fix: Abort completion computations when encountering a BadLocationException

org.eclipse.lsp4e.test/src/org/eclipse/lsp4e/test/edit/LSPEclipseUtilsTest.java

@@ -510,9 +510,9 @@
 		var file = TestUtils.createFile(project, "dummy" + new Random().nextInt(), "");
 		var triggerChars = new  char[] {':', '>'};
 		// When toCompletionParams get called with offset == 0 and document.getLength() == 0:
 		var param = LSPEclipseUtils.toCompletionParams(file.getLocationURI(), 0, LSPEclipseUtils.getDocument(file), triggerChars);
 		// Then no context has been added to param:
-		assertNull(param.getContext());
+		assertEquals(param.getContext().getTriggerKind(), CompletionTriggerKind.Invoked);
 	}
 
 	@Test
@@ -521,7 +521,7 @@
 		var file = TestUtils.createFile(project, "dummy" + new Random().nextInt(), "std");
 		var triggerChars = new  char[] {':', '>'};
 		// When toCompletionParams get called with offset == 0 and document.getLength() > 0:
 		var param = LSPEclipseUtils.toCompletionParams(file.getLocationURI(), 0, LSPEclipseUtils.getDocument(file), triggerChars);
 		// Then the trigger kind is Invoked:
 		assertEquals(param.getContext().getTriggerKind(), CompletionTriggerKind.Invoked);
 	}
@@ -532,7 +532,7 @@
 		var file = TestUtils.createFile(project, "dummy" + new Random().nextInt(), "std:");
 		var triggerChars = new  char[] {':', '>'};
 		// When toCompletionParams get called with offset > 0 and document.getLength() > 0:
 		var param = LSPEclipseUtils.toCompletionParams(file.getLocationURI(), 4, LSPEclipseUtils.getDocument(file), triggerChars);
 		// Then the context has been added with a colon as trigger character:
 		assertEquals(param.getContext().getTriggerCharacter(), ":");
 		// And the trigger kind is TriggerCharacter:
@@ -545,7 +545,7 @@
 		var file = TestUtils.createFile(project, "dummy" + new Random().nextInt(), "std");
 		var triggerChars = new  char[] {':', '>'};
 		// When toCompletionParams get called with offset > 0 and document.getLength() > 0:
 		var param = LSPEclipseUtils.toCompletionParams(file.getLocationURI(), 3, LSPEclipseUtils.getDocument(file), triggerChars);
 		// Then the trigger kind is Invoked:
 		assertEquals(param.getContext().getTriggerKind(), CompletionTriggerKind.Invoked);
 	}

org.eclipse.lsp4e/src/org/eclipse/lsp4e/LSPEclipseUtils.java

@@ -240,30 +240,47 @@ public static boolean isOffsetInRange(int offset, Range range, IDocument documen
 		}
 	}
 
-	public static CompletionParams toCompletionParams(URI fileUri, int offset, IDocument document, char[] completionTriggerChars)
-			throws BadLocationException {
-		Position start = toPosition(offset, document);
-		final var param = new CompletionParams();
+	/**
+	 * Provides the character at the given offset or {@code null} if the document is empty.
+	 */
+	public static @Nullable Character getCharacterAtPosition(IDocument document, int offset) throws BadLocationException {
 		if (document.getLength() > 0) {
-			try {
-				int positionCharacterOffset = offset > 0 ? offset-1 : offset;
-				String positionCharacter = document.get(positionCharacterOffset, 1);
-				if (Chars.contains(completionTriggerChars, positionCharacter.charAt(0))) {
-					param.setContext(new CompletionContext(CompletionTriggerKind.TriggerCharacter, positionCharacter));
-				} else {
-					// According to LSP 3.17 specification: the triggerCharacter in CompletionContext is undefined if
-					// triggerKind != CompletionTriggerKind.TriggerCharacter
-					param.setContext(new CompletionContext(CompletionTriggerKind.Invoked));
-				}
-			} catch (BadLocationException e) {
-				LanguageServerPlugin.logError(e);
-			}
+			int positionCharacterOffset = offset > 0 ? offset - 1 : offset;
+			return document.getChar(positionCharacterOffset);
+		}
+		return null;
+	}
+
+	public static CompletionContext toCompletionContext(@Nullable Character triggerChar, char[] completionTriggerChars) {
+		if (triggerChar == null || !Chars.contains(completionTriggerChars, triggerChar.charValue())) {
+			// According to LSP 3.17 specification: the triggerCharacter in
+			// CompletionContext is undefined if
+			// triggerKind != CompletionTriggerKind.TriggerCharacter
+			return new CompletionContext(CompletionTriggerKind.Invoked);
+		} else {
+			return new CompletionContext(CompletionTriggerKind.TriggerCharacter, triggerChar.toString());
 		}
+	}
+
+	public static CompletionParams toCompletionParams(URI fileUri, Position start, CompletionContext context) {
+		final var param = new CompletionParams();
+		param.setContext(context);
 		param.setPosition(start);
 		param.setTextDocument(toTextDocumentIdentifier(fileUri));
 		return param;
 	}
 
+	/**
+	 * Use {@link #toCompletionParams(URI, Position, CompletionContext)} instead.
+	 */
+	@Deprecated(forRemoval = true)
+	public static CompletionParams toCompletionParams(URI fileUri, int offset, IDocument document, char[] completionTriggerChars)
+			throws BadLocationException {
+		Position start = toPosition(offset, document);
+		@Nullable Character triggerChar = getCharacterAtPosition(document, offset);
+		return toCompletionParams(fileUri, start, toCompletionContext(triggerChar, completionTriggerChars));
+	}
+
 	public static @Nullable ITextSelection toSelection(Range range, IDocument document) {
 		try {
 			int offset = toOffset(range.getStart(), document);

org.eclipse.lsp4e/src/org/eclipse/lsp4e/operations/completion/LSCompletionProposal.java

