }
},
{
id: 'features.betaAPI',
json: { enabled: false, version: 'v1' },
conditions: { environment: 'production' }
},
{
id: 'features.betaAPI',
json: { enabled: true, version: 'v2' },
conditions: { environment: 'integration' }
},
{
id: 'features.betaAPI',
json: { enabled: true, version: 'v2-beta' },
conditions: { environment: 'development' }
}
];
`

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Without filtering, your complete bundle contains all environments:

`typescript
const completeBundle = resourceManager.getResourceCollectionDecl().orThrow();

// Result: All candidates with all environment conditions
{
"resources": [
{
"id": "features.newDashboard",
"candidates": [
{
"json": { "enabled": false, "rolloutPercent": 0 },
"conditions": { "environment": "production" }
},
{
"json": { "enabled": true, "rolloutPercent": 50 },
"conditions": { "environment": "integration" }
},
{
"json": { "enabled": true, "rolloutPercent": 100 },
"conditions": { "environment": "development" }
}
]
},
// ... more resources with similar environment conditions
]
}
`

Problem: Bundle contains all environments, making it difficult to compare environment-specific configurations.

$3

Filter for a specific environment (e.g., production):

`typescript
const resourceManager = TsRes.Resources.ResourceManagerBuilder.createPredefined('default').orThrow();
// ... add feature flag resources ...
resourceManager.build().orThrow();

const productionContext = resourceManager.validateContext({
environment: 'production'
}).orThrow();

const filteredBundle = resourceManager.getResourceCollectionDecl({
filterForContext: productionContext
// reduceQualifiers: false (default)
}).orThrow();

// Result: Only production candidates, but environment conditions remain
{
"resources": [
{
"id": "features.newDashboard",
"candidates": [
{
"json": { "enabled": false, "rolloutPercent": 0 },
"conditions": { "environment": "production" } // Environment condition still present
}
]
},
{
"id": "features.betaAPI",
"candidates": [
{
"json": { "enabled": false, "version": "v1" },
"conditions": { "environment": "production" } // Environment condition still present
}
]
}
]
}
`

Improvement: Bundle size reduced, but environment conditions add noise when comparing between environments.

$3

Filter for production AND reduce redundant qualifiers:

`typescript
const cleanProductionBundle = resourceManager.getResourceCollectionDecl({
filterForContext: productionContext,
reduceQualifiers: true // Enable qualifier reduction
}).orThrow();

// Result: Clean production bundle with environment conditions removed
{
"resources": [
{
"id": "features.newDashboard",
"candidates": [
{
"json": { "enabled": false, "rolloutPercent": 0 }
// conditions: {} - Environment condition removed!
}
]
},
{
"id": "features.betaAPI",
"candidates": [
{
"json": { "enabled": false, "version": "v1" }
// conditions: {} - Environment condition removed!
}
]
}
]
}
`

Benefits:
- Clean bundles: No irrelevant environment conditions
- Easy comparison: Compare bundles between environments to see actual differences
- Reduced noise: Focus on configuration values, not deployment context

$3

Now you can easily compare configuration differences between environments:

`typescript
// Get clean bundles for each environment
const [prodBundle, devBundle] = await Promise.all([
getCleanBundle('production'),
getCleanBundle('development')
]);

// Compare actual differences without environment noise
function compareFeatureFlags(prod, dev) {
prod.resources.forEach(prodResource => {
const devResource = dev.resources.find(r => r.id === prodResource.id);
const prodConfig = prodResource.candidates[0].json;
const devConfig = devResource.candidates[0].json;

if (JSON.stringify(prodConfig) !== JSON.stringify(devConfig)) {
console.log(${prodResource.id} differs:, {
production: prodConfig,
development: devConfig
});
}
});
}

// Output:
// features.newDashboard differs: {
// production: { enabled: false, rolloutPercent: 0 },
// development: { enabled: true, rolloutPercent: 100 }
// }
// features.betaAPI differs: {
// production: { enabled: false, version: 'v1' },
// development: { enabled: true, version: 'v2-beta' }
// }
`

$3

Qualifier reduction is intelligent - it only removes qualifiers that match perfectly across ALL filtered candidates:

