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https://issues.apache.org/jira/browse/JEXL-323?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Henri Biestro resolved JEXL-323.
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Fix Version/s: 3.2
Assignee: Henri Biestro
Resolution: Fixed
Changeset: ef8a3e3435e2948b2afd7972901eac5a45721b19
Author: henrib <[email protected]>
Date: 2020-01-29 17:57
Message: JEXL-323, JEXL-327: fixed error reporting an null checks
> Ant-style variables can throw exception when evaluated for their value
> ----------------------------------------------------------------------
>
> Key: JEXL-323
> URL: https://issues.apache.org/jira/browse/JEXL-323
> Project: Commons JEXL
> Issue Type: Bug
> Affects Versions: 3.1
> Reporter: David Costanzo
> Assignee: Henri Biestro
> Priority: Minor
> Fix For: 3.2
>
>
> When try to evaluate an expression that is the name of a variable and the
> value is null, I get the value null. This is good. However, when I do the
> same thing with an ant-style variable name, a JexlException$Variable is
> thrown claiming that the variable is null. I think this is a bug because I
> would expect all variables to behave the same, regardless of their name.
> The reason for this behavior is evident in Interpreter.visit() and
> InterpreterBase.unsolvableVariable(). There is already special-case logic to
> detect when an ant variable is null versus when it's undefined, and this
> information is given to unsolvableVariable(), but it still throws an
> exception.
>
> {code:java}
> if (object == null && !isTernaryProtected(node)) {
> if (antish && ant != null) {
> // V--- NOTE: context.has() returns true, so undefined is false
> boolean undefined = !(context.has(ant.toString()) ||
> isLocalVariable(node, 0));
> // variable unknown in context and not a local
> return unsolvableVariable(node, ant.toString(), undefined); //
> <-- still throws exception
> } else if (!pty) {
> return unsolvableProperty(node, "<null>.<?>", null);
> }
> }
> {code}
> In in unsolvableVariable():
>
> {code:java}
> protected Object unsolvableVariable(JexlNode node, String var, boolean undef)
> {
> // V-- NOTE: both my engine and arithmetic are strict, so this evaluates
> to true
> if (isStrictEngine() && (undef || arithmetic.isStrict())) {
> throw new JexlException.Variable(node, var, undef);
> } else if (logger.isDebugEnabled()) {
> logger.debug(JexlException.variableError(node, var, undef));
> }
> return null;
> }
> {code}
>
>
> h3. Steps to Reproduce:
>
> {code:java}
> @Test
> public void testNullAntVariable() throws IOException {
> // Create or retrieve an engine
> JexlEngine jexl = new JexlBuilder().create();
> // on recent code: JexlEngine jexl = new
> JexlBuilder().safe(false).create();
> // Populate to identical global variables
> JexlContext jc = new MapContext();
> jc.set("NormalVariable", null);
> jc.set("ant.variable", null);
> // Evaluate the value of the normal variable
> JexlExpression expression1 = jexl.createExpression("NormalVariable");
> Object o1 = expression1.evaluate(jc);
> Assert.assertEquals(null, o1);
> // Evaluate the value of the ant-style variable
> JexlExpression expression2 = jexl.createExpression("ant.variable");
> Object o2 = expression2.evaluate(jc); // <-- BUG: throws exception
> instead of returning null
> Assert.assertEquals(null, o2);
> }
> {code}
>
>
> h3. What Happens:
> "expression2.evaluate(jc)" throws an JexlException$Variable exception with
> text like "variable 'ant.variable' is null".
> h3. Expected Result:
> expression2.evaluate(jc) returns the value of 'ant.variable', which is null.
> h3.
> Note:
> This was found on JEXL 3.1, the latest official release. I reproduced it on a
> snapshot of JEXL 3.2 built from github source, but had to disable "safe".
> h3.
> Impact:
> My organization uses JEXL to build datasets for clinical trials. In our
> domain, it's very common to have an expression that is simply the name of a
> variable whose value is desired. In our domain, we want any sloppy
> expressions to be a hard error, so we we use strict engines and will use
> "safe=false" when we update to JEXL 3.2. In our domain, "null" has a specific
> meaning (it means "missing"). A missing value is distinct from an "undefined
> variable", which is always an error to reference. Because of this bug, we had
> to ban using "." in names of "global" variables (variables populated in the
> JexlContext).
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