Correctly handle corrupt SMT models

src/SIL.Machine.Tool/CorpusCommandSpecBase.cs

@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using System.IO;
-using System.Linq;
 using McMaster.Extensions.CommandLineUtils;
 using SIL.Machine.Corpora;
 

src/SIL.Machine.Tool/ParallelCorpusCommandSpec.cs

@@ -1,5 +1,4 @@
-using System.Collections.Generic;
-using System.IO;
+using System.IO;
 using McMaster.Extensions.CommandLineUtils;
 using SIL.Machine.Corpora;
 using SIL.Machine.Tokenization;

src/SIL.Machine.Translation.Thot/SIL.Machine.Translation.Thot.csproj

@@ -8,7 +8,7 @@
   <Import Project="../AssemblyInfo.props" />
 
   <ItemGroup>
-    <PackageReference Include="Thot" Version="3.4.1" />
+    <PackageReference Include="Thot" Version="3.4.2" />
   </ItemGroup>
 
   <ItemGroup>

src/SIL.Machine.Translation.Thot/Thot.cs

@@ -613,8 +613,10 @@ IReadOnlyList<string> targetSegment
         public static IntPtr LoadSmtModel(ThotWordAlignmentModelType alignmentModelType, ThotSmtParameters parameters)
         {
             IntPtr handle = smtModel_create(GetAlignmentModelType(alignmentModelType, incremental: true));
-            smtModel_loadTranslationModel(handle, parameters.TranslationModelFileNamePrefix);
-            smtModel_loadLanguageModel(handle, parameters.LanguageModelFileNamePrefix);
+            if (!smtModel_loadTranslationModel(handle, parameters.TranslationModelFileNamePrefix))
+                throw new InvalidOperationException("Unable to load translation model.");
+            if (!smtModel_loadLanguageModel(handle, parameters.LanguageModelFileNamePrefix))
+                throw new InvalidOperationException("Unable to load language model.");
             smtModel_setNonMonotonicity(handle, parameters.ModelNonMonotonicity);
             smtModel_setW(handle, parameters.ModelW);
             smtModel_setA(handle, parameters.ModelA);
@@ -650,7 +652,10 @@ public static IntPtr CreateAlignmentModel(ThotWordAlignmentModelType type, IntPt
 
         public static IntPtr OpenAlignmentModel(ThotWordAlignmentModelType type, string prefFileName)
         {
-            return swAlignModel_open(GetAlignmentModelType(type, incremental: false), prefFileName);
+            IntPtr handle = swAlignModel_open(GetAlignmentModelType(type, incremental: false), prefFileName);
+            if (handle == IntPtr.Zero)
+                throw new InvalidOperationException("Unable to load word alignment model.");
+            return handle;
         }
 
         public static AlignmentModelType GetAlignmentModelType(ThotWordAlignmentModelType type, bool incremental)

src/SIL.Machine.Translation.Thot/ThotSmtModel.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -31,6 +32,12 @@ public ThotSmtModel(ThotWordAlignmentModelType wordAlignmentModelType, string cf
 
         public ThotSmtModel(ThotWordAlignmentModelType wordAlignmentModelType, ThotSmtParameters parameters)
         {
+            if (!File.Exists(parameters.TranslationModelFileNamePrefix + ".ttable"))
+                throw new FileNotFoundException("The translation model could not be found.");
+
+            if (!File.Exists(parameters.LanguageModelFileNamePrefix))
+                throw new FileNotFoundException("The language model could not be found.");
+
             _decoderPool = new ObjectPool<ThotSmtDecoder>(MaxDecoderPoolSize, () => new ThotSmtDecoder(this));
 
             Parameters = parameters;
@@ -605,7 +612,8 @@ protected override void DisposeManagedResources()
 
         protected override void DisposeUnmanagedResources()
         {
-            Thot.smtModel_close(_handle);
+            if (_handle != IntPtr.Zero)
+                Thot.smtModel_close(_handle);
         }
 
         private double GetWordAlignmentScore(

tests/SIL.Machine.Translation.Thot.Tests/ThotFastAlignWordAlignmentModelTests.cs

@@ -1,4 +1,5 @@
 using NUnit.Framework;
+using SIL.Machine.Utils;
 
 namespace SIL.Machine.Translation.Thot
 {
@@ -165,5 +166,14 @@ public void GetAvgTranslationScore_Symmetrized()
             double score = model.GetAvgTranslationScore(sourceSegment, targetSegment, alignment);
             Assert.That(score, Is.EqualTo(0.36).Within(0.01));
         }
+
+        [Test]
+        public void Constructor_ModelCorrupted()
+        {
+            using var tempDir = new TempDirectory("ThotFastAlignWordAlignmentModelTests");
+            string modelPrefix = Path.Combine(tempDir.Path, "src_trg_invswm");
+            File.WriteAllText(modelPrefix + ".src", "corrupted");
+            Assert.Throws<InvalidOperationException>(() => new ThotFastAlignWordAlignmentModel(modelPrefix));
+        }
     }
 }

tests/SIL.Machine.Translation.Thot.Tests/ThotSmtModelTests.cs

@@ -1,4 +1,5 @@
 using NUnit.Framework;
+using SIL.Machine.Utils;
 
 namespace SIL.Machine.Translation.Thot
 {
@@ -189,6 +190,45 @@ public async Task GetWordGraphAsync_EmptySegment_FastAlign()
             Assert.That(wordGraph.IsEmpty, Is.True);
         }
 
+        [Test]
+        public void Constructor_ModelDoesNotExist()
+        {
+            Assert.Throws<FileNotFoundException>(
+                () =>
+                    new ThotSmtModel(
+                        ThotWordAlignmentModelType.Hmm,
+                        new ThotSmtParameters
+                        {
+                            TranslationModelFileNamePrefix = "does-not-exist",
+                            LanguageModelFileNamePrefix = "does-not-exist"
+                        }
+                    )
+            );
+        }
+
+        [Test]
+        public void Constructor_ModelCorrupted()
+        {
+            using var tempDir = new TempDirectory("ThotSmtModelTests");
+            string tmDir = Path.Combine(tempDir.Path, "tm");
+            Directory.CreateDirectory(tmDir);
+            File.WriteAllText(Path.Combine(tmDir, "src_trg.ttable"), "corrupted");
+            string lmDir = Path.Combine(tempDir.Path, "lm");
+            Directory.CreateDirectory(lmDir);
+            File.WriteAllText(Path.Combine(lmDir, "trg.lm"), "corrupted");
+            Assert.Throws<InvalidOperationException>(
+                () =>
+                    new ThotSmtModel(
+                        ThotWordAlignmentModelType.Hmm,
+                        new ThotSmtParameters
+                        {
+                            TranslationModelFileNamePrefix = Path.Combine(tmDir, "src_trg"),
+                            LanguageModelFileNamePrefix = Path.Combine(lmDir, "trg.lm")
+                        }
+                    )
+            );
+        }
+
         private static ThotSmtModel CreateHmmModel()
         {
             return new ThotSmtModel(ThotWordAlignmentModelType.Hmm, TestHelpers.ToyCorpusHmmConfigFileName);