fix: validate CLI numeric limits

Motivation:

sjsonnet accepted invalid numeric CLI limits for stack frames, trace cropping, and parser recursion depth. Non-positive stack limits created a broken runtime setting, negative trace limits behaved like an undocumented full-trace setting, and negative parser recursion depth reached the parser as Parsing exceeded maximum recursion depth of -1.

Modification:

Validate --max-stack >= 1, --max-trace >= 0, and --max-parser-recursion-depth >= 0 after CLI parsing and before constructing Settings. Add JVM CLI regression tests for invalid stack, trace, and parser-depth values, and preserve the boundary behavior that --max-trace 0 keeps a full trace and --max-parser-recursion-depth 0 still allows non-recursive expressions.

Result:

Invalid numeric CLI limits now fail before evaluation or parsing with user-facing CLI errors. Stack and trace behavior matches C++ jsonnet and go-jsonnet for shared flags, while the sjsonnet-specific parser-depth flag now rejects only the invalid negative range.

References:

C++ jsonnet cmd/jsonnet.cpp rejects --max-stack < 1 and --max-trace < 0.

go-jsonnet cmd/jsonnet/cmd.go rejects --max-stack < 1 and --max-trace < 0.

sjsonnet readme.md documents --max-parser-recursion-depth without a negative-value meaning.

Author: He-Pin

sjsonnet/src-jvm-native/sjsonnet/SjsonnetMainBase.scala

@@ -195,6 +195,21 @@ object SjsonnetMainBase {
           Left("ERROR: cannot use --no-trailing-newline with --yaml-stream")
         else Right(())
       }
+      _ <- {
+        if (config.maxStack < 1) Left(s"ERROR: invalid --max-stack value: ${config.maxStack}")
+        else Right(())
+      }
+      _ <- {
+        if (config.maxTrace < 0) Left(s"ERROR: invalid --max-trace value: ${config.maxTrace}")
+        else Right(())
+      }
+      _ <- {
+        if (config.maxParserRecursionDepth < 0)
+          Left(
+            s"ERROR: invalid --max-parser-recursion-depth value: ${config.maxParserRecursionDepth}"
+          )
+        else Right(())
+      }
       file <- Right(config.file)
       debugStats =
         if (config.debugStats.value) { val s = new DebugStats; statsToReport = s; s }

sjsonnet/test/src-jvm/sjsonnet/MainTests.scala

@@ -147,6 +147,47 @@ object MainTests extends TestSuite {
       assert(err.contains("Max stack frames exceeded."))
     }
 
+    test("maxStackRejectsNonPositiveValues") {
+      val (zeroRes, zeroOut, zeroErr) = runMain("--exec", "1", "--max-stack", "0")
+      assert(zeroRes == 1)
+      assert(zeroOut.isEmpty)
+      assert(zeroErr.contains("ERROR: invalid --max-stack value: 0"))
+      assert(!zeroErr.contains("Max stack frames exceeded."))
+
+      val (negativeRes, negativeOut, negativeErr) = runMain("--exec", "1", "--max-stack", "-1")
+      assert(negativeRes == 1)
+      assert(negativeOut.isEmpty)
+      assert(negativeErr.contains("ERROR: invalid --max-stack value: -1"))
+      assert(!negativeErr.contains("Max stack frames exceeded."))
+    }
+
+    test("maxTraceRejectsNegativeValues") {
+      val (res, out, err) = runMain("--exec", "error 'x'", "--max-trace", "-1")
+      assert(res == 1)
+      assert(out.isEmpty)
+      assert(err.contains("ERROR: invalid --max-trace value: -1"))
+      assert(!err.contains("sjsonnet.Error"))
+    }
+
+    test("maxParserRecursionDepthRejectsNegativeValues") {
+      val (res, out, err) = runMain("--exec", "1", "--max-parser-recursion-depth", "-1")
+      assert(res == 1)
+      assert(out.isEmpty)
+      assert(err.contains("ERROR: invalid --max-parser-recursion-depth value: -1"))
+      assert(!err.contains("Parsing exceeded maximum recursion depth of -1"))
+    }
+
+    test("maxParserRecursionDepthZeroAllowsNonRecursiveExpressions") {
+      val (res, out, err) = runMain("--exec", "1", "--max-parser-recursion-depth", "0")
+      assert((res, out, err) == ((0, "1\n", "")))
+
+      val (nestedRes, nestedOut, nestedErr) =
+        runMain("--exec", "[1]", "--max-parser-recursion-depth", "0")
+      assert(nestedRes == 1)
+      assert(nestedOut.isEmpty)
+      assert(nestedErr.contains("Parsing exceeded maximum recursion depth of 0"))
+    }
+
     test("maxStackDoesNotCountTailRecursiveCalls") {
       val (res, out, err) = runMain(
         "--exec",