Avoid running subsequent meta-level builds after reaching the desired meta-level in MillBuildBootstrap

integration/feature/meta-skip-compile/resources/build.mill

@@ -0,0 +1 @@
+CoMpIlAtIoNeRrOr

integration/feature/meta-skip-compile/src/MetaSkipCompile.scala

@@ -0,0 +1,27 @@
+package mill.integration
+
+import mill.testkit.UtestIntegrationTestSuite
+
+import utest._
+
+object MetaSkipCompile extends UtestIntegrationTestSuite {
+
+  val tests: Tests = Tests {
+    test("test") - integrationTest { tester =>
+      // Make sure that when we pass in --meta-level 1, we stop after
+      // evaluating that level of the meta-build and do not proceed further,
+      // such that compilation errors in the build.mill do not affect us
+      val result1 = tester.eval(("--meta-level", "1", "resolve", "_"))
+      assert(result1.isSuccess)
+
+      // Without --meta-level 1, we hit the compilation error
+      val result2 = tester.eval(("resolve", "_"))
+      assert(!result2.isSuccess)
+
+      // Remove compilation error makes non-meta-level commands work again
+      os.write.over(tester.workspacePath / "build.mill", "")
+      val result3 = tester.eval(("resolve", "_"))
+      assert(result3.isSuccess)
+    }
+  }
+}

runner/src/mill/runner/MillBuildBootstrap.scala

@@ -181,29 +181,20 @@ class MillBuildBootstrap(
           depth,
           actualBuildFileName = nestedState.buildFile
         )) { evaluator =>
-          if (depth != 0) {
-            val retState = processRunClasspath(
+          if (depth == requestedDepth) processFinalTargets(nestedState, rootModule, evaluator)
+          else if (depth <= requestedDepth) nestedState
+          else {
+            processRunClasspath(
               nestedState,
               rootModule,
               evaluator,
               prevFrameOpt,
               prevOuterFrameOpt
             )
-
-            if (retState.errorOpt.isEmpty && depth == requestedDepth) {
-              // TODO: print some message and indicate actual evaluated frame
-              val evalRet = processFinalTargets(nestedState, rootModule, evaluator)
-              if (evalRet.errorOpt.isEmpty) retState
-              else evalRet
-            } else
-              retState
-
-          } else {
-            processFinalTargets(nestedState, rootModule, evaluator)
           }
         }
       }
-    // println(s"-evaluateRec($depth) " + recRoot(projectRoot, depth))
+
     res
   }