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Add rudimentary form of error recovery to parser
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When we encounter a parser error, we'll now attempt some basic
error recovery by simply skipping token until we reach a token at
the start of a line that is an identifier, documentation comment,
or '@'. This should help with things like LSPs that still should be
able to utilize jump to definition even with a broken or in-progress
model.

Add error recovery to control statements and metadata. Ensure that
invalid identifiers are turned into ERROR tokens instead of throwing.
Error recovery will also consider "$" a recovery token.
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@mtdowling
mtdowling committed Apr 19, 2023
1 parent 94bf11b commit d1ebe68
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Showing 8 changed files with 317 additions and 80 deletions.
203 changes: 126 additions & 77 deletions smithy-model/src/main/java/software/amazon/smithy/model/loader/IdlModelLoader.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -232,44 +232,48 @@ private void parseControlSection() {
Set<CharSequence> definedKeys = new HashSet<>();

while (tokenizer.getCurrentToken() == IdlToken.DOLLAR) {
tokenizer.next();
tokenizer.expect(IdlToken.IDENTIFIER, IdlToken.STRING);
String key = tokenizer.internString(tokenizer.getCurrentTokenStringSlice());
try {
tokenizer.next();
tokenizer.expect(IdlToken.IDENTIFIER, IdlToken.STRING);
String key = tokenizer.internString(tokenizer.getCurrentTokenStringSlice());

tokenizer.next();
tokenizer.skipSpaces();
tokenizer.expect(IdlToken.COLON);
tokenizer.next();
tokenizer.skipSpaces();
tokenizer.next();
tokenizer.skipSpaces();
tokenizer.expect(IdlToken.COLON);
tokenizer.next();
tokenizer.skipSpaces();

if (!definedKeys.add(key)) {
throw syntax(format("Duplicate control statement `%s`", key));
}
if (!definedKeys.add(key)) {
throw syntax(format("Duplicate control statement `%s`", key));
}

Node value = IdlNodeParser.expectAndSkipNode(tokenizer, resolver);
Node value = IdlNodeParser.expectAndSkipNode(tokenizer, resolver);

switch (key) {
case "version":
onVersion(value);
break;
case "operationInputSuffix":
operationInputSuffix = value.expectStringNode().getValue();
break;
case "operationOutputSuffix":
operationOutputSuffix = value.expectStringNode().getValue();
break;
default:
emit(ValidationEvent.builder()
.id(Validator.MODEL_ERROR)
.sourceLocation(value)
.severity(Severity.WARNING)
.message(format("Unknown control statement `%s` with value `%s",
key, Node.printJson(value)))
.build());
break;
}
switch (key) {
case "version":
onVersion(value);
break;
case "operationInputSuffix":
operationInputSuffix = value.expectStringNode().getValue();
break;
case "operationOutputSuffix":
operationOutputSuffix = value.expectStringNode().getValue();
break;
default:
emit(ValidationEvent.builder()
.id(Validator.MODEL_ERROR)
.sourceLocation(value)
.severity(Severity.WARNING)
.message(format("Unknown control statement `%s` with value `%s",
key, Node.printJson(value)))
.build());
break;
}

tokenizer.expectAndSkipBr();
tokenizer.expectAndSkipBr();
} catch (ModelSyntaxException e) {
errorRecovery(e);
}
}
}

Expand All @@ -293,19 +297,23 @@ private void onVersion(Node value) {

private void parseMetadataSection() {
while (tokenizer.doesCurrentIdentifierStartWith('m')) {
tokenizer.expectCurrentLexeme("metadata");
tokenizer.next(); // skip "metadata"
tokenizer.expectAndSkipSpaces();
tokenizer.expect(IdlToken.IDENTIFIER, IdlToken.STRING);
String key = tokenizer.internString(tokenizer.getCurrentTokenStringSlice());
tokenizer.next();
tokenizer.skipSpaces();
tokenizer.expect(IdlToken.EQUAL);
tokenizer.next();
tokenizer.skipSpaces();
Node value = IdlNodeParser.expectAndSkipNode(tokenizer, resolver);
operations.accept(new LoadOperation.PutMetadata(modelVersion, key, value));
tokenizer.expectAndSkipBr();
try {
tokenizer.expectCurrentLexeme("metadata");
tokenizer.next(); // skip "metadata"
tokenizer.expectAndSkipSpaces();
tokenizer.expect(IdlToken.IDENTIFIER, IdlToken.STRING);
String key = tokenizer.internString(tokenizer.getCurrentTokenStringSlice());
tokenizer.next();
tokenizer.skipSpaces();
tokenizer.expect(IdlToken.EQUAL);
tokenizer.next();
tokenizer.skipSpaces();
Node value = IdlNodeParser.expectAndSkipNode(tokenizer, resolver);
operations.accept(new LoadOperation.PutMetadata(modelVersion, key, value));
tokenizer.expectAndSkipBr();
} catch (ModelSyntaxException e) {
errorRecovery(e);
}
}
}

