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java: enforce non-blank @CopilotToolParam description at compile time #1980

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java: enforce non-blank @CopilotToolParam description at compile time #1980

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18 changes: 18 additions & 0 deletions java/src/main/java/com/github/copilot/tool/CopilotToolProcessor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,24 @@ public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment
}
}
}

// Validate blank @CopilotToolParam descriptions (exempt single-record wrappers)
boolean isSingleRecordWrapper = schemaParameters.size() == 1 && isRecord(schemaParameters.get(0).asType());
for (VariableElement param : schemaParameters) {
if (isSingleRecordWrapper && param.equals(schemaParameters.get(0))) {
continue;
}
CopilotToolParam paramAnnotation = param.getAnnotation(CopilotToolParam.class);
if (paramAnnotation != null && paramAnnotation.value().isBlank()) {
TypeElement enclosingClass = (TypeElement) method.getEnclosingElement();
processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR,
"@CopilotToolParam on parameter '" + param.getSimpleName() + "' in '"
+ enclosingClass.getSimpleName() + "." + method.getSimpleName()
+ "' has a blank value (description). "
+ "Descriptions are required so the LLM can correctly select and invoke the tool",
param);
}
}
}

// Group methods by enclosing type
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100 changes: 100 additions & 0 deletions java/src/test/java/com/github/copilot/tool/CopilotToolProcessorTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -189,6 +189,106 @@ public String search(@CopilotToolParam(value = "Search input", required = false,
"Expected compile error for single-record wrapper metadata overrides, got: " + result.diagnostics);
}

// ── Test: Blank @CopilotToolParam description validation ────────────────────

@Test
void emitsError_forBlankParamDescription() {
String source = """
package test;
import com.github.copilot.tool.CopilotTool;
import com.github.copilot.tool.CopilotToolParam;
public class BlankDescTools {
@CopilotTool("Search for items")
public String searchItems(@CopilotToolParam("") String query) {
return "results for " + query;
}
}
""";

CompilationResult result = compileWithProcessor(List.of(inMemorySource("test.BlankDescTools", source)));

assertTrue(hasErrorContaining(result, "blank value (description)"),
"Expected compile error for blank @CopilotToolParam description, got: " + result.diagnostics);
}

@Test
void emitsError_forWhitespaceOnlyParamDescription() {
String source = """
package test;
import com.github.copilot.tool.CopilotTool;
import com.github.copilot.tool.CopilotToolParam;
public class WhitespaceDescTools {
@CopilotTool("Search for items")
public String searchItems(@CopilotToolParam(" ") String query) {
return "results for " + query;
}
}
""";

CompilationResult result = compileWithProcessor(List.of(inMemorySource("test.WhitespaceDescTools", source)));

assertTrue(hasErrorContaining(result, "blank value (description)"),
"Expected compile error for whitespace-only @CopilotToolParam description, got: " + result.diagnostics);
}

@Test
void compilesSuccessfully_forValidParamDescription() {
String source = """
package test;
import com.github.copilot.tool.CopilotTool;
import com.github.copilot.tool.CopilotToolParam;
public class ValidDescTools {
@CopilotTool("Search for items")
public String searchItems(@CopilotToolParam("Search query") String query) {
return "results for " + query;
}
}
""";

CompilationResult result = compileWithProcessor(List.of(inMemorySource("test.ValidDescTools", source)));

assertNoErrors(result);
}

@Test
void compilesSuccessfully_forParamWithoutAnnotation() {
String source = """
package test;
import com.github.copilot.tool.CopilotTool;
public class NoAnnotationTools {
@CopilotTool("Search for items")
public String searchItems(String query) {
return "results for " + query;
}
}
""";

CompilationResult result = compileWithProcessor(List.of(inMemorySource("test.NoAnnotationTools", source)));

assertNoErrors(result);
}

@Test
void doesNotEmitBlankError_forSingleRecordWrapperWithDefaultAnnotation() {
String source = """
package test;
import com.github.copilot.tool.CopilotTool;
import com.github.copilot.tool.CopilotToolParam;
public class RecordWrapperTools {
public record SearchArgs(String query, int limit) {}
@CopilotTool("Search for items")
public String search(@CopilotToolParam SearchArgs args) {
return args.query();
}
}
""";

CompilationResult result = compileWithProcessor(List.of(inMemorySource("test.RecordWrapperTools", source)));

assertFalse(hasErrorContaining(result, "blank value (description)"),
"Single-record wrapper should be exempt from blank description check, got: " + result.diagnostics);
}

// ── Test: Return type handling ──────────────────────────────────────────────

@Test
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