src/main/java/com/google/devtools/build/lib/syntax/EvalExceptionWithStackTrace.java - bazel - Git at Google

 // Copyright 2015 The Bazel Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //    http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 package com.google.devtools.build.lib.syntax;

 import com.google.common.base.Joiner;
 import com.google.common.base.Preconditions;
 import com.google.devtools.build.lib.events.Location;
 import java.util.Deque;
 import java.util.LinkedList;

 /**
  * EvalException with a stack trace.
  */
 public class EvalExceptionWithStackTrace extends EvalException {

   private StackFrame mostRecentElement;

   public EvalExceptionWithStackTrace(Exception original, Node culprit) {
     super(extractLocation(original, culprit), getNonEmptyMessage(original), getCause(original));
     registerNode(culprit);
   }

   @Override
   public boolean canBeAddedToStackTrace() {
     // Doesn't make any sense to add this exception to another instance of
     // EvalExceptionWithStackTrace.
     return false;
   }

   /**
    * Returns the appropriate location for this exception.
    *
    * <p>If the {@code Node} is non-null, its location is used. Otherwise, we try to get the location
    * of the exception.
    */
   private static Location extractLocation(Exception original, Node culprit) {
     if (culprit != null) {
       return culprit.getStartLocation();
     }
     return original instanceof EvalException ? ((EvalException) original).getLocation() : null;
   }

   /**
    * Returns the "real" cause of this exception.
    *
    * <p>If the original exception is an EvalException, its cause is returned.
    * Otherwise, the original exception itself is seen as the cause for this exception.
    */
   private static Throwable getCause(Exception ex) {
     return (ex instanceof EvalException) ? ex.getCause() : ex;
   }

   /** Adds an entry for the given {@code Node} to the stack trace. */
   public void registerNode(Node node) {
     addStackFrame(node.toString().trim(), node.getStartLocation());
   }

   /**
    * Makes sure the stack trace is rooted in a function call.
    *
    * <p>In some cases (rule implementation application, aspect implementation application) bazel
    * calls into the function directly (using BaseFunction.call). In that case, since there is no
    * CallExpression to evaluate, stack trace mechanism cannot record this call. This method allows
    * to augument the stack trace with information about the call.
    */
   public void registerPhantomCall(
       String callDescription, Location location, BaseFunction function) {
     /*
      *
      * We add two new frames to the stack:
      * 1. Pseudo-function call (for example, rule definition)
      * 2. Function entry (Rule implementation)
      *
      * Similar to Python, all functions that were entered (except for the top-level ones) appear
      * twice in the stack trace output. This would lead to the following trace:
      *
      * File BUILD, line X, in <module>
      *     rule_definition()
      * File BUILD, line X, in rule_definition
      *     rule_implementation()
      * File bzl, line Y, in rule_implementation
      *     ...
      *
      * Please note that lines 3 and 4 are quite confusing since a) the transition from
      * rule_definition to rule_implementation happens internally and b) the locations do not make
      * any sense.
      * Consequently, we decided to omit lines 3 and 4 from the output via canPrint = false:
      *
      * File BUILD, line X, in <module>
      *     rule_definition()
      * File bzl, line Y, in rule_implementation
      *     ...
      *
      * */
     addStackFrame(function.getName(), function.getLocation());
     addStackFrame(callDescription, location, false);
   }

   /** Adds a line for the given frame. */
   private void addStackFrame(String label, Location location, boolean canPrint) {
     // TODO(bazel-team): This check was originally created to weed out duplicates in case the same
     // node is added twice, but it's not clear if that is still a possibility. In any case, it would
     // be better to eliminate the check and not create unwanted duplicates in the first place.
     //
     // The check is problematic because it suppresses tracebacks in the REPL, where line numbers
     // can be reset within a single session.
     if (mostRecentElement != null && location.equals(mostRecentElement.getLocation())) {
       return;
     }
     mostRecentElement = new StackFrame(label, location, mostRecentElement, canPrint);
   }

   private void addStackFrame(String label, Location location)   {
     addStackFrame(label, location, true);
   }

   /**
    * Returns the exception message without the stack trace.
    */
   public String getOriginalMessage() {
     return super.getMessage();
   }

   @Override
   public String getMessage() {
     return print();
   }

   @Override
   public String print() {
     // Currently, we do not limit the text length per line.
     return print(StackTracePrinter.INSTANCE);
   }

   /**
    *  Prints the stack trace iff it contains more than just one built-in function.
    */
   public String print(StackTracePrinter printer) {
     return canPrintStackTrace()
         ? printer.print(getOriginalMessage(), mostRecentElement)
         : getOriginalMessage();
   }

