No longer crash when running "bazel help <rule>".

Fixes #2270.

--
PiperOrigin-RevId: 150324978
MOS_MIGRATED_REVID=150324978

1 files changed, 7 insertions, 6 deletions

diff --git a/src/main/java/com/google/devtools/build/docgen/BlazeRuleHelpPrinter.java b/src/main/java/com/google/devtools/build/docgen/BlazeRuleHelpPrinter.java
index e262aa4267..789554f312 100644
--- a/src/main/java/com/google/devtools/build/docgen/BlazeRuleHelpPrinter.java
+++ b/src/main/java/com/google/devtools/build/docgen/BlazeRuleHelpPrinter.java
@@ -13,10 +13,8 @@
 // limitations under the License.
 package com.google.devtools.build.docgen;
 
-import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
-
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
@@ -50,10 +48,13 @@ public class BlazeRuleHelpPrinter {
         return e.getMessage();
       }
     }
-    // Every rule should be documented and this method should be called only
-    // for existing rules (a check is performed in HelpCommand).
-    Preconditions.checkState(ruleDocMap.containsKey(ruleName), String.format(
-        "ERROR: Documentation of rule %s does not exist.", ruleName));
+    // TODO(fwe): generate the rule documentation when building the Bazel binary and ship
+    // the text documentation with the binary.
+    // The Bazel binary may not contain the rule sources, which means that the documentation
+    // retrieval step would fail with an exception.
+    if (!ruleDocMap.containsKey(ruleName)) {
+      return String.format("Documentation for rule %s is not part of the binary.\n", ruleName);
+    }
     return "Rule " + ruleName + ":"
         + ruleDocMap.get(ruleName).getCommandLineDocumentation() + "\n";
   }