Improved module errors

lib/modules.nix

@@ -117,7 +117,7 @@ rec {
         if config._module.check && config._module.freeformType == null && merged.unmatchedDefns != [] then
           let
             firstDef = head merged.unmatchedDefns;
-            baseMsg = "The option `${showOption (prefix ++ firstDef.prefix)}' defined in `${firstDef.file}' does not exist.";
+            baseMsg = "The option `${showOption (prefix ++ firstDef.prefix)}' does not exist. Definition values:${showDefs [ firstDef ]}";
           in
             if attrNames options == [ "_module" ]
               then throw ''
@@ -449,7 +449,13 @@ rec {
       # Handle properties, check types, and merge everything together.
       res =
         if opt.readOnly or false && length defs' > 1 then
-          throw "The option `${showOption loc}' is read-only, but it's set multiple times."
+          let
+            # For a better error message, evaluate all readOnly definitions as
+            # if they were the only definition.
+            separateDefs = map (def: def // {
+              value = (mergeDefinitions loc opt.type [ def ]).mergedValue;
+            }) defs';
+          in throw "The option `${showOption loc}' is read-only, but it's set multiple times. Definition values:${showDefs separateDefs}"
         else
           mergeDefinitions loc opt.type defs';
 
@@ -497,8 +503,8 @@ rec {
     mergedValue =
       if isDefined then
         if all (def: type.check def.value) defsFinal then type.merge loc defsFinal
-        else let firstInvalid = findFirst (def: ! type.check def.value) null defsFinal;
-        in throw "The option value `${showOption loc}' in `${firstInvalid.file}' is not of type `${type.description}'."
+        else let allInvalid = filter (def: ! type.check def.value) defsFinal;
+        in throw "A definition for option `${showOption loc}' is not of type `${type.description}'. Definition values:${showDefs allInvalid}"
       else
         # (nixos-option detects this specific error message and gives it special
         # handling.  If changed here, please change it there too.)

lib/options.nix

@@ -96,12 +96,12 @@ rec {
     else if all isBool list then foldl' lib.or false list
     else if all isString list then lib.concatStrings list
     else if all isInt list && all (x: x == head list) list then head list
-    else throw "Cannot merge definitions of `${showOption loc}' given in ${showFiles (getFiles defs)}.";
+    else throw "Cannot merge definitions of `${showOption loc}'. Definition values:${showDefs defs}";
 
   mergeOneOption = loc: defs:
     if defs == [] then abort "This case should never happen."
     else if length defs != 1 then
-      throw "The unique option `${showOption loc}' is defined multiple times, in:\n - ${concatStringsSep "\n - " (getFiles defs)}."
+      throw "The unique option `${showOption loc}' is defined multiple times. Definition values:${showDefs defs}"
     else (head defs).value;
 
   /* "Merge" option definitions by checking that they all have the same value. */
@@ -111,11 +111,11 @@ rec {
     # This also makes it work for functions, because the foldl' below would try
     # to compare the first element with itself, which is false for functions
     else if length defs == 1 then (elemAt defs 0).value
-    else foldl' (val: def:
-      if def.value != val then
-        throw "The option `${showOption loc}' has conflicting definitions, in ${showFiles (getFiles defs)}."
+    else (foldl' (first: def:
+      if def.value != first.value then
+        throw "The option `${showOption loc}' has conflicting definition values:${showDefs [ first def ]}"
       else
-        val) (head defs).value defs;
+        first) (head defs) defs).value;
 
   /* Extracts values of all "value" keys of the given list.
 
@@ -213,6 +213,24 @@ rec {
          else escaped;
     in (concatStringsSep ".") (map escapeOptionPart parts);
   showFiles = files: concatStringsSep " and " (map (f: "`${f}'") files);
+
+  showDefs = defs: concatMapStrings (def:
+    let
+      # Pretty print the value for display, if successful
+      prettyEval = builtins.tryEval (lib.generators.toPretty {} def.value);
+      # Split it into its lines
+      lines = filter (v: ! isList v) (builtins.split "\n" prettyEval.value);
+      # Only display the first 5 lines, and indent them for better visibility
+      value = concatStringsSep "\n    " (take 5 lines ++ optional (length lines > 5) "...");
+      result =
+        # Don't print any value if evaluating the value strictly fails
+        if ! prettyEval.success then ""
+        # Put it on a new line if it consists of multiple
+        else if length lines > 1 then ":\n    " + value
+        else ": " + value;
+    in "\n- In `${def.file}'${result}"
+  ) defs;
+
   unknownModule = "<unknown-file>";
 
