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refactor(core): centralize prompt discovery in PromptLoader and cleanup AssertionEngine #44

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refactor(core): centralize prompt discovery in PromptLoader and cleanup AssertionEngine #44

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2deb5fb
feat: implement PromptLoader service for prioritized prompt resolutio…
silkiy Apr 20, 2026
7ed45a5
refactor: break down resolveAndLoad into smaller private methods for …
silkiy Apr 20, 2026
6609419
refactor: implement dedicated check methods to align with PR comments
silkiy Apr 20, 2026
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84 changes: 17 additions & 67 deletions packages/assertions/src/engine/AssertionEngine.ts
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Original file line number Diff line number Diff line change
@@ -1,19 +1,20 @@
import { EvaliphyError, EvaliphyErrorCode, logger } from '@evaliphy/core';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import { EvaliphyError, EvaliphyErrorCode } from '@evaliphy/core';
import type { BaseMatcher } from '../matchers/base/BaseMatcher.js';
import { PromptLoader } from '../promptManager/promptLoader.js';
import { PromptRenderer } from '../promptManager/promptRenderer.js';
import { assertionRegistry } from "../registry.js";
import { type AssertionContext, type AssertionResult } from './types.js';

export class AssertionEngine {
/**
* Runs the assertion logic, executing an LLM call if the matcher requires it.
*/
static async run(
matcher: BaseMatcher,
context: AssertionContext
): Promise<AssertionResult> {
const startTime = Date.now();
const { input, options, llmClient, config } = context;
const { input, options, llmClient } = context;

try {
matcher.validate(input);
Expand All @@ -33,7 +34,6 @@ export class AssertionEngine {
usage = response.llmUsages;
}


const threshold = options.threshold ?? 0.7;
const passed = score >= threshold;

Expand All @@ -58,6 +58,10 @@ export class AssertionEngine {
}
}

/**
* Prepares the LLM prompt and schema for the assertion.
* Centralizes prompt loading through PromptLoader.
*/
private static prepareLLMRequest(matcher: BaseMatcher, context: AssertionContext) {
const { input, config } = context;
const assertionDef = assertionRegistry[matcher.name];
Expand All @@ -69,75 +73,18 @@ export class AssertionEngine {
);
}

const loadedPrompt = this.loadPrompt(matcher.name, assertionDef, config);
// Call the centralized PromptLoader to handle path resolution and loading
const loadedPrompt = PromptLoader.resolveAndLoad(matcher.name, assertionDef, config);
const variables = this.prepareVariables(input);
const finalPrompt = PromptRenderer.render(loadedPrompt.template, variables, assertionDef);
const outputSchema = assertionDef.outputSchema.zodSchema as any;

return { finalPrompt, outputSchema };
}

private static loadPrompt(matcherName: string, assertionDef: any, config: any) {
const configDir = config.configFile ? path.dirname(config.configFile) : process.cwd();

// 1. Check for custom prompts directory from config
const customPromptsDir = config.llmAsJudgeConfig?.promptsDir
? path.resolve(configDir, config.llmAsJudgeConfig.promptsDir)
: null;

// 2. Check for default prompts directory in consumer's root (convention)
const localPromptsDir = path.join(process.cwd(), 'prompts');

// 3. SDK internal prompts directory
const __dirname = path.dirname(fileURLToPath(import.meta.url));

// Support both source (../../prompts) and bundled dist (./prompts)
const sdkPromptsDirSource = path.resolve(__dirname, '../../prompts');
const sdkPromptsDirDist = path.resolve(__dirname, './prompts');

const searchPaths = [
customPromptsDir ? path.join(customPromptsDir, `${matcherName}.md`) : null,
path.join(localPromptsDir, `${matcherName}.md`),
path.join(sdkPromptsDirDist, `${matcherName}.md`),
path.join(sdkPromptsDirSource, `${matcherName}.md`),
].filter(Boolean) as string[];

try {
// 1. Try custom prompts directory from config
if (customPromptsDir) {
const customPath = path.join(customPromptsDir, `${matcherName}.md`);
if (PromptLoader.exists(customPath)) {
return PromptLoader.load(customPath, assertionDef);
} else {
console.warn(`Custom prompt file not found at: ${customPath}. Falling back to defaults.`);
}
}

