pass CODEQL_FEATURE_RAM_2023 to the CLI

This prepares for an upcoming change in how the `--ram` argument to
the CLI is interpreted.

The CLI will interpret _either_ this feature flag _or_ an Action
version of 2.22.10 or earlier as a sign that it would fall back to
the current interpretation of `--ram`.

Later in the future, the Action can start using a less conservative
calculation of `--ram` (when it detect the CLI is sufficiently new
CLIs) and signal that to the CLI by _not_ passing
`CODEQL_FEATURE_RAM_2023` anyway.

That way we can avoid wrong RAM settings caused by mismatched CLI and
Actions versions.

src/environment.ts

@@ -29,6 +29,13 @@ export enum EnvVar {
   /** Whether the CodeQL Action will upload SARIF, not the CLI. */
   FEATURE_WILL_UPLOAD = "CODEQL_ACTION_FEATURE_WILL_UPLOAD",
 
+  /**
+   * This flag tells `codeql database analyze` that the `--ram` option it gets is still
+   * computed by the 2023 algorithm that leaves space for overshooting.
+   * The CLI will _implicitly_ treat this flag as set if the Action version is 2.22.10 or earlier.
+   */
+  FEATURE_RAM_2023 = "CODEQL_ACTION_FEATURE_RAM_2023",
+
   /** Whether the CodeQL Action has already warned the user about low disk space. */
   HAS_WARNED_ABOUT_DISK_SPACE = "CODEQL_ACTION_HAS_WARNED_ABOUT_DISK_SPACE",
 

src/util.ts

@@ -161,6 +161,16 @@ export async function withTmpDir<T>(
  * when the user doesn't explicitly specify a memory setting.
  * This is a heuristic to avoid OOM errors (exit code 137 / SIGKILL)
  * from committing too much of the available memory to CodeQL.
+ *
+ * BEWARE: Eventually, with new enough CLIs, this computation can be made
+ * less conservative, because the CLI can now itself reserve space for memory
+ * overhead of the JVM. When this happens, stop passing FEATURE_RAM_2023
+ * feature variable.
+ *
+ * Also this rewrite cannot happen until the Action version is strictly above
+ * 2.22.10, because the CLI will interpret a version of 2.22.10 or lower as
+ * "old action that does not yet know to pass FEATURE_RAM_2023".
+ *
  * @returns number
  */
 function getSystemReservedMemoryMegaBytes(
@@ -539,6 +549,7 @@ export function initializeEnvironment(version: string) {
   core.exportVariable(String(EnvVar.FEATURE_SANDWICH), "false");
   core.exportVariable(String(EnvVar.FEATURE_SARIF_COMBINE), "true");
   core.exportVariable(String(EnvVar.FEATURE_WILL_UPLOAD), "true");
+  core.exportVariable(String(EnvVar.FEATURE_RAM_2023), "true");
   core.exportVariable(String(EnvVar.VERSION), version);
 }