fix(developer): handle missing files in kmc-model

If a file is not found, loadfile returns null, which kmc-model now
handles with a clear error message rather than a generic exception.
Checks added for missing .model.ts and missing wordlist.tsv files. Added
corresponding unit tests.

Fixes: #12553
Fixes: KEYMAN-DEVELOPER-294

developer/src/kmc-model/src/build-trie.ts

@@ -169,6 +169,9 @@ class WordListFromFilename {
 
   *lines() {
     const data = callbacks.loadFile(this.name);
+    if(!data) {
+      throw new ModelCompilerError(ModelCompilerMessages.Error_WordlistFileNotFound({filename:this.name}));
+    }
     const contents = new TextDecoder(detectEncoding(data)).decode(data);
     yield *enumerateLines(contents.split(NEWLINE_SEPARATOR));
   }

developer/src/kmc-model/src/lexical-model-compiler.ts

@@ -125,7 +125,11 @@ export class LexicalModelCompiler implements KeymanCompiler {
    */
   public loadFromFilename(filename: string): LexicalModelSource {
 
-    let sourceCode = new TextDecoder().decode(callbacks.loadFile(filename));
+    const data = callbacks.loadFile(filename);
+    if(!data) {
+      throw new ModelCompilerError(ModelCompilerMessages.Error_ModelFileNotFound({filename}));
+    }
+    let sourceCode = new TextDecoder().decode(data);
     // Compile the module to JavaScript code.
     // NOTE: transpile module does a very simple TS to JS compilation.
     // It DOES NOT check for types!

developer/src/kmc-model/src/model-compiler-messages.ts

@@ -7,8 +7,8 @@ const SevHint = CompilerErrorSeverity.Hint | Namespace;
 const SevError = CompilerErrorSeverity.Error | Namespace;
 const SevFatal = CompilerErrorSeverity.Fatal | Namespace;
 
-const m = (code: number, message: string) : CompilerEvent => ({
-  ...CompilerMessageSpec(code, message),
+const m = (code: number, message: string, detail?: string) : CompilerEvent => ({
+  ...CompilerMessageSpec(code, message, detail),
   line: ModelCompilerMessageContext.line,
   filename: ModelCompilerMessageContext.filename,
 });
@@ -70,6 +70,24 @@ export class ModelCompilerMessages {
   static ERROR_UnsupportedScriptOverride = SevError | 0x000A;
   static Error_UnsupportedScriptOverride = (o:{option:string}) => m(this.ERROR_UnsupportedScriptOverride,
     `Unsupported script override: ${def(o.option)}`);
+
+  static ERROR_ModelFileNotFound = SevError | 0x000B;
+  static Error_ModelFileNotFound = (o:{filename:string}) => m(
+    this.ERROR_ModelFileNotFound,
+    `Lexical model source file ${def(o.filename)} was not found`,
+    `The model source file was not found on the disk. Verify that you have
+    the correct path to the file.`
+  );
+
+  static ERROR_WordlistFileNotFound = SevError | 0x000C;
+  static Error_WordlistFileNotFound = (o:{filename:string}) => m(
+    this.ERROR_WordlistFileNotFound,
+    `Wordlist file ${def(o.filename)} was not found`,
+    `The wordlist file was not found on the disk. Verify that you have
+    the correct path to the file.`
+  );
+
+
 };
 
 /**

developer/src/kmc-model/test/fixtures/invalid-models/example.qaa.missing-wordlist/example.qaa.missing-wordlist.model.ts

@@ -0,0 +1,5 @@
+const source: LexicalModelSource = {
+  format: 'trie-1.0',
+  sources: ['wordlist.tsv'],
+};
+export default source;

developer/src/kmc-model/test/test-messages.ts

@@ -1,10 +1,62 @@
 import 'mocha';
+import { assert } from 'chai';
 import { ModelCompilerMessages } from '../src/model-compiler-messages.js';
-import { verifyCompilerMessagesObject } from '@keymanapp/developer-test-helpers';
+import { TestCompilerCallbacks, verifyCompilerMessagesObject } from '@keymanapp/developer-test-helpers';
 import { CompilerErrorNamespace } from '@keymanapp/developer-utils';
+import { LexicalModelCompiler } from '../src/lexical-model-compiler.js';
+import { makePathToFixture } from './helpers/index.js';
 
 describe('ModelCompilerMessages', function () {
+
+  const callbacks = new TestCompilerCallbacks();
+
+  this.beforeEach(function() {
+    callbacks.clear();
+  });
+
+  this.afterEach(function() {
+    if(this.currentTest?.isFailed()) {
+      callbacks.printMessages();
+    }
+  });
+
   it('should have a valid ModelCompilerMessages object', function() {
     return verifyCompilerMessagesObject(ModelCompilerMessages, CompilerErrorNamespace.ModelCompiler);
   });
+
+  async function testForMessage(fixture: string[], messageId?: number) {
+    const compiler = new LexicalModelCompiler();
+    assert.isTrue(await compiler.init(callbacks, null));
+
+    const modelPath = makePathToFixture(...fixture);
+
+    // Note: throwing away compile results (just to memory)
+    await compiler.run(modelPath, null);
+
+    if(messageId) {
+      assert.isTrue(callbacks.hasMessage(messageId), `messageId ${messageId.toString(16)} not generated, instead got: `+JSON.stringify(callbacks.messages,null,2));
+      assert.lengthOf(callbacks.messages, 1, `messages should have 1 entry, instead has: `+JSON.stringify(callbacks.messages,null,2));
+    } else {
+      assert.lengthOf(callbacks.messages, 0, `messages should be empty, but instead got: `+JSON.stringify(callbacks.messages,null,2));
+    }
+  }
+
+  // ERROR_ModelFileNotFound
+
+  it('should generate ERROR_ModelFileNotFound if a .model.ts file is missing', async function() {
+    await testForMessage(
+      ['invalid-models', 'missing-file.model.ts'],
+      ModelCompilerMessages.ERROR_ModelFileNotFound
+    );
+  });
+
+  // ERROR_WordlistFileNotFound
+
+  it('should generate ERROR_WordlistFileNotFound if a .tsv file is missing', async function() {
+    await testForMessage(
+      ['invalid-models', 'example.qaa.missing-wordlist', 'example.qaa.missing-wordlist.model.ts'],
+      ModelCompilerMessages.ERROR_WordlistFileNotFound
+    );
+  });
+
 });