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Return empty string for un-evaluated lazy expression. #405

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merged 2 commits into from
Feb 28, 2020
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Return empty string for un-evaluated lazy expression. #405

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35bb0de
Return empty string for un-evaluated lazy expression.
hs-lsong Feb 28, 2020
7c73374
Revert the style check.
hs-lsong Feb 28, 2020
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13 changes: 10 additions & 3 deletions src/main/java/com/hubspot/jinjava/interpret/LazyExpression.java
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Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,9 @@
import com.fasterxml.jackson.annotation.JsonValue;

public class LazyExpression implements Supplier {

private final Supplier supplier;
private final String image;
private Object jsonValue = null;

private LazyExpression(Supplier supplier, String image) {
this.supplier = supplier;
Expand All @@ -19,13 +19,20 @@ public static LazyExpression of(Supplier supplier, String image) {
}

@Override
@JsonValue
public Object get() {
return supplier.get();
if (jsonValue == null) {
jsonValue = supplier.get();
}
return jsonValue;
}

@Override
public String toString() {
return image;
}

@JsonValue
public Object getJsonValue() {
return jsonValue == null ? "" : jsonValue;
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Could it evaluate the supplier but catch any exception and return empty string?

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That is a good question. It depends what the serialization wants. What I wanted here is to get the current state -- no more evaluation. Maybe there is a need to finalize any un-evaluated expression.

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LazyExpression was created as a more under-the-hood optimization where we could use it to prevent computing something if it wasn't needed. It would be still useful to compute when debugging information.

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When debugging, you either just use the toString(), and/or with get() to evaluate it.

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I am talking from the developer perspective. Developers depend on the developer info button that displays the context.

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How does it work now? It will throw exceptions for serialization. If it is not using the json serialization, it does not affect anything.

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I think the serialization breaks if the get() method throws an exception (in the case of the NPE). We should also at least fall back on the image property.

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I assume when we store the lazyExpression in somewhere, we assume to store the value, only when we need it. However, the serialization should not execute the function because it may have side effect -- which may cause concurrent modification exception. I thought the image is the expression itself. I think they should be evaluate to empty, but I am OK if you change to keep it.

}
}
22 changes: 18 additions & 4 deletions src/test/java/com/hubspot/jinjava/interpret/LazyExpressionTest.java
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Expand Up @@ -2,17 +2,31 @@

import static org.assertj.core.api.Assertions.assertThat;

import org.junit.Test;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.collect.ImmutableMap;
import org.junit.Test;

public class LazyExpressionTest {

@Test
public void itSerializesUnderlyingValue() throws JsonProcessingException {
LazyExpression expression = LazyExpression.of(() -> ImmutableMap.of("test", "hello", "test2", "hello2"), "{}");
assertThat(new ObjectMapper().writeValueAsString(expression)).isEqualTo("{\"test\":\"hello\",\"test2\":\"hello2\"}");
LazyExpression expression = LazyExpression.of(
() -> ImmutableMap.of("test", "hello", "test2", "hello2"),
"{}"
);
Object evaluated = expression.get();
assertThat(evaluated).isNotNull();
assertThat(new ObjectMapper().writeValueAsString(expression))
.isEqualTo("{\"test\":\"hello\",\"test2\":\"hello2\"}");
}

@Test
public void itSerializesNonEvaluatedValueToEmpty() throws JsonProcessingException {
LazyExpression expression = LazyExpression.of(
() -> ImmutableMap.of("test", "hello", "test2", "hello2"),
"{}"
);
assertThat(new ObjectMapper().writeValueAsString(expression)).isEqualTo("\"\"");
}
}
2 changes: 1 addition & 1 deletion src/test/java/com/hubspot/jinjava/lib/fn/UnixTimestampFunctionTest.java
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Expand Up @@ -13,7 +13,7 @@ public class UnixTimestampFunctionTest {

@Test
public void itGetsUnixTimestamps() {
assertThat(Functions.unixtimestamp()).isGreaterThan(0).isLessThan(System.currentTimeMillis());
assertThat(Functions.unixtimestamp()).isGreaterThan(0).isLessThanOrEqualTo(System.currentTimeMillis());
assertThat(Functions.unixtimestamp(epochMilliseconds)).isEqualTo(epochMilliseconds);
assertThat(Functions.unixtimestamp(d)).isEqualTo(epochMilliseconds);
assertThat(Math.abs(Functions.unixtimestamp(null) - ZonedDateTime.now().toEpochSecond() * 1000)).isLessThan(1000);
Expand Down