// 2. Try other search paths (local convention, SDK dist, SDK source)
const fallbackPaths = [
path.join(localPromptsDir, `${matcherName}.md`),
path.join(sdkPromptsDirDist, `${matcherName}.md`),
path.join(sdkPromptsDirSource, `${matcherName}.md`),
];

for (const promptPath of fallbackPaths) {
if (PromptLoader.exists(promptPath)) {
return PromptLoader.load(promptPath, assertionDef);
}
}

// If none found, try the primary SDK path one last time to trigger the standard error
return PromptLoader.load(path.join(sdkPromptsDirDist, `${matcherName}.md`), assertionDef);
} catch (error: any) {
throw new EvaliphyError(
EvaliphyErrorCode.PROMPT_LOAD_ERROR,
`Failed to load prompt for "${matcherName}": ${error.message}`,
'Check your prompt file formatting and variables.',
error
);
}
}

/**
* Prepares the variables for the prompt renderer.
*/
private static prepareVariables(input: any) {
return {
...Object.fromEntries(
Expand All @@ -149,6 +96,9 @@ export class AssertionEngine {
} as Record<string, string>;
}

/**
* Executes the actual LLM call using the provided client.
*/
private static async executeLLMCall(matcher: BaseMatcher, llmClient: any, prompt: string, schema: any) {
try {
return await llmClient.generateObject(prompt, schema);
Expand Down
91 changes: 85 additions & 6 deletions packages/assertions/src/promptManager/promptLoader.ts
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
import { EvaliphyError, EvaliphyErrorCode } from '@evaliphy/core';
import { EvaliphyError, EvaliphyErrorCode, logger } from '@evaliphy/core';
import fs from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import { AssertionDefinition } from "../registry.js";

export interface LoadedPrompt {
Expand All @@ -11,14 +13,96 @@
};
}

/**
* Service to handle centralized prompt searching and loading.
*/
export class PromptLoader {

@priyanshus priyanshus Apr 20, 2026

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Can we break this function further?

@silkiy silkiy Apr 20, 2026

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Good catch! I agree the previous function was doing too much. I've broken it down into smaller, single-responsibility private methods (checkUserConfig, checkSdkDist, and checkSdkSource) so resolvePromptPath just acts as a clean orchestrator now. Just pushed the update!

/**
* Main entry point to resolve and load a prompt.
*/
static resolveAndLoad(matcherName: string, assertion: AssertionDefinition, config: any): LoadedPrompt {
try {
const filePath = this.resolvePromptPath(matcherName, config);
return this.load(filePath, assertion);
} catch (error: any) {
if (error instanceof EvaliphyError) throw error;
throw new EvaliphyError(
EvaliphyErrorCode.PROMPT_LOAD_ERROR,
`Failed to load prompt for "${matcherName}": ${error.message}`,
'Check your prompt file formatting and variables.',
error
);
}
}

/**
* Orchestrates the discovery process using single-responsibility check methods.
*/
private static resolvePromptPath(matcherName: string, config: any): string {
const fileName = `${matcherName}.md`;

// 1. Check User Config (Priority 1)
const customPath = this.checkUserConfig(config, fileName);
if (customPath) return customPath;

// 2. Check SDK Dist (Fallback 1)
const distPath = this.checkSdkDist(fileName);
if (distPath) return distPath;

// 3. Check SDK Source (Fallback 2)
const sourcePath = this.checkSdkSource(fileName);
if (sourcePath) return sourcePath;

// Default return to Dist path if none found (to trigger FILE_NOT_FOUND error in load())
const __dirname = path.dirname(fileURLToPath(import.meta.url));
return path.resolve(__dirname, './prompts', fileName);
}