   /**
    * Returns true when there is at least one non-built-in element.
    */
   protected boolean canPrintStackTrace() {
     return mostRecentElement != null && mostRecentElement.getCause() != null;
   }

   /**
    * An element in the stack trace which contains the name of the offending function / rule /
    * statement and its location.
    */
   protected static final class StackFrame {
     private final String label;
     private final Location location;
     private final StackFrame cause;
     private final boolean canPrint;

     StackFrame(String label, Location location, StackFrame cause, boolean canPrint) {
       this.label = label;
       this.location = location;
       this.cause = cause;
       this.canPrint = canPrint;
     }

     String getLabel() {
       return label;
     }

     Location getLocation() {
       return location;
     }

     StackFrame getCause() {
       return cause;
     }

     boolean canPrint() {
       return canPrint;
     }

     @Override
     public String toString() {
       return String.format("%s @ %s -> %s", label, location, String.valueOf(cause));
     }
   }

   /**
    * Singleton class that prints stack traces similar to Python.
    */
   public enum StackTracePrinter {
     INSTANCE;

     /**
      * Turns the given message and StackTraceElements into a string.
      */
     public final String print(String message, StackFrame mostRecentElement) {
       Deque<String> output = new LinkedList<>();

       // Adds dummy element for the rule call that uses the location of the top-most function.
       mostRecentElement = new StackFrame("", mostRecentElement.getLocation(),
           (mostRecentElement.getCause() == null) ? null : mostRecentElement, true);

       while (mostRecentElement != null) {
         if (mostRecentElement.canPrint()) {
           String entry = print(mostRecentElement);
           if (entry != null && entry.length() > 0) {
             addEntry(output, entry);
           }
         }

         mostRecentElement = mostRecentElement.getCause();
       }

       addMessage(output, message);
       return Joiner.on(System.lineSeparator()).join(output);
     }

     /** Returns the string representation of the given element. */
     protected String print(StackFrame element) {
       // Similar to Python, the first (most-recent) entry in the stack frame is printed only once.
       // Consequently, we skip it here.
       if (element.getCause() == null) {
         return "";
       }

       // Prints a two-line string, similar to Python.
       Location location = getLocation(element.getCause());
       return String.format(
           "\tFile \"%s\", line %d%s%n\t\t%s",
           printPath(location),
           getLine(location),
           printFunction(element.getLabel()),
           element.getCause().getLabel());
     }

     /** Returns the location of the given element or Location.BUILTIN if the element is null. */
     private Location getLocation(StackFrame element) {
       return (element == null) ? Location.BUILTIN : element.getLocation();
     }

     private String printFunction(String func) {
       if (func.isEmpty()) {
         return "";
       }

       int pos = func.indexOf('(');
       return String.format(", in %s", (pos < 0) ? func : func.substring(0, pos));
     }

     private String printPath(Location loc) {
       return loc == null ? "<unknown>" : loc.file();
     }

     private int getLine(Location loc) {
       return loc == null ? 0 : loc.line();
     }

     /**
      * Adds the given string to the specified Deque.
      */
     protected void addEntry(Deque<String> output, String toAdd) {
       output.addLast(toAdd);
     }

     /**
      * Adds the given message to the given output dequeue after all stack trace elements have been
      * added.
      */
     protected void addMessage(Deque<String> output, String message) {
       output.addFirst("Traceback (most recent call last):");
       output.addLast(message);
     }
   }

   /**
    * Returns a non-empty message for the given exception.
    *
    * <p> If the exception itself does not have a message, a new message is constructed from the
    * exception's class name.
    * For example, an IllegalArgumentException will lead to "Illegal Argument".
    * Additionally, the location in the Java code will be added, if applicable,
    */
   private static String getNonEmptyMessage(Exception original) {
     Preconditions.checkNotNull(original);
     String msg = original.getMessage();
     if (msg != null && !msg.isEmpty()) {
       return msg;
     }

     char[] name = original.getClass().getSimpleName().replace("Exception", "").toCharArray();
     boolean first = true;
     StringBuilder builder = new StringBuilder();

     for (char current : name) {
       if (Character.isUpperCase(current) && !first) {
         builder.append(" ");
       }
       builder.append(current);
       first = false;
     }

     java.lang.StackTraceElement[] trace = original.getStackTrace();
     if (trace.length > 0) {
       builder.append(String.format(": %s.%s() in %s:%d", getShortClassName(trace[0]),
           trace[0].getMethodName(), trace[0].getFileName(), trace[0].getLineNumber()));
     }

     return builder.toString();
   }

   private static String getShortClassName(java.lang.StackTraceElement element) {
     String name = element.getClassName();
     int pos = name.lastIndexOf('.');
     return (pos < 0) ? name : name.substring(pos + 1);
   }
 }
	// Copyright 2015 The Bazel Authors. All rights reserved.
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.
	package com.google.devtools.build.lib.syntax;

	import com.google.common.base.Joiner;
	import com.google.common.base.Preconditions;
	import com.google.devtools.build.lib.events.Location;
	import java.util.Deque;
	import java.util.LinkedList;