@@ -234,7 +234,9 @@ public int getRankScore() {
 			rankScore = CompletionProposalTools.getScoreOfFilterMatch(getDocumentFilter(),
 					getFilterString());
 		} catch (BadLocationException e) {
-			LanguageServerPlugin.logError(e);
+			// Document was changed while we computed completion proposals, which made the
+			// offset invalid. We can stop any further computation as the result will be
+			// discarded anyway.
 			rankScore = -1;
 		}
 		this.rankScore = rankScore;
@@ -257,7 +259,9 @@ public int getRankCategory() {
 			rankCategory = CompletionProposalTools.getCategoryOfFilterMatch(getDocumentFilter(),
 					getFilterString());
 		} catch (BadLocationException e) {
-			LanguageServerPlugin.logError(e);
+			// Document was changed while we computed completion proposals, which made the
+			// offset invalid. We can stop any further computation as the result will be
+			// discarded anyway.
 			rankCategory = CompletionProposalTools.CATEGORY_NO_MATCH;
 		}
 		this.rankCategory = rankCategory;
@@ -442,27 +446,25 @@ private void updateCompletionItem(@Nullable CompletionItem resolvedItem) {
 
 	@Override
 	public int getPrefixCompletionStart(IDocument document, int completionOffset) {
-		Either<TextEdit, InsertReplaceEdit> textEdit = item.getTextEdit();
-		if (textEdit != null) {
-			try {
+		try {
+			Either<TextEdit, InsertReplaceEdit> textEdit = item.getTextEdit();
+			if (textEdit != null) {
 				return LSPEclipseUtils.toOffset(getTextEditRange().getStart(), document);
-			} catch (BadLocationException e) {
-				LanguageServerPlugin.logError(e);
 			}
-		}
-		final String insertText = getInsertText();
-		final int insertTextLength = insertText.length();
-		try {
-			String subDoc = document.get(
-					Math.max(0, completionOffset - insertTextLength),
+
+			final String insertText = getInsertText();
+			final int insertTextLength = insertText.length();
+			String subDoc = document.get(Math.max(0, completionOffset - insertTextLength),
 					Math.min(insertTextLength, completionOffset));
 			for (int i = 0; i < insertTextLength && i < completionOffset; i++) {
 				if (insertText.regionMatches(true, 0, subDoc, i, subDoc.length() - i)) {
 					return completionOffset - subDoc.substring(i).length();
 				}
 			}
 		} catch (BadLocationException e) {
-			LanguageServerPlugin.logError(e);
+			// Document was changed while we computed completion proposals, which made the
+			// offset invalid. We can stop any further computation as the result will be
+			// discarded anyway.
 		}
 		return completionOffset;
 	}

org.eclipse.lsp4e/src/org/eclipse/lsp4e/operations/completion/LSContentAssistProcessor.java

@@ -51,10 +51,12 @@
 import org.eclipse.lsp4e.internal.CancellationUtil;
 import org.eclipse.lsp4e.ui.Messages;
 import org.eclipse.lsp4e.ui.UI;
+import org.eclipse.lsp4j.CompletionContext;
 import org.eclipse.lsp4j.CompletionItem;
 import org.eclipse.lsp4j.CompletionItemDefaults;
 import org.eclipse.lsp4j.CompletionList;
 import org.eclipse.lsp4j.CompletionParams;
+import org.eclipse.lsp4j.Position;
 import org.eclipse.lsp4j.SignatureHelpParams;
 import org.eclipse.lsp4j.SignatureInformation;
 import org.eclipse.lsp4j.jsonrpc.CancelChecker;
@@ -116,21 +118,28 @@ public ICompletionProposal[] computeCompletionProposals(ITextViewer viewer, int
 			return NO_COMPLETION_PROPOSALS;
 		}
 
+		final @Nullable Character triggerChar;
+		final Position completionPosition;
+		try {
+			// Eagerly to try to access the position, so we can fail fast.
+			triggerChar = LSPEclipseUtils.getCharacterAtPosition(document, offset);
+			completionPosition = LSPEclipseUtils.toPosition(offset, document);
+		} catch (BadLocationException e) {
+			// Document was changed while we computed completion proposals, which made the
+			// offset invalid. We can stop any further computation as the result will be
+			// discarded anyway.
+			return NO_COMPLETION_PROPOSALS;
+		}
+
 		URI uri = LSPEclipseUtils.toUri(document);
 		if (uri == null) {
 			return NO_COMPLETION_PROPOSALS;
 		}
 
 		initiateLanguageServers(document);
-		CompletionParams param;
 
-		try {
-			param = LSPEclipseUtils.toCompletionParams(uri, offset, document, this.completionTriggerChars);
-		} catch (BadLocationException e) {
-			LanguageServerPlugin.logError(e);
-			this.errorMessage = createErrorMessage(offset, e);
-			return createErrorProposal(offset, e);
-		}
+		final CompletionContext context = LSPEclipseUtils.toCompletionContext(triggerChar, completionTriggerChars);
+		final CompletionParams param = LSPEclipseUtils.toCompletionParams(uri, completionPosition, context);
 
 		final var proposals = Collections.synchronizedList(new ArrayList<ICompletionProposal>());
 		final var anyIncomplete = new AtomicBoolean(false);