Expand Down Expand Up @@ -415,51 +423,92 @@ private void parseApplyStatement() {

private void parseFirstShapeStatement(SourceLocation possibleDocCommentLocation) {
if (tokenizer.getCurrentToken() != IdlToken.EOF) {
if (tokenizer.doesCurrentIdentifierStartWith('a')) {
parseApplyStatement();
} else {
List<IdlTraitParser.Result> traits;
boolean hasDocComment = tokenizer.getCurrentToken() == IdlToken.DOC_COMMENT;

if (possibleDocCommentLocation == null) {
traits = IdlTraitParser.parseDocsAndTraitsBeforeShape(tokenizer, resolver);
try {
if (tokenizer.doesCurrentIdentifierStartWith('a')) {
parseApplyStatement();
} else {
// In this case, this is the first shape encountered for a model file that doesn't have any
// use statements. We need to take the previously skipped documentation comments to parse
// potential use statements and apply them to this first shape.
String docLines = tokenizer.removePendingDocCommentLines();
traits = IdlTraitParser.parseDocsAndTraitsBeforeShape(tokenizer, resolver);
// Note that possibleDocCommentLocation is just a mark of where docs _could be_.
if (docLines != null) {
hasDocComment = true;
traits.add(new IdlTraitParser.Result(DocumentationTrait.ID.toString(),
new StringNode(docLines, possibleDocCommentLocation),
IdlTraitParser.TraitType.DOC_COMMENT));
List<IdlTraitParser.Result> traits;
boolean hasDocComment = tokenizer.getCurrentToken() == IdlToken.DOC_COMMENT;

if (possibleDocCommentLocation == null) {
traits = IdlTraitParser.parseDocsAndTraitsBeforeShape(tokenizer, resolver);
} else {
// In this case, this is the first shape encountered for a model file that doesn't have any
// use statements. We need to take the previously skipped documentation comments to parse
// potential use statements and apply them to this first shape.
String docLines = tokenizer.removePendingDocCommentLines();
traits = IdlTraitParser.parseDocsAndTraitsBeforeShape(tokenizer, resolver);
// Note that possibleDocCommentLocation is just a mark of where docs _could be_.
if (docLines != null) {
hasDocComment = true;
traits.add(new IdlTraitParser.Result(DocumentationTrait.ID.toString(),
new StringNode(docLines, possibleDocCommentLocation),
IdlTraitParser.TraitType.DOC_COMMENT));
}
}
}

if (parseShapeDefinition(traits, hasDocComment)) {
parseShape(traits);
if (parseShapeDefinition(traits, hasDocComment)) {
parseShape(traits);
}
}
} catch (ModelSyntaxException e) {
errorRecovery(e);
}
}
}

private void parseSubsequentShapeStatements() {
while (tokenizer.getCurrentToken() != IdlToken.EOF) {
if (tokenizer.doesCurrentIdentifierStartWith('a')) {
parseApplyStatement();
} else {
List<IdlTraitParser.Result> traits;
boolean hasDocComment = tokenizer.getCurrentToken() == IdlToken.DOC_COMMENT;
traits = IdlTraitParser.parseDocsAndTraitsBeforeShape(tokenizer, resolver);
if (parseShapeDefinition(traits, hasDocComment)) {
parseShape(traits);
while (tokenizer.hasNext()) {
try {
if (tokenizer.doesCurrentIdentifierStartWith('a')) {
parseApplyStatement();
} else {
List<IdlTraitParser.Result> traits;
boolean hasDocComment = tokenizer.getCurrentToken() == IdlToken.DOC_COMMENT;
traits = IdlTraitParser.parseDocsAndTraitsBeforeShape(tokenizer, resolver);
if (parseShapeDefinition(traits, hasDocComment)) {
parseShape(traits);
}
}
} catch (ModelSyntaxException e) {
errorRecovery(e);
}
}
}

private void errorRecovery(ModelSyntaxException e) {
if (!tokenizer.hasNext()) {
throw e;
}

// Here we do rudimentary error recovery to attempt to make sense of the remaining model.
// We do this by scanning tokens until we find the next "$", identifier, docs, or trait at the start of a line.
// The model is still invalid and will fail to validate, but things like IDEs should still be able to do
// things like goto definition.
emit(ValidationEvent.fromSourceException(e));

do {
// Always skip the current token since it was the one that failed.
IdlToken token = tokenizer.next();
if (tokenizer.getCurrentTokenColumn() == 1 && isErrorRecoveryToken(token)) {
break;
}
} while (tokenizer.hasNext());
}

// These tokens are good signals that the next shape is starting.
private boolean isErrorRecoveryToken(IdlToken token) {
switch (token) {
case IDENTIFIER:
case DOC_COMMENT:
case AT:
case DOLLAR:
return true;
default:
return false;
}
}

private boolean parseShapeDefinition(List<IdlTraitParser.Result> traits, boolean hasDocComment) {
if (tokenizer.getCurrentToken() != IdlToken.EOF) {
// Continue to parse if not at the end of the file.
Expand Down
12 changes: 9 additions & 3 deletions smithy-model/src/main/java/software/amazon/smithy/model/loader/IdlTokenizer.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -321,7 +321,7 @@ public IdlToken next() {
switch (c) {
case SimpleParser.EOF:
if (currentTokenType == IdlToken.EOF) {
throw new NoSuchElementException("Expected another token but traversed beyond EOF");
throw new NoSuchElementException("Expected another token but reached EOF");
}
currentTokenEnd = parser.position();
return currentTokenType = IdlToken.EOF;
Expand Down Expand Up @@ -750,9 +750,15 @@ private IdlToken parseNumber() {
}

private IdlToken parseIdentifier() {
ParserUtils.consumeIdentifier(parser);
try {
ParserUtils.consumeIdentifier(parser);
currentTokenType = IdlToken.IDENTIFIER;
} catch (RuntimeException e) {
currentTokenType = IdlToken.ERROR;
currentTokenError = e.getMessage();
}
currentTokenEnd = parser.position();
return currentTokenType = IdlToken.IDENTIFIER;
return currentTokenType;
}

private IdlToken parseString() {
Expand Down
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