net.sf.saxon.expr.ItemChecker Maven / Gradle / Ivy
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.expr;
import net.sf.saxon.event.Outputter;
import net.sf.saxon.event.TypeCheckingFilter;
import net.sf.saxon.expr.elab.*;
import net.sf.saxon.expr.instruct.Block;
import net.sf.saxon.expr.instruct.TailCall;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.pattern.CombinedNodeTest;
import net.sf.saxon.pattern.DocumentNodeTest;
import net.sf.saxon.pattern.NodeTest;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.SaxonErrorCode;
import net.sf.saxon.trans.UncheckedXPathException;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.*;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.IntegerValue;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Consumer;
import java.util.function.Supplier;
/**
* A ItemChecker implements the item type checking of "treat as": that is,
* it returns the supplied sequence, checking that all its items are of the correct type.
* It is used both for actual "treat as" expressions, and more commonly, for the
* run-time type checking invoked by function calls. Note that these differ in the
* error code produced when type checking fails.
*/
public final class ItemChecker extends UnaryExpression {
private final ItemType requiredItemType;
private final Supplier roleSupplier;
/**
* Constructor
*
* @param sequence the expression whose value we are checking
* @param itemType the required type of the items in the sequence
* @param roleSupplier information used in constructing an error message
*/
public ItemChecker(Expression sequence, ItemType itemType, Supplier roleSupplier) {
super(sequence);
requiredItemType = itemType;
this.roleSupplier = roleSupplier;
}
/**
* Get the required type
*
* @return the required type of the items in the sequence
*/
public ItemType getRequiredType() {
return requiredItemType;
}
@Override
protected OperandRole getOperandRole() {
return OperandRole.SAME_FOCUS_ACTION;
}
/**
* Get the RoleLocator (used to construct error messages)
*
* @return the RoleLocator
*/
public RoleDiagnostic getRoleLocator() {
return roleSupplier.get();
}
/**
* Simplify an expression
*
*/
/*@NotNull*/
@Override
public Expression simplify() throws XPathException {
Expression operand = getBaseExpression().simplify();
if (requiredItemType instanceof AnyItemType) {
return operand;
}
setBaseExpression(operand);
return this;
}
/**
* Type-check the expression
*/
/*@NotNull*/
@Override
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
getOperand().typeCheck(visitor, contextInfo);
Expression operand = getBaseExpression();
if (operand instanceof Block) {
// Do the item-checking on each operand of the block separately (it might not be needed on all items)
// This is particularly needed for streamability analysis of xsl:map
Block block = (Block)operand;
List checkedOperands = new ArrayList<>();
for (Operand o : block.operands()) {
ItemChecker checkedOp = new ItemChecker(o.getChildExpression(), requiredItemType, roleSupplier);
checkedOperands.add(checkedOp);
}
Block newBlock = new Block(checkedOperands.toArray(new Expression[0]));
ExpressionTool.copyLocationInfo(this, newBlock);
return newBlock.typeCheck(visitor, contextInfo);
}
// When typeCheck is called a second time, we might have more information...
final TypeHierarchy th = getConfiguration().getTypeHierarchy();
int card = operand.getCardinality();
if (card == StaticProperty.EMPTY) {
//value is always empty, so no item checking needed
return operand;
}
ItemType supplied = operand.getItemType();
Affinity relation = th.relationship(requiredItemType, supplied);
if (relation == Affinity.SAME_TYPE || relation == Affinity.SUBSUMES) {
return operand;
} else if (relation == Affinity.DISJOINT) {
if (Cardinality.allowsZero(card)) {
if (!(operand instanceof Literal)) {
RoleDiagnostic role = roleSupplier.get();
String message = role.composeErrorMessage(
requiredItemType, operand, th);
visitor.getStaticContext().issueWarning(
"The only value that can pass type-checking is an empty sequence. " +
message, SaxonErrorCode.SXWN9026, getLocation());
}
} else {
RoleDiagnostic role = roleSupplier.get();
String message = role.composeErrorMessage(requiredItemType, operand, th);
throw new XPathException(message)
.withErrorCode(role.getErrorCode())
.withLocation(this.getLocation())
.asTypeErrorIf(role.isTypeError());
}
}
return this;
}
/**
* Perform optimisation of an expression and its subexpressions.
* This method is called after all references to functions and variables have been resolved
* to the declaration of the function or variable, and after all type checking has been done.
*
* @param visitor an expression visitor
* @param contextInfo the static type of "." at the point where this expression is invoked.