	/**
	* EvalException with a stack trace.
	*/
	public class EvalExceptionWithStackTrace extends EvalException {

	private StackFrame mostRecentElement;

	public EvalExceptionWithStackTrace(Exception original, Node culprit) {
	super(extractLocation(original, culprit), getNonEmptyMessage(original), getCause(original));
	registerNode(culprit);
	}

	@Override
	public boolean canBeAddedToStackTrace() {
	// Doesn't make any sense to add this exception to another instance of
	// EvalExceptionWithStackTrace.
	return false;
	}

	/**
	* Returns the appropriate location for this exception.
	*
	* <p>If the {@code Node} is non-null, its location is used. Otherwise, we try to get the location
	* of the exception.
	*/
	private static Location extractLocation(Exception original, Node culprit) {
	if (culprit != null) {
	return culprit.getStartLocation();
	}
	return original instanceof EvalException ? ((EvalException) original).getLocation() : null;
	}

	/**
	* Returns the "real" cause of this exception.
	*
	* <p>If the original exception is an EvalException, its cause is returned.
	* Otherwise, the original exception itself is seen as the cause for this exception.
	*/
	private static Throwable getCause(Exception ex) {
	return (ex instanceof EvalException) ? ex.getCause() : ex;
	}

	/** Adds an entry for the given {@code Node} to the stack trace. */
	public void registerNode(Node node) {
	addStackFrame(node.toString().trim(), node.getStartLocation());
	}

	/**
	* Makes sure the stack trace is rooted in a function call.
	*
	* <p>In some cases (rule implementation application, aspect implementation application) bazel
	* calls into the function directly (using BaseFunction.call). In that case, since there is no
	* CallExpression to evaluate, stack trace mechanism cannot record this call. This method allows
	* to augument the stack trace with information about the call.
	*/
	public void registerPhantomCall(
	String callDescription, Location location, BaseFunction function) {
	/*
	*
	* We add two new frames to the stack:
	* 1. Pseudo-function call (for example, rule definition)
	* 2. Function entry (Rule implementation)
	*
	* Similar to Python, all functions that were entered (except for the top-level ones) appear
	* twice in the stack trace output. This would lead to the following trace:
	*
	* File BUILD, line X, in <module>
	* rule_definition()
	* File BUILD, line X, in rule_definition
	* rule_implementation()
	* File bzl, line Y, in rule_implementation
	* ...
	*
	* Please note that lines 3 and 4 are quite confusing since a) the transition from
	* rule_definition to rule_implementation happens internally and b) the locations do not make
	* any sense.
	* Consequently, we decided to omit lines 3 and 4 from the output via canPrint = false:
	*
	* File BUILD, line X, in <module>
	* rule_definition()
	* File bzl, line Y, in rule_implementation
	* ...
	*
	* */
	addStackFrame(function.getName(), function.getLocation());
	addStackFrame(callDescription, location, false);
	}

	/** Adds a line for the given frame. */
	private void addStackFrame(String label, Location location, boolean canPrint) {
	// TODO(bazel-team): This check was originally created to weed out duplicates in case the same
	// node is added twice, but it's not clear if that is still a possibility. In any case, it would
	// be better to eliminate the check and not create unwanted duplicates in the first place.
	//
	// The check is problematic because it suppresses tracebacks in the REPL, where line numbers
	// can be reset within a single session.
	if (mostRecentElement != null && location.equals(mostRecentElement.getLocation())) {
	return;
	}
	mostRecentElement = new StackFrame(label, location, mostRecentElement, canPrint);
	}

	private void addStackFrame(String label, Location location) {
	addStackFrame(label, location, true);
	}

	/**
	* Returns the exception message without the stack trace.
	*/
	public String getOriginalMessage() {
	return super.getMessage();
	}

	@Override
	public String getMessage() {
	return print();
	}

	@Override
	public String print() {
	// Currently, we do not limit the text length per line.
	return print(StackTracePrinter.INSTANCE);
	}

	/**
	* Prints the stack trace iff it contains more than just one built-in function.
	*/
	public String print(StackTracePrinter printer) {
	return canPrintStackTrace()
	? printer.print(getOriginalMessage(), mostRecentElement)
	: getOriginalMessage();
	}

	/**
	* Returns true when there is at least one non-built-in element.
	*/
	protected boolean canPrintStackTrace() {
	return mostRecentElement != null && mostRecentElement.getCause() != null;
	}

