fixes elm/json#20

.gitignore

@@ -1 +1,4 @@
-elm-stuff
+elm-stuff/
+/artifacts.dat
+/docs.json
+/tests/.elm

.travis.yml

@@ -0,0 +1,11 @@
+language: elm
+
+elm:
+  - latest
+
+elm_test: latest
+
+elm_format: latest
+
+script:
+  - bash tests/run-tests.sh

tests/elm.json

@@ -0,0 +1,23 @@
+{
+    "type": "application",
+    "source-directories": [],
+    "elm-version": "0.19.1",
+    "dependencies": {
+        "direct": {
+            "elm/core": "1.0.4",
+            "elm/json": "1.1.3"
+        },
+        "indirect": {}
+    },
+    "test-dependencies": {
+        "direct": {
+            "elm-explorations/test": "1.2.2"
+        },
+        "indirect": {
+            "elm/html": "1.0.0",
+            "elm/random": "1.0.0",
+            "elm/time": "1.0.0",
+            "elm/virtual-dom": "1.0.2"
+        }
+    }
+}

tests/run-tests.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+
+set -o errexit;
+set -o nounset;
+
+#let the caller supply an ELM_TEST binary if desired
+if [ -z "${ELM_TEST:-}" ]; then
+    ELM_TEST=elm-test;
+fi
+
+# since elm/json is treated specially by the compiler (it's always
+# inserted as a dependency even when not declared explicitly), we use
+# a bit of a hack to make the tests run against the local source code
+# rather than the elm/json source fetched from package.elm-lang.org.
+
+# create a local directory where the compiler will look for the
+# elm/json source code:
+
+DIR="$(dirname $0)";
+
+cd "$DIR";
+
+export ELM_HOME="$(pwd)/.elm";
+
+rm -rf "$ELM_HOME" && mkdir -p "$ELM_HOME";
+
+# elm-test also puts some things in elm-stuff, start with a clean
+# slate there as well
+
+rm -rf elm-stuff;
+
+# now make an initial run of the tests to populate .elm and elm-stuff;
+# this will test against elm/json from package.elm-lang.org, so we
+# don't really care what the results are; we just need to force all
+# the *other* dependencies to be fetched and set up.
+
+echo "seeding framework for test dependencies ...";
+
+# '|| true' lets us ignore failures here and keep the script running.
+# useful when developing a fix for a bug that exists in the version of
+# elm/json hosted on package.elm-lang.org
+
+"${ELM_TEST}" tests/Test/Json.elm --fuzz=1 > /dev/null || true;
+
+# clear out the copy of elm/json fetched by the above and replace it
+# with the local source code we want to actually test
+
+VERSION_DIR="$(ls ${ELM_HOME}/0.19.1/packages/elm/json/)"
+CORE_PACKAGE_DIR="${ELM_HOME}/0.19.1/packages/elm/json/$VERSION_DIR"
+CORE_GIT_DIR="$(dirname $PWD)"
+
+echo;
+echo "Linking $CORE_PACKAGE_DIR to $CORE_GIT_DIR"
+echo;
+
+rm -rf "$CORE_PACKAGE_DIR"
+ln -sv "$CORE_GIT_DIR" "$CORE_PACKAGE_DIR"
+rm -vf "${CORE_GIT_DIR}"/*.dat "${CORE_GIT_DIR}"/doc*.json
+
+# we also need to clear out elm-test's elm-stuff dir, since otherwise
+# the compiler complains that its .dat files are out of sync
+
+rm -rf elm-stuff;
+
+# now we can run the tests against the symlinked source code for real
+
+echo;
+echo "running tests ...";
+echo;
+
+"${ELM_TEST}" tests/Test/Json.elm "$@";

tests/Json.elm → tests/tests/Test/Json.elm

@@ -49,8 +49,11 @@ intTests =
             , test "Decoder expects object finds array, was crashing runtime." <|
                 \() ->
                     Expect.equal
-                        (Err "Expecting an object but instead got: []")
-                        (Json.decodeString (Json.dict Json.float) "[]")
+                        (Err "Problem with the given value:\n\n[]\n\nExpecting an OBJECT")
+                        (Result.mapError
+                            Json.errorToString
+                            (Json.decodeString (Json.dict Json.float) "[]")
+                        )
             ]
 
 
@@ -71,7 +74,11 @@ customTests =
                 Ok _ ->
                     Expect.fail "expected `customDecoder` to produce a value of type Err, but got Ok"
 
-                Err message ->
+                Err error ->
+                    let
+                        message =
+                            Json.errorToString error
+                    in
                     if String.contains customErrorMessage message then
                         Expect.pass
                     else