 }

lib/tests/modules.sh

@@ -49,7 +49,7 @@ checkConfigError() {
         reportFailure "$@"
         return 1
     else
-        if echo "$err" | grep --silent "$errorContains" ; then
+        if echo "$err" | grep -zP --silent "$errorContains" ; then
             pass=$((pass + 1))
             return 0;
         else
@@ -62,17 +62,17 @@ checkConfigError() {
 
 # Check boolean option.
 checkConfigOutput "false" config.enable ./declare-enable.nix
-checkConfigError 'The option .* defined in .* does not exist.' config.enable ./define-enable.nix
+checkConfigError 'The option .* does not exist. Definition values:\n- In .*: true' config.enable ./define-enable.nix
 
 # Check integer types.
 # unsigned
 checkConfigOutput "42" config.value ./declare-int-unsigned-value.nix ./define-value-int-positive.nix
-checkConfigError 'The option value .* in .* is not of type.*unsigned integer.*' config.value ./declare-int-unsigned-value.nix ./define-value-int-negative.nix
+checkConfigError 'A definition for option .* is not of type.*unsigned integer.*. Definition values:\n- In .*: -23' config.value ./declare-int-unsigned-value.nix ./define-value-int-negative.nix
 # positive
-checkConfigError 'The option value .* in .* is not of type.*positive integer.*' config.value ./declare-int-positive-value.nix ./define-value-int-zero.nix
+checkConfigError 'A definition for option .* is not of type.*positive integer.*. Definition values:\n- In .*: 0' config.value ./declare-int-positive-value.nix ./define-value-int-zero.nix
 # between
 checkConfigOutput "42" config.value ./declare-int-between-value.nix ./define-value-int-positive.nix
-checkConfigError 'The option value .* in .* is not of type.*between.*-21 and 43.*inclusive.*' config.value ./declare-int-between-value.nix ./define-value-int-negative.nix
+checkConfigError 'A definition for option .* is not of type.*between.*-21 and 43.*inclusive.*. Definition values:\n- In .*: -23' config.value ./declare-int-between-value.nix ./define-value-int-negative.nix
 
 # Check either types
 # types.either
@@ -125,7 +125,7 @@ checkConfigOutput 'true' "$@" ./define-enable.nix ./define-attrsOfSub-foo-enable
 set -- config.enable ./define-enable.nix ./declare-enable.nix
 checkConfigOutput "true" "$@"
 checkConfigOutput "false" "$@" ./disable-define-enable.nix
-checkConfigError "The option .*enable.* defined in .* does not exist" "$@" ./disable-declare-enable.nix
+checkConfigError "The option .*enable.* does not exist. Definition values:\n- In .*: true" "$@" ./disable-declare-enable.nix
 checkConfigError "attribute .*enable.* in selection path .*config.enable.* not found" "$@" ./disable-define-enable.nix ./disable-declare-enable.nix
 checkConfigError "attribute .*enable.* in selection path .*config.enable.* not found" "$@" ./disable-enable-modules.nix
 
@@ -142,17 +142,17 @@ checkConfigError 'infinite recursion encountered' "$@"
 
 # Check _module.check.
 set -- config.enable ./declare-enable.nix ./define-enable.nix ./define-attrsOfSub-foo.nix
-checkConfigError 'The option .* defined in .* does not exist.' "$@"
+checkConfigError 'The option .* does not exist. Definition values:\n- In .*' "$@"
 checkConfigOutput "true" "$@" ./define-module-check.nix
 
 # Check coerced value.
 checkConfigOutput "\"42\"" config.value ./declare-coerced-value.nix
 checkConfigOutput "\"24\"" config.value ./declare-coerced-value.nix ./define-value-string.nix
-checkConfigError 'The option value .* in .* is not.*string or signed integer convertible to it' config.value ./declare-coerced-value.nix ./define-value-list.nix
+checkConfigError 'A definition for option .* is not.*string or signed integer convertible to it.*. Definition values:\n- In .*: \[ \]' config.value ./declare-coerced-value.nix ./define-value-list.nix
 
