github
diff --git a/‎lib/dependency-caching.js
Lines changed: 7 additions & 1 deletion b/‎lib/dependency-caching.js
Lines changed: 7 additions & 1 deletion
diff --git a/‎lib/dependency-caching.js.map
Lines changed: 1 addition & 1 deletion b/‎lib/dependency-caching.js.map
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diff --git a/‎lib/environment.js
Lines changed: 5 additions & 0 deletions b/‎lib/environment.js
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diff --git a/‎lib/environment.js.map
Lines changed: 1 addition & 1 deletion b/‎lib/environment.js.map
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diff --git a/‎src/dependency-caching.ts
Lines changed: 9 additions & 1 deletion b/‎src/dependency-caching.ts
Lines changed: 9 additions & 1 deletion
diff --git a/‎src/environment.ts
Lines changed: 6 additions & 0 deletions b/‎src/environment.ts
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@@ -9,6 +9,7 @@ import { Config } from "./config-utils";
 import { Language } from "./languages";
 import { Logger } from "./logging";
 import { getRequiredEnvParam } from "./util";
+import { EnvVar } from "./environment";
 
 /**
  * Caching configuration for a particular language.
@@ -199,5 +200,12 @@ async function cacheKey(
  */
 async function cachePrefix(language: Language): Promise<string> {
   const runnerOs = getRequiredEnvParam("RUNNER_OS");
-  return `${CODEQL_DEPENDENCY_CACHE_PREFIX}-${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
+  const customPrefix = process.env[EnvVar.DEPENDENCY_CACHING_PREFIX];
+  let prefix = CODEQL_DEPENDENCY_CACHE_PREFIX;
+
+  if (customPrefix !== undefined && customPrefix.length > 0) {
+    prefix = `${prefix}-${customPrefix}`;
+  }
+
+  return `${prefix}-${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
 }
@@ -105,4 +105,10 @@ export enum EnvVar {
    * change the inputs to the Action.
    */
   DEPENDENCY_CACHING = "CODEQL_ACTION_DEPENDENCY_CACHING",
+
+  /**
+   * An optional string to add into the cache key used by dependency caching.
+   * Useful for testing purposes where multiple caches may be stored in the same repository.
+   */
+  DEPENDENCY_CACHING_PREFIX = "CODEQL_ACTION_DEPENDENCY_CACHE_PREFIX",
 }