Better Error Messages (#286)

* add new error messages to the parser, replacing almost all of the previous ones

* add tests for the new parse error messages

* simplify the node.go types and corresponding parser.go behavior

query/parser/build.sh

@@ -4,3 +4,4 @@
 DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
 
 peg -inline -switch $DIR/language.peg
+goimports -w $DIR/language.peg.go # format the file; optional

query/parser/error_test.go

@@ -0,0 +1,89 @@
+// Copyright 2015 - 2016 Square Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package parser
+
+import "testing"
+
+func TestErrorMessages(t *testing.T) {
+	type sample struct {
+		query   string
+		message string
+	}
+	tests := []sample{
+		{
+			query:   "select foo from",
+			message: "line 1, column 16: expected value to follow key 'from'",
+		},
+		{
+			query:   "select foo\nfrom -30m to now\nwhere app = 'mqe'",
+			message: `line 3, column 6: encountered "where" after property clause; "where" blocks must go BEFORE 'from' and 'to' specifiers`,
+		},
+		{
+			query:   "select foo\nfrom -30m to mow",
+			message: "line 2, column 13: expected value to follow key 'to'",
+		},
+		{
+			query:   "select foo + bar[blah='22']\nwhere tag != 'value' and qux = 'qux'\nfrom -30m to mow",
+			message: "line 3, column 13: expected value to follow key 'to'",
+		},
+		{
+			query:   "select foo + bar[\nwhere tag != 'value' and qux = 'qux'\nfrom -30m to mow",
+			message: `line 1, column 18: expected predicate to follow "[" after metric`,
+		},
+		{
+			query:   "select crazy#2dinvalid.metric + bar\nwhere tag != 'value' and qux = 'qux'\nfrom -30m to now",
+			message: `line 1, column 13: expected key (one of 'from', 'to', 'resolution', or 'sample by') or end of input but got "#2dinvalid.metric + bar\nwhere tag != 'value' and qux = 'qux'\nfrom -30m to now" following a completed expression`,
+		},
+		{
+			query:   "serlect foo from -30m to now",
+			message: `line 1, column 9: expected key (one of 'from', 'to', 'resolution', or 'sample by') or end of input but got "foo from -30m to now" following a completed expression`,
+		},
+		{
+			query:   "describe all where host = 'foo'",
+			message: `line 1, column 14: expected end of input after 'describe all' and optional match clause but got "where host = 'foo'"`,
+		},
+		{
+			query:   "select foo, bar,\nfrom -30m to now",
+			message: `line 1, column 17: expected expression to follow ","`,
+		},
+		{
+			query:   "select foo, bar[host = 'x' and]\nfrom -30m to now",
+			message: `line 1, column 31: expected predicate to follow "and" operator`,
+		},
+		{
+			query:   "select foo, bar[host = 'x' and '2']\nfrom -30m to now",
+			message: `line 1, column 31: expected predicate to follow "and" operator`,
+		},
+		{
+			query:   "select foo, bar[host = 'x'] {unclosed annotation\nfrom -30m to now",
+			message: `line 2, column 17: expected "}" to close "{" opened for annotation`,
+		},
+	}
+	for _, test := range tests {
+		_, err := Parse(test.query)
+		if err == nil {
+			t.Errorf("Expected error to happen in query\n\t%s\nbut not error happened", test.query)
+			continue
+		}
+		actual := err.Error()
+		if test.message == "" {
+			t.Errorf("In query\n\t%s\ngot out error message\n\t%s\n(no expected message was set)", test.query, actual)
+			continue
+		}
+		if test.message != actual {
+			t.Errorf("In query\n\t%s\ngot out error message\n\t%s\nbut expected\n\t%s", test.query, actual, test.message)
+		}
+	}
+}