`typescript
// Resource with environment + language conditions
const multiQualifierResource = {
id: 'features.localized',
candidates: [
{
json: { enabled: true, locale: 'en-US' },
conditions: { environment: 'production', language: 'en', territory: 'US' }
},
{
json: { enabled: true, locale: 'en-GB' },
conditions: { environment: 'production', language: 'en', territory: 'GB' }
},
{
json: { enabled: true, locale: 'fr-FR' },
conditions: { environment: 'production', language: 'fr', territory: 'FR' }
}
]
};

// Filter by environment only
const result = resource.toLooseResourceDecl({
filterForContext: { environment: 'production' },
reduceQualifiers: true
});

// Result: Environment reduced (all match 'production'), language/territory preserved (they differ)
{
"candidates": [
{
"json": { "enabled": true, "locale": "en-US" },
"conditions": { "language": "en", "territory": "US" } // environment removed, others preserved
},
{
"json": { "enabled": true, "locale": "en-GB" },
"conditions": { "language": "en", "territory": "GB" } // environment removed, others preserved
},
{
"json": { "enabled": true, "locale": "fr-FR" },
"conditions": { "language": "fr", "territory": "FR" } // environment removed, others preserved
}
]
}
`

$3

Feature Flag Management: Clean environment-specific bundles for operational analysis
Configuration Deployment: Environment-specific configs without deployment noise
A/B Testing: Clean experiment configurations for specific user segments
Internationalization: Language-specific bundles without region clutter
Multi-tenant Applications: Tenant-specific configurations without organizational context

Common Patterns

$3

`typescript
// Use predefined configuration or create custom one with territories
const manager = TsRes.Resources.ResourceManagerBuilder.createPredefined('territoryPriority').orThrow();

manager.addResource({
id: 'app.title',
resourceTypeName: 'json',
candidates: [
// Default English
{ json: { title: 'My App' }, conditions: { language: 'en' } },
// Canadian English variant
{ json: { title: 'My App, eh!' }, conditions: { language: 'en-CA' } },
// French
{ json: { title: 'Mon App' }, conditions: { language: 'fr' } }
]
}).orThrow();

manager.build().orThrow();

// Create resolver for Canadian user
const resolver = TsRes.ResourceResolver.create(manager).orThrow();
const canadianResolver = resolver.withContext({
language: 'en-CA',
currentTerritory: 'CA'
}).orThrow();

const title = canadianResolver.resolveComposedResourceValue('app.title').orThrow();
// Returns: { title: 'My App, eh!' }
`

$3

`typescript
// Create manager with custom environment qualifier
const manager = TsRes.Resources.ResourceManagerBuilder.createPredefined('default').orThrow();

manager.addResource({
id: 'api.config',
resourceTypeName: 'json',
candidates: [
{ json: { url: 'localhost:3000' }, conditions: { environment: 'development' } },
{ json: { url: 'api.staging.com' }, conditions: { environment: 'staging' } },
{ json: { url: 'api.production.com' }, conditions: { environment: 'production' } }
]
}).orThrow();

manager.build().orThrow();

// Resolve configuration for production
const resolver = TsRes.ResourceResolver.create(manager).orThrow();
const prodResolver = resolver.withContext({ environment: 'production' }).orThrow();
const config = prodResolver.resolveComposedResourceValue('api.config').orThrow();
// Returns: { url: 'api.production.com' }
`

Dependencies

- @fgv/ts-utils: Core utilities and Result pattern
- @fgv/ts-extras: Additional utility functions
- @fgv/ts-json-base: JSON validation and processing
- @fgv/ts-bcp47: BCP47 language tag processing
- @fgv/ts-json: JSON schema validation
- luxon: Date/time handling

Development

This library is part of a Rush monorepo. Development commands:

`bash


Install dependencies (from repository root)

rush install

Build the project

rushx build

Run tests

rushx test

Run tests with coverage

rushx coverage

Lint code

rushx lint

Fix linting issues

rushx fixlint

Generate API documentation

rushx build-docs

Build project and docs together

rushx build-all
``

License

MIT License. See LICENSE for details.

Contributing

Contributions are welcome! Please read the contributing guidelines and submit pull requests to the main repository.

Support

For questions, issues, or feature requests, please visit the GitHub issues page.