 # Check coerced value with unsound coercion
 checkConfigOutput "12" config.value ./declare-coerced-value-unsound.nix
-checkConfigError 'The option value .* in .* is not.*8 bit signed integer.* or string convertible to it' config.value ./declare-coerced-value-unsound.nix ./define-value-string-bigint.nix
+checkConfigError 'A definition for option .* is not of type .*. Definition values:\n- In .*: "1000"' config.value ./declare-coerced-value-unsound.nix ./define-value-string-bigint.nix
 checkConfigError 'unrecognised JSON value' config.value ./declare-coerced-value-unsound.nix ./define-value-string-arbitrary.nix
 
 # Check mkAliasOptionModule.
@@ -183,7 +183,7 @@ checkConfigOutput "true" config.submodule.enable ./declare-submoduleWith-path.ni
 checkConfigOutput "true" config.enable ./disable-recursive/main.nix
 checkConfigOutput "true" config.enable ./disable-recursive/{main.nix,disable-foo.nix}
 checkConfigOutput "true" config.enable ./disable-recursive/{main.nix,disable-bar.nix}
-checkConfigError 'The option .* defined in .* does not exist' config.enable ./disable-recursive/{main.nix,disable-foo.nix,disable-bar.nix}
+checkConfigError 'The option .* does not exist. Definition values:\n- In .*: true' config.enable ./disable-recursive/{main.nix,disable-foo.nix,disable-bar.nix}
 
 # Check that imports can depend on derivations
 checkConfigOutput "true" config.enable ./import-from-store.nix
@@ -207,7 +207,7 @@ checkConfigOutput "empty" config.value.foo ./declare-lazyAttrsOf.nix ./attrsOf-c
 
 
 # Even with multiple assignments, a type error should be thrown if any of them aren't valid
-checkConfigError 'The option value .* in .* is not of type .*' \
+checkConfigError 'A definition for option .* is not of type .*' \
   config.value ./declare-int-unsigned-value.nix ./define-value-list.nix ./define-value-int-positive.nix
 
 ## Freeform modules
@@ -216,7 +216,7 @@ checkConfigOutput 24 config.value ./freeform-attrsOf.nix ./define-value-string.n
 # No freeform assigments shouldn't make it error
 checkConfigOutput '{ }' config ./freeform-attrsOf.nix
 # but only if the type matches
-checkConfigError 'The option value .* in .* is not of type .*' config.value ./freeform-attrsOf.nix ./define-value-list.nix
+checkConfigError 'A definition for option .* is not of type .*' config.value ./freeform-attrsOf.nix ./define-value-list.nix
 # and properties should be applied
 checkConfigOutput yes config.value ./freeform-attrsOf.nix ./define-value-string-properties.nix
 # Options should still be declarable, and be able to have a type that doesn't match the freeform type
@@ -251,7 +251,7 @@ checkConfigOutput / config.value.path ./types-anything/equal-atoms.nix
 checkConfigOutput null config.value.null ./types-anything/equal-atoms.nix
 checkConfigOutput 0.1 config.value.float ./types-anything/equal-atoms.nix
 # Functions can't be merged together
-checkConfigError "The option .* has conflicting definitions" config.value.multiple-lambdas ./types-anything/functions.nix
+checkConfigError "The option .* has conflicting definition values" config.value.multiple-lambdas ./types-anything/functions.nix
 checkConfigOutput '<LAMBDA>' config.value.single-lambda ./types-anything/functions.nix
 # Check that all mk* modifiers are applied
 checkConfigError 'attribute .* not found' config.value.mkiffalse ./types-anything/mk-mods.nix

lib/types.nix

@@ -299,16 +299,14 @@ rec {
       check = isList;
       merge = loc: defs:
         map (x: x.value) (filter (x: x ? value) (concatLists (imap1 (n: def:
-          if isList def.value then
-            imap1 (m: def':
-              (mergeDefinitions
-                (loc ++ ["[definition ${toString n}-entry ${toString m}]"])
-                elemType
-                [{ inherit (def) file; value = def'; }]
-              ).optionalValue
-            ) def.value
-          else
-            throw "The option value `${showOption loc}` in `${def.file}` is not a list.") defs)));
+          imap1 (m: def':
+            (mergeDefinitions
+              (loc ++ ["[definition ${toString n}-entry ${toString m}]"])
+              elemType
+              [{ inherit (def) file; value = def'; }]
+            ).optionalValue
+          ) def.value
+        ) defs)));
       emptyValue = { value = {}; };
       getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["*"]);
       getSubModules = elemType.getSubModules;