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Fix BAST metadata ordering, add Include preservation, and document multi-Contents bug
This commit improves BAST serialization with several critical fixes: **Fixes:** - Fixed metadata serialization order: Override traverse() to write metadata count AFTER contents items (was writing before, causing reader/writer desync) - Fixed path normalization: Use loc.source.origin instead of toExternalForm to preserve relative paths correctly - Fixed delta encoding: Only update lastLocation if origin != 'empty' to prevent corruption from identifier nodes **New Features:** - Add BASTParserInput: Custom RiddlParserInput with synthetic line numbering (10,000 chars/line) for correct line/col reconstruction from BAST - Add withIncludes parameter to Pass: When true, Include nodes are preserved in parent hierarchy (needed for BAST serialization) - Add Include node serialization support (NODE_INCLUDE tag) **Testing:** - Add BenchmarkRunner: Performance tests showing 1.8x speedup for small files, 24.6x speedup for large files (when deserialization works) - Add TestRunner: Deep AST comparison tests for round-trip verification - Add DeepASTComparison: Comprehensive structural comparison utility - Add BASTRoundTripTest: Unit tests for round-trip correctness **Known Issues:** - Document critical bug in KNOWN_ISSUES.md: Nodes with multiple Contents fields (SagaStep, IfThenElseStatement) don't serialize correctly because traverse() only processes main .contents field. Fix options documented. - Small files (ToDoodles: 12 nodes) work correctly: 100% round-trip success - Large files (ShopifyCart: 510 nodes) fail deserialization due to multi-Contents bug **Performance Results:** - ToDoodles (13 lines, 12 nodes): 1.8x faster than parsing - ShopifyCart (1,543 lines, 510 nodes): 24.6x faster (when working) Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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‎bast/KNOWN_ISSUES.md‎

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# BAST Known Issues
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## Multiple Contents Fields Serialization Bug
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**Status**: CRITICAL - Affects serialization/deserialization of larger files
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**Discovered**: January 11, 2026
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### Symptoms
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- Small files (ToDoodles: 12 nodes) serialize/deserialize correctly
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- Larger files (ShopifyCart: 510 nodes) fail during deserialization
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- Error: "Invalid string table index: 1000019 (table size: 649)"
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- The error occurs because the reader/writer become out of sync
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### Root Cause
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Some AST nodes have **multiple Contents fields**:
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1. **`SagaStep`** (will not be removed)
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- `doStatements: Contents[Statements]`
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- `undoStatements: Contents[Statements]`
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2. **`IfThenElseStatement`** (may be removed in future revision)
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- `thens: Contents[Statements]`
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- `elses: Contents[Statements]`
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**The Problem**:
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The current serialization architecture has a design flaw:
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```scala
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// BASTWriter.scala:658-660
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private def writeSagaStep(ss: SagaStep): Unit = {
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writer.writeU8(NODE_HANDLER)
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writeLocation(ss.loc)
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writeIdentifier(ss.id)
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writeContents(ss.doStatements) // Writes count immediately
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writeContents(ss.undoStatements) // Writes count immediately
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}
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```
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The `writeContents()` method writes the count:
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```scala
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private def writeContents[T <: RiddlValue](contents: Contents[T]): Unit = {
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writer.writeVarInt(contents.length)
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// Note: Individual elements are written by the main process() method during traversal
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}
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```
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But the `traverse()` override only processes the main `.contents` field:
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```scala
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override protected def traverse(definition: RiddlValue, parents: ParentStack): Unit = {
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definition match {
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case branch: Branch[?] with WithMetaData =>
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process(branch, parents)
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parents.push(branch)
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branch.contents.foreach { value => traverse(value, parents) } // Only .contents!
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parents.pop()
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writeMetadataCount(branch.metadata)
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case _ =>
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super.traverse(definition, parents)
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}
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}
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```
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**Result**:
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- Count for `doStatements` is written
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- Count for `undoStatements` is written
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- Items for `doStatements` are NEVER written (not in `.contents`)
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- Items for `undoStatements` are NEVER written (not in `.contents`)
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- Reader expects items after the count, reads garbage data
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- Deserialization fails with "Invalid string table index"
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### Affected Files
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**Writer**: `bast/shared/src/main/scala/com/ossuminc/riddl/bast/BASTWriter.scala`
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- Lines 655-660: `writeSagaStep()`
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- Lines 913-920: `writeIfThenElseStatement()`
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- Line 1682-1685: `writeContents()`
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**Reader**: `bast/shared/src/main/scala/com/ossuminc/riddl/bast/BASTReader.scala`
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- Lines 1660-1673: `readContentsDeferred()`
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### Impact
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- ✅ **Works**: Files without SagaStep or IfThenElseStatement (e.g., ToDoodles)
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- ❌ **Fails**: Files containing SagaStep or IfThenElseStatement (e.g., ShopifyCart)
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### Performance Impact
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When working correctly:
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- **Small files (12 nodes)**: 1.8x speedup over parsing
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- **Large files (510 nodes)**: 24.6x speedup over parsing (observed before deserialization failed)
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### Solution Options
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#### Option 1: Special-case traverse() for multi-Contents nodes
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Extend the `traverse()` override to detect and handle nodes with multiple Contents fields:
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```scala
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override protected def traverse(definition: RiddlValue, parents: ParentStack): Unit = {
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definition match {
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case ss: SagaStep =>
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process(ss, parents)
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parents.push(ss)
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ss.doStatements.foreach { value => traverse(value, parents) }
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ss.undoStatements.foreach { value => traverse(value, parents) }
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parents.pop()
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writeMetadataCount(ss.metadata)
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case ite: IfThenElseStatement =>
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process(ite, parents)
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parents.push(ite)
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ite.thens.foreach { value => traverse(value, parents) }
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ite.elses.foreach { value => traverse(value, parents) }
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parents.pop()
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// No metadata for statements
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case branch: Branch[?] with WithMetaData =>
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// ... existing code
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}
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}
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```
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**Pros**: Minimal changes, surgical fix
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**Cons**: Must remember to update for any future multi-Contents nodes
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#### Option 2: Refactor writeContents() to defer writing
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Change `writeContents()` to not write anything immediately. Instead, track pending Contents writes and emit them during traversal.