	/**
	* An element in the stack trace which contains the name of the offending function / rule /
	* statement and its location.
	*/
	protected static final class StackFrame {
	private final String label;
	private final Location location;
	private final StackFrame cause;
	private final boolean canPrint;

	StackFrame(String label, Location location, StackFrame cause, boolean canPrint) {
	this.label = label;
	this.location = location;
	this.cause = cause;
	this.canPrint = canPrint;
	}

	String getLabel() {
	return label;
	}

	Location getLocation() {
	return location;
	}

	StackFrame getCause() {
	return cause;
	}

	boolean canPrint() {
	return canPrint;
	}

	@Override
	public String toString() {
	return String.format("%s @ %s -> %s", label, location, String.valueOf(cause));
	}
	}

	/**
	* Singleton class that prints stack traces similar to Python.
	*/
	public enum StackTracePrinter {
	INSTANCE;

	/**
	* Turns the given message and StackTraceElements into a string.
	*/
	public final String print(String message, StackFrame mostRecentElement) {
	Deque<String> output = new LinkedList<>();

	// Adds dummy element for the rule call that uses the location of the top-most function.
	mostRecentElement = new StackFrame("", mostRecentElement.getLocation(),
	(mostRecentElement.getCause() == null) ? null : mostRecentElement, true);

	while (mostRecentElement != null) {
	if (mostRecentElement.canPrint()) {
	String entry = print(mostRecentElement);
	if (entry != null && entry.length() > 0) {
	addEntry(output, entry);
	}
	}

	mostRecentElement = mostRecentElement.getCause();
	}

	addMessage(output, message);
	return Joiner.on(System.lineSeparator()).join(output);
	}

	/** Returns the string representation of the given element. */
	protected String print(StackFrame element) {
	// Similar to Python, the first (most-recent) entry in the stack frame is printed only once.
	// Consequently, we skip it here.
	if (element.getCause() == null) {
	return "";
	}

	// Prints a two-line string, similar to Python.
	Location location = getLocation(element.getCause());
	return String.format(
	"\tFile \"%s\", line %d%s%n\t\t%s",
	printPath(location),
	getLine(location),
	printFunction(element.getLabel()),
	element.getCause().getLabel());
	}

	/** Returns the location of the given element or Location.BUILTIN if the element is null. */
	private Location getLocation(StackFrame element) {
	return (element == null) ? Location.BUILTIN : element.getLocation();
	}

	private String printFunction(String func) {
	if (func.isEmpty()) {
	return "";
	}

	int pos = func.indexOf('(');
	return String.format(", in %s", (pos < 0) ? func : func.substring(0, pos));
	}

	private String printPath(Location loc) {
	return loc == null ? "<unknown>" : loc.file();
	}

	private int getLine(Location loc) {
	return loc == null ? 0 : loc.line();
	}

	/**
	* Adds the given string to the specified Deque.
	*/
	protected void addEntry(Deque<String> output, String toAdd) {
	output.addLast(toAdd);
	}

	/**
	* Adds the given message to the given output dequeue after all stack trace elements have been
	* added.
	*/
	protected void addMessage(Deque<String> output, String message) {
	output.addFirst("Traceback (most recent call last):");
	output.addLast(message);
	}
	}

	/**
	* Returns a non-empty message for the given exception.
	*
	* <p> If the exception itself does not have a message, a new message is constructed from the
	* exception's class name.
	* For example, an IllegalArgumentException will lead to "Illegal Argument".
	* Additionally, the location in the Java code will be added, if applicable,
	*/
	private static String getNonEmptyMessage(Exception original) {
	Preconditions.checkNotNull(original);
	String msg = original.getMessage();
	if (msg != null && !msg.isEmpty()) {
	return msg;
	}

	char[] name = original.getClass().getSimpleName().replace("Exception", "").toCharArray();
	boolean first = true;
	StringBuilder builder = new StringBuilder();

	for (char current : name) {
	if (Character.isUpperCase(current) && !first) {
	builder.append(" ");
	}
	builder.append(current);
	first = false;
	}

	java.lang.StackTraceElement[] trace = original.getStackTrace();
	if (trace.length > 0) {
	builder.append(String.format(": %s.%s() in %s:%d", getShortClassName(trace[0]),
	trace[0].getMethodName(), trace[0].getFileName(), trace[0].getLineNumber()));
	}

	return builder.toString();
	}

	private static String getShortClassName(java.lang.StackTraceElement element) {
	String name = element.getClassName();
	int pos = name.lastIndexOf('.');
	return (pos < 0) ? name : name.substring(pos + 1);
	}
	}