4 files changed, 54 insertions, 4 deletions

diff --git a/src/libcmd/installable-flake.cc b/src/libcmd/installable-flake.cc
index 615f70945..46bdd411b 100644
--- a/src/libcmd/installable-flake.cc
+++ b/src/libcmd/installable-flake.cc
@@ -105,9 +105,14 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
             fmt("while evaluating the flake output attribute '%s'", attrPath)))
         {
             return { *derivedPathWithInfo };
+        } else {
+            throw Error(
+                "expected flake output attribute '%s' to be a derivation or path but found %s: %s",
+                attrPath,
+                showType(v),
+                ValuePrinter(*this->state, v, errorPrintOptions)
+            );
         }
-        else
-            throw Error("flake output attribute '%s' is not a derivation or path", attrPath);
     }
 
     auto drvPath = attr->forceDerivation();
diff --git a/src/libcmd/repl-interacter.cc b/src/libcmd/repl-interacter.cc
index 829383add..41589cda1 100644
--- a/src/libcmd/repl-interacter.cc
+++ b/src/libcmd/repl-interacter.cc
@@ -1,6 +1,8 @@
 #include <cstdio>
 #include <iostream>
 #include <string>
+#include <string_view>
+#include <cerrno>
 
 #ifdef READLINE
 #include <readline/history.h>
@@ -175,14 +177,43 @@ bool ReadlineLikeInteracter::getLine(std::string & input, ReplPromptType promptT
 
     if (!s)
         return false;
+
+    this->writeHistory();
     input += s;
     input += '\n';
     return true;
 }
 
+void ReadlineLikeInteracter::writeHistory()
+{
+    int ret = write_history(historyFile.c_str());
+    int writeHistErr = errno;
+
+    if (ret == 0) {
+        return;
+    }
+
+    // If the open fails, editline returns EOF. If the close fails, editline
+    // forwards the return value of fclose(), which is EOF on error.
+    // readline however, returns the errno.
+    // So if we didn't get exactly EOF, then consider the return value the error
+    // code; otherwise use the errno we saved above.
+    // https://github.com/troglobit/editline/issues/66
+    if (ret != EOF) {
+        writeHistErr = ret;
+    }
+
+    // In any of these cases, we should explicitly ignore the error, but log
+    // them so the user isn't confused why their history is getting eaten.
+
+    std::string_view const errMsg(std::strerror(writeHistErr));
+    warn("ignoring error writing repl history to %s: %s", this->historyFile, errMsg);
+
+}
+
 ReadlineLikeInteracter::~ReadlineLikeInteracter()
 {
-    write_history(historyFile.c_str());
+    this->writeHistory();
 }
 
 AutomationInteracter::Guard AutomationInteracter::init(detail::ReplCompleterMixin *)
diff --git a/src/libcmd/repl-interacter.hh b/src/libcmd/repl-interacter.hh
index c31b1a1e6..8f815fceb 100644
--- a/src/libcmd/repl-interacter.hh
+++ b/src/libcmd/repl-interacter.hh
@@ -42,6 +42,11 @@ public:
     }
     virtual Guard init(detail::ReplCompleterMixin * repl) override;
     virtual bool getLine(std::string & input, ReplPromptType promptType) override;
+    /** Writes the current history to the history file.
+     *
+     * This function logs but ignores errors from readline's write_history().
+     */
+    virtual void writeHistory();
     virtual ~ReadlineLikeInteracter() override;
 };
 
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 525c25560..46b6d57ed 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -90,7 +90,8 @@ struct NixRepl
     Strings loadedFiles;
     std::function<AnnotatedValues()> getValues;
 
-    const static int envSize = 32768;
+    // Uses 8MiB of memory. It's fine.
+    const static int envSize = 1 << 20;
     std::shared_ptr<StaticEnv> staticEnv;
     Env * env;
     int displ;
@@ -375,6 +376,9 @@ StringSet NixRepl::completePrefix(const std::string & prefix)
             // Quietly ignore evaluation errors.
         } catch (BadURL & e) {
             // Quietly ignore BadURL flake-related errors.
+        } catch (SysError & e) {
+            // Quietly ignore system errors which can for example be raised by
+            // a non-existent file being `import`-ed.
         }
     }
 
@@ -854,6 +858,11 @@ void NixRepl::loadReplOverlays()
         replInitFilesFunction->determinePos(noPos)
     );
 
+    // n.b. this does in fact load the stuff into the environment twice (once
+    // from the superset of the environment returned by repl-overlays and once
+    // from the thing itself), but it's not fixable because clearEnv here could
+    // lead to dangling references to the old environment in thunks.
+    // https://git.lix.systems/lix-project/lix/issues/337#issuecomment-3745
     addAttrsToScope(newAttrs);
 }