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**Pros**: More robust, handles any future cases
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**Cons**: Significant refactoring, more complex state management
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#### Option 3: Two-phase serialization
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Separate count-writing from item-writing phases.
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**Pros**: Clean separation of concerns
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**Cons**: Requires complete redesign of serialization
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### Recommended Fix
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**Option 1** (special-case traverse) is recommended because:
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1. Minimal code changes
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2. Easy to understand and verify
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3. Only 2 node types affected (possibly only 1 if IfThenElseStatement is removed)
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4. Fast to implement and test
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### Test Cases Needed
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After fix:
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1. ✅ Verify ToDoodles still works (regression test)
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2. ✅ Verify ShopifyCart serializes/deserializes correctly
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3. ✅ Create test specifically for SagaStep round-trip
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4. ✅ Create test for IfThenElseStatement round-trip (if not removed)
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5. ✅ Verify performance benchmarks still show speedup
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### Related Files
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- `bast/jvm/src/test/scala/com/ossuminc/riddl/bast/BenchmarkRunner.scala` - Performance benchmark
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- `bast/jvm/src/test/scala/com/ossuminc/riddl/bast/TestRunner.scala` - Round-trip test
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- `bast/shared/src/test/scala/com/ossuminc/riddl/bast/DeepASTComparison.scala` - Deep comparison utility
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### Notes
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- The issue does NOT affect metadata serialization (fixed in earlier session)
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- The issue does NOT affect Include node preservation (working correctly)
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- The issue does NOT affect location delta encoding (working correctly)
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- The issue ONLY affects nodes with multiple Contents fields
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---
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**Last Updated**: January 11, 2026
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**Severity**: High
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**Priority**: Must fix before production use

‎bast/jvm/src/test/scala/com/ossuminc/riddl/bast/BASTRoundTripTest.scala‎

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/*
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* Copyright 2019-2026 Ossum, Inc.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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package com.ossuminc.riddl.bast
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import com.ossuminc.riddl.language.AST.{Root, Nebula}
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import com.ossuminc.riddl.language.parsing.{RiddlParserInput, TopLevelParser}
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import com.ossuminc.riddl.passes.{Pass, PassInput}
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import com.ossuminc.riddl.utils.{pc, ec, Await, URL}
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import org.scalatest.TestData
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import org.scalatest.wordspec.AnyWordSpec
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import java.nio.file.{Files, Paths}
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import scala.concurrent.duration.*
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/** Round-trip tests for BAST serialization/deserialization
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*
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* These tests verify that: RIDDL text → AST → BAST binary → AST produces an equivalent AST
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*
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* This is the CRITICAL test for Phase 2 completion.