/**
* Priority 1: Check for custom prompts directory from user config.
*/
private static checkUserConfig(config: any, fileName: string): string | null {
const configDir = config.configFile ? path.dirname(config.configFile) : process.cwd();
const promptsDir = config.llmAsJudgeConfig?.promptsDir;

if (!promptsDir) return null;

const customPath = path.resolve(configDir, promptsDir, fileName);
if (this.exists(customPath)) {
return customPath;
}

logger.warn(`Custom prompt file not found at: ${customPath}. Falling back to defaults.`);
return null;
}

/**
* Fallback 1: Check for default prompts directory in bundled SDK (Dist).
*/
private static checkSdkDist(fileName: string): string | null {
const __dirname = path.dirname(fileURLToPath(import.meta.url));
const distPath = path.resolve(__dirname, './prompts', fileName);

return this.exists(distPath) ? distPath : null;
}

/**
* Fallback 2: Check for default prompts directory in SDK Source (for development).
*/
private static checkSdkSource(fileName: string): string | null {
const __dirname = path.dirname(fileURLToPath(import.meta.url));
const sourcePath = path.resolve(__dirname, '../../prompts', fileName);

return this.exists(sourcePath) ? sourcePath : null;
}

static exists(filePath: string): boolean {
return fs.existsSync(filePath);
}

static load(filePath: string, assertion: AssertionDefinition): LoadedPrompt {
if (!this.exists(filePath)) {
throw new EvaliphyError(

Check failure on line 105 in packages/assertions/src/promptManager/promptLoader.ts

View workflow job for this annotation

GitHub Actions / test

packages/assertions/tests/judge/promptLoader.test.ts > PromptLoader > resolveAndLoad > should fallback to Fallback 2: SDK Source if Dist fails 

EvaliphyError: Prompt file not found at: /home/runner/work/evaliphy/evaliphy/packages/assertions/src/promptManager/prompts/testMatcher.md
 ❯ Function.load packages/assertions/src/promptManager/promptLoader.ts:105:13
 ❯ Function.resolveAndLoad packages/assertions/src/promptManager/promptLoader.ts:26:19
 ❯ packages/assertions/tests/judge/promptLoader.test.ts:81:35

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯
Serialized Error: { code: 'FILE_NOT_FOUND', hint: undefined }
EvaliphyErrorCode.FILE_NOT_FOUND,
`Prompt file not found at: ${filePath}`
);
Expand Down Expand Up @@ -52,22 +136,19 @@
}
const frontmatter: any = {};

// Simple YAML-like parser for basic frontmatter
yamlStr.split('\n').forEach(line => {
const [key, ...rest] = line.split(':');
if (key && rest.length > 0) {
const value = rest.join(':').trim();
if (value === '') {
frontmatter[key.trim()] = [];
} else if (value.startsWith('-')) {
// Handle simple lists
const listKey = key.trim();
if (!frontmatter[listKey]) frontmatter[listKey] = [];
} else {
frontmatter[key.trim()] = value;
}
} else if (line.trim().startsWith('-')) {
// Continue list
const lastKey = Object.keys(frontmatter).pop();
if (lastKey && Array.isArray(frontmatter[lastKey])) {
frontmatter[lastKey].push(line.trim().substring(1).trim());
Expand All @@ -88,7 +169,6 @@
const declared = frontmatter.input_variables ?? [];
const usedInTemplate = this.extractTemplateVariables(template);

// check declared variables match what the assertion requires
const missingDeclared = required.filter(v => !declared.includes(v));
if (missingDeclared.length > 0) {
throw new EvaliphyError(
Expand All @@ -98,7 +178,6 @@
);
}

// check the template actually uses the variables it declares
const missingInTemplate = declared.filter((v: string) => !usedInTemplate.includes(v));
if (missingInTemplate.length > 0) {
throw new EvaliphyError(
Expand Down
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