* The parameter is set to null if it is known statically that the context item will be undefined.
* If the type of the context item is not known statically, the argument is set to
* {@link Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws XPathException if an error is discovered during this phase
* (typically a type error)
*/
@Override
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
getOperand().optimize(visitor, contextInfo);
TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
Affinity rel = th.relationship(requiredItemType, getBaseExpression().getItemType());
if (rel == Affinity.SAME_TYPE || rel == Affinity.SUBSUMES) {
return getBaseExpression();
}
return this;
}
/**
* An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
* This method indicates which of these methods is provided. This implementation provides both iterate() and
* process() methods natively.
*/
@Override
public int getImplementationMethod() {
int m = ITERATE_METHOD | PROCESS_METHOD | ITEM_FEED_METHOD;
if (!Cardinality.allowsMany(getCardinality())) {
m |= EVALUATE_METHOD;
}
return m;
}
/**
* Get the (partial) name of a class that supports streaming of this kind of expression
*
* @return the partial name of a class that can be instantiated to provide streaming support in Saxon-EE,
* or null if there is no such class
*/
@Override
public String getStreamerName() {
return "ItemChecker";
}
/**
* For an expression that returns an integer or a sequence of integers, get
* a lower and upper bound on the values of the integers that may be returned, from
* static analysis. The default implementation returns null, meaning "unknown" or
* "not applicable". Other implementations return an array of two IntegerValue objects,
* representing the lower and upper bounds respectively. The values
* UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that
* the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH
* are used to indicate values limited by the size of a string or the size of a sequence.
*
* @return the lower and upper bounds of integer values in the result, or null to indicate
* unknown or not applicable.
*/
/*@Nullable*/
@Override
public IntegerValue[] getIntegerBounds() {
return getBaseExpression().getIntegerBounds();
}
/**
* Iterate over the sequence of values
*/
/*@NotNull*/
@Override
public SequenceIterator iterate(XPathContext context) throws XPathException {
return makeElaborator().elaborateForPull().iterate(context);
}
private SequenceIterator checkSequence(SequenceIterator base, XPathContext context) {
final Expression baseExpr = getBaseExpression();
final TypeHierarchy th = context.getConfiguration().getTypeHierarchy();
Consumer- checker = item -> {
if (!requiredItemType.matches(item, th)) {
RoleDiagnostic role = roleSupplier.get();
String message = role.composeErrorMessage(requiredItemType, item, th);
String errorCode = role.getErrorCode();
XPathException te = new XPathException(message, errorCode)
.withFailingExpression(baseExpr)
.withLocation(baseExpr.getLocation())
.asTypeErrorIf(!"XPDY0050".equals(errorCode));
throw new UncheckedXPathException(te);
}
};
return new ItemCheckingIterator(base, checker);
}
/**
* Evaluate as an Item.
*/
@Override
public Item evaluateItem(XPathContext context) throws XPathException {
return makeElaborator().elaborateForItem().eval(context);
}
public Item checkItem(Item item, XPathContext context) throws XPathException {
final TypeHierarchy th = context.getConfiguration().getTypeHierarchy();
if (item == null) {
return null;
}
if (requiredItemType.matches(item, th)) {
return item;
} else {
RoleDiagnostic role = roleSupplier.get();
String message = role.composeErrorMessage(requiredItemType, item, th);
String errorCode = role.getErrorCode();
if ("XPDY0050".equals(errorCode)) {
// error in "treat as" assertion
dynamicError(message, errorCode, context);
} else {
typeError(message, errorCode, context);
}
return null;
}
}
/**
* Process the instruction, without returning any tail calls
*
* @param output the destination for the result
* @param context The dynamic context, giving access to the current node,
*/
@Override
public void process(Outputter output, XPathContext context) throws XPathException {
dispatchTailCall(makeElaborator().elaborateForPush().processLeavingTail(output, context));
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
* @param rebindings variable bindings that need to be changed
*/
/*@NotNull*/
@Override
public Expression copy(RebindingMap rebindings) {
ItemChecker exp = new ItemChecker(getBaseExpression().copy(rebindings), requiredItemType, roleSupplier);
ExpressionTool.copyLocationInfo(this, exp);
return exp;
}
/**
* Determine the data type of the items returned by the expression
*/
/*@NotNull*/
@Override
public ItemType getItemType() {
ItemType operandType = getBaseExpression().getItemType();
TypeHierarchy th = getConfiguration().getTypeHierarchy();
Affinity relationship = th.relationship(requiredItemType, operandType);
switch (relationship) {
case OVERLAPS:
if (requiredItemType instanceof NodeTest && operandType instanceof NodeTest) {
return new CombinedNodeTest((NodeTest) requiredItemType, Token.INTERSECT, (NodeTest) operandType);
} else {
// we don't know how to intersect atomic types, it doesn't actually happen
return requiredItemType;
}
case SUBSUMES:
case SAME_TYPE:
// shouldn't happen, but it doesn't matter
return operandType;
case SUBSUMED_BY:
default:
return requiredItemType;
}
}
/**
* Get the static type of the expression as a UType, following precisely the type
* inference rules defined in the XSLT 3.0 specification.
