opendev/gerrit
Code Issues Proposed changes

Gracefully fail when submit_rule/1 has no solutions

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If a submit_rule is coded with no solution for a change, e.g.:

  submit_rule(submit()) :- fail.

the server used to crash with 500s from a number of REST APIs,
caused by a ClassCastException inside of SubmitRuleEvaluator.

An empty result list is not a ListTerm, it is a SymbolTerm and using
the NIL instance '[]'. This cannot be cast to a ListTerm for return
to the caller.

Instead return List<Term> and handle the conversion, ensuring an
empty list is returned to callers when there are no results.

Change-Id: Iea1211afb2f3970ba98ea1eff14df07452cf5ccd
This commit is contained in:
Shawn Pearce
2013-04-19 10:25:39 -07:00
parent f3388c0ec0
commit 23050e196c
4 changed files with 32 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
gerrit-server/src/main/java/com/google/gerrit/server/project/SubmitRuleEvaluator.java
View File

@@ -14,6 +14,7 @@
package com.google.gerrit.server.project;
import com.google.common.collect.Lists;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.gerrit.reviewdb.server.ReviewDb;
@@ -30,6 +31,7 @@ import com.googlecode.prolog_cafe.lang.VariableTerm;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.annotation.Nullable;
@@ -124,8 +126,7 @@ public class SubmitRuleEvaluator {
* @return List of {@link Term} objects returned from the evaluated rules.
* @throws RuleEvalException
*/
public ListTerm evaluate() throws RuleEvalException {
List<Term> results = new ArrayList<Term>();
public List<Term> evaluate() throws RuleEvalException {
PrologEnvironment env = getPrologEnvironment();
try {
submitRule = env.once("gerrit", userRuleLocatorName, new VariableTerm());
@@ -133,6 +134,7 @@ public class SubmitRuleEvaluator {
env.once("gerrit", "assume_range_from_label");
}
List<Term> results = new ArrayList<Term>();
try {
for (Term[] template : env.all("gerrit", userRuleWrapperName,
submitRule, new VariableTerm())) {
@@ -152,7 +154,16 @@ public class SubmitRuleEvaluator {
if (!skipFilters) {
resultsTerm = runSubmitFilters(resultsTerm, env);
}
return (ListTerm) resultsTerm;
if (resultsTerm.isList()) {
List<Term> r = Lists.newArrayList();
for (Term t = resultsTerm; t.isList();) {
ListTerm l = (ListTerm) t;
r.add(l.car().dereference());
t = l.cdr().dereference();
}
return r;
}
return Collections.emptyList();
} finally {
env.close();
}