From a1353e77be48de80809109594c2435d890751c78 Mon Sep 17 00:00:00 2001
From: "M. Eric Irrgang" <ericirrgang@gmail.com>
Date: Fri, 12 Oct 2018 21:34:27 +0300
Subject: [PATCH] gmxapi::UsageError

Introduce gmxapi exception UsageError for invalid usage of gmxapi.

getMdrunnerSignal() now throws UsageError instead of asserting on
argument validity.

Change-Id: Ib010a998546ac96a83126ef941822b7e355d0784
---
 src/api/cpp/include/gmxapi/exceptions.h   | 13 +++++++++++++
 src/api/cpp/include/gmxapi/md/mdsignals.h |  1 +
 src/api/cpp/mdsignals.cpp                 |  6 ++++--
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/api/cpp/include/gmxapi/exceptions.h b/src/api/cpp/include/gmxapi/exceptions.h
index 280c39e643..34272a825c 100644
--- a/src/api/cpp/include/gmxapi/exceptions.h
+++ b/src/api/cpp/include/gmxapi/exceptions.h
@@ -172,6 +172,19 @@ class NotImplementedError : public BasicException<NotImplementedError>
         using BasicException<NotImplementedError>::BasicException;
 };
 
+/*!
+ * \brief Unacceptable API usage.
+ *
+ * Usage error. Examples include calling a function with invalid arguments.
+ *
+ * \ingroup gmxapi_exceptions
+ */
+class UsageError : public BasicException<UsageError>
+{
+    public:
+        using BasicException<UsageError>::BasicException;
+};
+
 }      // end namespace gmxapi
 
 #endif // header guard
diff --git a/src/api/cpp/include/gmxapi/md/mdsignals.h b/src/api/cpp/include/gmxapi/md/mdsignals.h
index 17a6ac13c1..28abd58d7e 100644
--- a/src/api/cpp/include/gmxapi/md/mdsignals.h
+++ b/src/api/cpp/include/gmxapi/md/mdsignals.h
@@ -131,6 +131,7 @@ class Signal
  * \return Callable function object handle to issue a stop signal.
  *
  * \throws gmxapi::NotImplementedError for unknown values of signal.
+ * \throws gmxapi::UsageError for invalid resources argument.
  *
  * \ingroup gmxapi_md
  */
diff --git a/src/api/cpp/mdsignals.cpp b/src/api/cpp/mdsignals.cpp
index 910838c1a6..da00f81e6e 100644
--- a/src/api/cpp/mdsignals.cpp
+++ b/src/api/cpp/mdsignals.cpp
@@ -178,8 +178,10 @@ Signal getMdrunnerSignal(SessionResources *resources,
         throw gmxapi::NotImplementedError("This signaller only handles stop signals.");
     }
 
-    // TODO: replace with an exception.
-    GMX_RELEASE_ASSERT(resources, "Caller must provide a valid SessionResources to getMdrunnerSignal.");
+    if (resources == nullptr)
+    {
+        throw gmxapi::UsageError("Caller must provide a valid SessionResources to getMdrunnerSignal.");
+    }
 
     auto signaller = resources->getMdrunnerSignal(signal);
 
-- 
2.11.4.GIT