*
* @return the static item type of the expression according to the XSLT 3.0 defined rules
* @param contextItemType the type of the context item
*/
@Override
public UType getStaticUType(UType contextItemType) {
return UType.fromTypeCode(requiredItemType.getPrimitiveType());
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
requiredItemType == ((ItemChecker) other).requiredItemType;
}
/**
* get HashCode for comparing two expressions. Note that this hashcode gives the same
* result for (A op B) and for (B op A), whether or not the operator is commutative.
*/
@Override
protected int computeHashCode() {
return super.computeHashCode() ^ requiredItemType.hashCode();
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
@Override
public void export(ExpressionPresenter out) throws XPathException {
out.startElement("treat", this);
out.emitAttribute("as", AlphaCode.fromItemType(requiredItemType));
out.emitAttribute("diag", roleSupplier.get().save());
getBaseExpression().export(out);
out.endElement();
}
/**
* Get a name identifying the kind of expression, in terms meaningful to a user.
*
* @return a name identifying the kind of expression, in terms meaningful to a user.
* The name will always be in the form of a lexical XML QName, and should match the name used
* in explain() output displaying the expression.
*/
@Override
public String getExpressionName() {
return "treatAs";
}
/**
* The toString() method for an expression attempts to give a representation of the expression
* in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
* In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
*/
public String toString() {
String typeDesc = requiredItemType.toString();
return "(" + getBaseExpression() + ") treat as " + typeDesc;
}
@Override
public String toShortString() {
return getBaseExpression().toShortString();
}
/**
* Make an elaborator for this expression
*
* @return a suitable elaborator
*/
@Override
public Elaborator getElaborator() {
return new ItemCheckerElaborator();
}
/**
* Elaborator for a {@code treat as} expression, which is usually system-generated by
* the type checking phase of the compiler
*/
public static class ItemCheckerElaborator extends PullElaborator {
@Override
public PullEvaluator elaborateForPull() {
ItemChecker exp = (ItemChecker) getExpression();
Expression arg = exp.getBaseExpression();
PullEvaluator argEval = arg.makeElaborator().elaborateForPull();
return context -> exp.checkSequence(argEval.iterate(context), context);
}
@Override
public ItemEvaluator elaborateForItem() {
ItemChecker expr = (ItemChecker) getExpression();
Expression arg = expr.getBaseExpression();
ItemEvaluator argEval = arg.makeElaborator().elaborateForItem();
return context -> expr.checkItem(argEval.eval(context), context);
}
@Override
public PushEvaluator elaborateForPush() {
ItemChecker expr = (ItemChecker) getExpression();
Expression arg = expr.getBaseExpression();
int card = StaticProperty.ALLOWS_ZERO_OR_MORE;
if (arg instanceof CardinalityChecker) {
card = ((CardinalityChecker) arg).getRequiredCardinality();
arg = ((CardinalityChecker) arg).getBaseExpression();
}
if ((arg.getImplementationMethod() & PROCESS_METHOD) != 0 && !(expr.requiredItemType instanceof DocumentNodeTest)) {
Expression finalArg = arg;
int finalCard = card;
return (output, context) -> {
PushEvaluator argPush = finalArg.makeElaborator().elaborateForPush();
TypeCheckingFilter filter = new TypeCheckingFilter(output);
filter.setRequiredType(expr.requiredItemType, finalCard, expr.roleSupplier.get(), expr.getLocation());
TailCall tc = argPush.processLeavingTail(filter, context);
Expression.dispatchTailCall(tc);
filter.finalCheck();
return null;
};
} else {
// Force pull-mode evaluation
PullEvaluator argEval = arg.makeElaborator().elaborateForPull();
return (output, context) -> {
SequenceIterator iter = expr.checkSequence(argEval.iterate(context), context);
for (Item item; (item = iter.next()) != null; ) {
output.append(item);
}
return null;
};
}
}
}
}
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