Handle failed process launches at the call sites

With direct argv, a missing or non-executable command now throws from
runProcess(), as its javadoc always documented ('If there is any
problem with the process, throws an exception') - the removed shell
wrapper used to mask launch failures as exit code 127. Handle the
launch failure where graceful failure is the intent:

- SpecsGraphviz: dot being absent is a normal condition, so checkDot()
  returns false and renderDot() logs instead of crashing.
- ProcessExecution: the jobs framework is built on return codes with
  no exception handling, so run() reports the failed launch as
  exit code 127 instead of propagating.

This also restores SpecsSystem.isCommandAvailable()'s intended
behavior: it detects missing commands by catching the launch
exception, which the wrapper's masking previously defeated.

Author: lm-sousa

SpecsUtils/src/pt/up/fe/specs/util/SpecsGraphviz.java

@@ -29,8 +29,13 @@ public class SpecsGraphviz {
     private static final Lazy<Boolean> IS_DOT_AVAILABLE = Lazy.newInstance(SpecsGraphviz::checkDot);
 
     private static boolean checkDot() {
-        var result = SpecsSystem.runProcess(Arrays.asList("dot", "-?"), false, false);
-        return result.getReturnValue() == 0;
+        try {
+            var result = SpecsSystem.runProcess(Arrays.asList("dot", "-?"), false, false);
+            return result.getReturnValue() == 0;
+        } catch (RuntimeException e) {
+            // The launch itself failed, e.g. Graphviz is not installed
+            return false;
+        }
     }
 
     public static boolean isDotAvailable() {
@@ -47,9 +52,19 @@ public static void renderDot(File dotFile, DotRenderFormat format, File outputFi
         var command = Arrays.asList("dot", format.getFlag(), dotFile.getAbsolutePath(), "-o",
                 outputFile.getAbsolutePath());
 
-        var result = SpecsSystem.runProcess(command, false, false);
-        if (result.getReturnValue() == 0) {
-            SpecsLogs.debug(() -> "Rendered dot file '" + dotFile.getAbsolutePath() + "' as " + format);
+        try {
+            var result = SpecsSystem.runProcess(command, false, false);
+            if (result.getReturnValue() == 0) {
+                SpecsLogs.debug(() -> "Rendered dot file '" + dotFile.getAbsolutePath() + "' as " + format);
+            }
+        } catch (RuntimeException e) {
+            // Only a missing Graphviz installation is skipped; any other
+            // failure is rethrown
+            if (!SpecsSystem.isLaunchFailure(e)) {
+                throw e;
+            }
+
+            SpecsLogs.msgInfo("Graphviz not available, could not render dot file '" + dotFile.getAbsolutePath() + "'");
         }
     }
 

SpecsUtils/src/pt/up/fe/specs/util/SpecsSystem.java

@@ -578,6 +578,26 @@ public static boolean isCommandAvailable(List<String> command, File workingdir)
 
     }
 
+    /**
+     * Checks if the throwable was caused by a failure to launch the process
+     * itself (e.g., command not found or not executable), as opposed to a
+     * failure after a successful launch.
+     *
+     * @param throwable
+     * @return
+     */
+    public static boolean isLaunchFailure(Throwable throwable) {
+        for (Throwable currentThrowable = throwable; currentThrowable != null; currentThrowable = currentThrowable
+                .getCause()) {
+            if (currentThrowable instanceof IOException) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+
     /**
      * Adds a path to the java.library.path property, and flushes the path cache so
      * that subsequent System.load calls

SpecsUtils/src/pt/up/fe/specs/util/jobs/execution/ProcessExecution.java

@@ -16,6 +16,7 @@
 import java.io.File;
 import java.util.List;
 
+import pt.up.fe.specs.util.SpecsLogs;
 import pt.up.fe.specs.util.SpecsSystem;
 
 /**
@@ -45,7 +46,20 @@ public ProcessExecution(List<String> commandArgs, String workingFoldername) {
      */
     @Override
     public int run() {
-        return SpecsSystem.run(this.commandArgs, new File(this.workingFoldername));
+        try {
+            return SpecsSystem.run(this.commandArgs, new File(this.workingFoldername));
+        } catch (RuntimeException e) {
+            // Only a launch failure due to a missing command maps to a return
+            // code (the shell convention of 127, 'command not found'). Any
+            // other failure is not representable as an exit code and is
+            // rethrown, as the process may even have been running.
+            if (!SpecsSystem.isLaunchFailure(e)) {
+                throw e;
+            }
+
+            SpecsLogs.msgInfo("Could not run command '" + getCommandString() + "': " + e.getMessage());
+            return 127;
+        }
     }
 
     @Override