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*/
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class BASTRoundTripTest extends AnyWordSpec {
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"BAST Round Trip" should {
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"serialize and deserialize comprehensive test file" in { (td: TestData) =>
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val url = URL.fromCwdPath("bast/jvm/src/test/resources/comprehensive-test.riddl")
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val inputFuture = RiddlParserInput.fromURL(url, td.name)
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val result = Await.result(inputFuture.map { input =>
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// Step 1: Parse RIDDL text → AST
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val parseResult = TopLevelParser.parseInput(input, true)
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parseResult match {
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case Right(originalRoot: Root) =>
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println(s"\n=== Round Trip Test: comprehensive-test.riddl ===")
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println(s"Original AST parsed successfully")
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// Step 2: Serialize AST → BAST binary
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val passInput = PassInput(originalRoot)
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val writerResult = Pass.runThesePasses(passInput, Seq(BASTWriter.creator()))
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val output = writerResult.outputOf[BASTOutput](BASTWriter.name).get
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println(f"BAST written: ${output.bytes.length}%,d bytes (${output.nodeCount}%,d nodes)")
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// Step 3: Deserialize BAST binary → AST
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BASTReader.read(output.bytes) match {
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case Right(reconstructedNebula) =>
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println(s"BAST read: Nebula reconstructed")
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// Step 4: Compare original and reconstructed
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val areEqual = compareRoots(originalRoot, reconstructedNebula)
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if areEqual then
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println("✓ Round trip successful: Original AST == Reconstructed AST")
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else
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println("✗ Round trip FAILED: ASTs differ")
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end if
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areEqual
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case Left(errors) =>
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println(s"✗ Deserialization failed: ${errors.format}")
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false
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}
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case Left(messages) =>
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println(s"Parse failed: ${messages.format}")
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false
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}
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}, 30.seconds)
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assert(result, "Round trip test failed: ASTs are not equivalent")
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}
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"serialize and deserialize ToDoodles project" in { (td: TestData) =>
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val examplesPath = Paths.get("/Users/reid/Code/ossuminc/riddl-examples")
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if !Files.exists(examplesPath) then
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println("riddl-examples not found, skipping test")
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succeed
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else
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val url = URL.fromCwdPath("../riddl-examples/src/riddl/ToDoodles/ToDoodles.riddl")
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val inputFuture = RiddlParserInput.fromURL(url, td.name)
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val result = Await.result(inputFuture.map { input =>
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val parseResult = TopLevelParser.parseInput(input, true)
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parseResult match {
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case Right(originalRoot: Root) =>
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println(s"\n=== Round Trip Test: ToDoodles ===")
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// Serialize
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val passInput = PassInput(originalRoot)
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val writerResult = Pass.runThesePasses(passInput, Seq(BASTWriter.creator()))
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val output = writerResult.outputOf[BASTOutput](BASTWriter.name).get
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println(f"BAST written: ${output.bytes.length}%,d bytes")
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// Deserialize
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BASTReader.read(output.bytes) match {
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case Right(reconstructedNebula) =>
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// Compare
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val areEqual = compareRoots(originalRoot, reconstructedNebula)
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if areEqual then
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println("✓ Round trip successful")
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else
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println("✗ Round trip FAILED")
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end if
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areEqual
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case Left(errors) =>
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println(s"✗ Deserialization failed: ${errors.format}")
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false
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}
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case Left(messages) =>
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println(s"Parse failed: ${messages.format}")
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false
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}
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}, 30.seconds)
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assert(result, "Round trip test failed for ToDoodles")
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}
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"serialize and deserialize ReactiveBBQ domain" in { (td: TestData) =>
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val examplesPath = Paths.get("/Users/reid/Code/ossuminc/riddl-examples")
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if !Files.exists(examplesPath) then
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println("riddl-examples not found, skipping test")
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succeed
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else
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val url = URL.fromCwdPath("../riddl-examples/src/riddl/ReactiveBBQ/restaurant/domain.riddl")
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val inputFuture = RiddlParserInput.fromURL(url, td.name)
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val result = Await.result(inputFuture.map { input =>
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val parseResult = TopLevelParser.parseInput(input, true)
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parseResult match {
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case Right(originalRoot: Root) =>
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println(s"\n=== Round Trip Test: ReactiveBBQ Restaurant ===")
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// Serialize
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val passInput = PassInput(originalRoot)
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val writerResult = Pass.runThesePasses(passInput, Seq(BASTWriter.creator()))
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val output = writerResult.outputOf[BASTOutput](BASTWriter.name).get
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println(f"BAST written: ${output.bytes.length}%,d bytes")
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// Deserialize
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BASTReader.read(output.bytes) match {
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case Right(reconstructedNebula) =>
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// Compare
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val areEqual = compareRoots(originalRoot, reconstructedNebula)
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if areEqual then
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println("✓ Round trip successful")
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else
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println("✗ Round trip FAILED")
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end if
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areEqual
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case Left(errors) =>
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println(s"✗ Deserialization failed: ${errors.format}")
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false
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}
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case Left(messages) =>
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println(s"Parse failed: ${messages.format}")
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false
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}
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}, 30.seconds)
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assert(result, "Round trip test failed for ReactiveBBQ")
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}
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}
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/** Compare Root (original) with Nebula (reconstructed) for deep structural equality
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*
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* Note: BASTWriter writes Root using NODE_NEBULA tag, so deserialization produces Nebula.
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* This is expected - we're comparing the CONTENT, not the container type.
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*
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* Uses DeepASTComparison to recursively verify all fields, identifiers, locations, and nested content.
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*/
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private def compareRoots(original: Root, reconstructed: Nebula): Boolean = {
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println(s"\n=== Deep Structural Comparison ===")
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println(s"Original: Root with ${original.contents.toSeq.size} top-level elements")
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println(s"Reconstructed: Nebula with ${reconstructed.contents.toSeq.size} top-level elements")
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// Perform deep comparison
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val results = DeepASTComparison.compareRootAndNebula(original, reconstructed)
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// Generate report
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val report = DeepASTComparison.report(results)
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println(report)
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// Check if all comparisons succeeded
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val allSucceeded = results.forall(_.isSuccess)
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if allSucceeded then
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println("✓ Complete structural reflectivity verified: AST → BAST → AST preserves all data")
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else
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println("✗ Structural differences detected - see failures above")
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end if
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allSucceeded
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}
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}

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