From 582d141a000067aed6ded10779a2842c06020dba Mon Sep 17 00:00:00 2001
From: Yabo Hu <yabhu@microsoft.com>
Date: Sat, 8 Aug 2026 14:28:37 +1000
Subject: [PATCH] deep merge tspconfig

---
 packages/typespec-powershell/src/emitter.ts   | 33 +---------
 .../src/utils/configuration.ts                | 60 +++++++++++++++++++
 2 files changed, 62 insertions(+), 31 deletions(-)
 create mode 100644 packages/typespec-powershell/src/utils/configuration.ts

diff --git a/packages/typespec-powershell/src/emitter.ts b/packages/typespec-powershell/src/emitter.ts
index 995e1512bb..226e0dd1fe 100644
--- a/packages/typespec-powershell/src/emitter.ts
+++ b/packages/typespec-powershell/src/emitter.ts
@@ -1,5 +1,5 @@
 import { Program, EmitContext, listServices, emitFile, resolvePath } from "@typespec/compiler";
-import { serialize, deserialize } from '@azure-tools/codegen';
+import { serialize } from '@azure-tools/codegen';
 import { createSdkContext } from "@azure-tools/typespec-client-generator-core";
 // Following files finally should be imported from @autorest/powershell
 // import { ModelState } from "./powershell/utils/model-state.js";
@@ -7,37 +7,8 @@ import { createSdkContext } from "@azure-tools/typespec-client-generator-core";
 import { getClients } from "./utils/clientUtils.js";
 import { transformPwshModel } from "./convertor/convertor.js";
 import { PSOptions } from "./types/interfaces.js";
+import { loadConfiguration } from "./utils/configuration.js";
 import { generatePwshModule } from "@autorest/powershell";
-import { readFileSync } from "fs";
-import path from "path";
-import { fileURLToPath } from "url";
-
-// Function to recursively interpolate placeholders in an object
-function interpolatePlaceholders(obj: any, values: any) {
-  for (const key in obj) {
-    if (typeof obj[key] === 'string') {
-      obj[key] = obj[key].replace(/{([^}]+)}/g, (match: string, placeholder: string) => values[placeholder]);
-    } else if (typeof obj[key] === 'object') {
-      interpolatePlaceholders(obj[key], values);
-    }
-  }
-}
-
-//load configuration from configuration.md
-function loadConfiguration(emitterOptions: Record<string, any>): Record<string, any> {
-  const __filename = fileURLToPath(import.meta.url);
-  const __dirname = path.dirname(__filename);
-  const configPath = path.join(__dirname, '../../configuration.yaml');
-  const configuration = deserialize<Record<string, any>>(readFileSync(configPath, 'utf8'), configPath);
-  // Define the values for interpolation
-  const interpolationValues = {
-    'module-name': emitterOptions['module-name'] ?? configuration['module-name'],
-    'service-name': emitterOptions['service-name'] ?? configuration['service-name']
-  };
-  interpolatePlaceholders(configuration, interpolationValues);
-  // If there is overlap between the configuration and the emitter options, the emitter options will take precedence
-  return { ...configuration, ...emitterOptions };
-}
 
 export async function $onEmit(context: EmitContext) {
   const program: Program = context.program;
diff --git a/packages/typespec-powershell/src/utils/configuration.ts b/packages/typespec-powershell/src/utils/configuration.ts
new file mode 100644
index 0000000000..fd00fa9e90
--- /dev/null
+++ b/packages/typespec-powershell/src/utils/configuration.ts
@@ -0,0 +1,60 @@
+import { deserialize } from '@azure-tools/codegen';
+import { readFileSync } from "fs";
+import path from "path";
+import { fileURLToPath } from "url";
+
+function isPlainObject(value: any): value is Record<string, any> {
+  return value !== null && typeof value === 'object' && !Array.isArray(value);
+}
+
+// Recursively merges source into target. Plain objects merge by key; arrays,
+// primitives and null in source replace the target value. Inputs are not mutated.
+export function deepMerge(target: any, source: any): any {
+  if (!isPlainObject(target) || !isPlainObject(source)) {
+    return source === undefined ? target : source;
+  }
+
+  const result: Record<string, any> = { ...target };
+  for (const key of Object.keys(source)) {
+    const sourceValue = source[key];
+    if (sourceValue === undefined) {
+      continue;
+    }
+    result[key] = isPlainObject(result[key]) && isPlainObject(sourceValue)
+      ? deepMerge(result[key], sourceValue)
+      : sourceValue;
+  }
+  return result;
+}
+
+// Recursively interpolate {placeholder} tokens in string values.
+export function interpolatePlaceholders(obj: any, values: Record<string, any>): void {
+  for (const key in obj) {
+    if (typeof obj[key] === 'string') {
+      obj[key] = obj[key].replace(/{([^}]+)}/g, (match: string, placeholder: string) => values[placeholder]);
+    } else if (obj[key] !== null && typeof obj[key] === 'object') {
+      interpolatePlaceholders(obj[key], values);
+    }
+  }
+}
+
+// Load configuration.yaml and merge emitter options over it, with emitter
+// options taking precedence at every level of nested mappings.
+export function loadConfiguration(emitterOptions: Record<string, any>): Record<string, any> {
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const configPath = path.join(__dirname, '../../../configuration.yaml');
+  const configuration = deserialize<Record<string, any>>(readFileSync(configPath, 'utf8'), configPath);
+
+  // Emitter options take precedence over the defaults, merged recursively so
+  // partial nested mappings (e.g. metadata) keep unspecified defaults.
+  const merged = deepMerge(configuration, emitterOptions);
+
+  const interpolationValues = {
+    'module-name': merged['module-name'],
+    'service-name': merged['service-name']
+  };
+  interpolatePlaceholders(merged, interpolationValues);
+
+  return merged;
+}