Use strategic newlines to improve rule output readability

internal/result/result.go

@@ -21,6 +21,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"regexp"
 	"strings"
 	"text/template"
 
@@ -96,6 +97,8 @@ func (results *Type) Initialize() {
 	}
 }
 
+var blankLineRegexp = regexp.MustCompile("\n[[:space:]]*\n")
+
 // Record records the result of a rule and returns a text summary for it.
 func (results *Type) Record(lintedProject project.Type, ruleConfiguration ruleconfiguration.Type, ruleResult ruleresult.Type, ruleOutput string) string {
 	ruleLevel, err := rulelevel.RuleLevel(ruleConfiguration, ruleResult, lintedProject)
@@ -124,10 +127,13 @@ func (results *Type) Record(lintedProject project.Type, ruleConfiguration ruleco
 		table.SetColumnSeparator("")
 		table.SetNoWhiteSpace(true)
 		table.SetColWidth(width - len(prefix))
+		table.SetReflowDuringAutoWrap(false) // Reflow removes explicit line breaks.
 		table.Append([]string{prefix, message})
 		table.Render()
+		// Remove blank lines on explicit line breaks caused by tablewriter bug.
+		cleanedOutput := blankLineRegexp.ReplaceAllLiteralString(formattedOutput.String(), "\n")
 
-		return formattedOutput.String()
+		return cleanedOutput
 	}
 
 	if configuration.Verbose() {
@@ -138,7 +144,11 @@ func (results *Type) Record(lintedProject project.Type, ruleConfiguration ruleco
 		}
 	} else {
 		if ruleResult == ruleresult.Fail {
-			summaryText = formatRuleText(ruleLevel, fmt.Sprintf("%s (Rule %s)", ruleMessage, ruleConfiguration.ID))
+			if strings.Contains(ruleMessage, "\n") {
+				summaryText = formatRuleText(ruleLevel, fmt.Sprintf("%s\n(Rule %s)", ruleMessage, ruleConfiguration.ID))
+			} else {
+				summaryText = formatRuleText(ruleLevel, fmt.Sprintf("%s (Rule %s)", ruleMessage, ruleConfiguration.ID))
+			}
 		}
 	}
 

internal/result/result_test.go

@@ -85,9 +85,15 @@ func TestRecord(t *testing.T) {
 	assert.Equal(t, fmt.Sprintf("Rule %s result: %s\n", ruleConfiguration.ID, ruleresult.Pass), summaryText, "Non-failure result with no rule function output should only use preface")
 	flags.Set("verbose", "false")
 	require.Nil(t, configuration.Initialize(flags, projectPaths))
-	summaryText = results.Record(lintedProject, ruleConfiguration, ruleresult.Fail, ruleOutput)
-	outputAssertion = "ERROR: Path does not contain a valid Arduino library. See:                                                              \n       https://arduino.github.io/arduino-cli/latest/library-specification (Rule LS001)                                  \n"
-	assert.Equal(t, outputAssertion, summaryText)
+	ruleConfigurationCopy := ruleConfiguration
+	ruleConfigurationCopy.MessageTemplate = "bar"
+	summaryText = results.Record(lintedProject, ruleConfigurationCopy, ruleresult.Fail, ruleOutput)
+	outputAssertion = "ERROR: bar (Rule LS001)\n"
+	assert.Equal(t, outputAssertion, summaryText, "Rule ID is appended to non-verbose fail message on same line when rule message is single line")
+	ruleConfigurationCopy.MessageTemplate = "bar\nbaz"
+	summaryText = results.Record(lintedProject, ruleConfigurationCopy, ruleresult.Fail, ruleOutput)
+	outputAssertion = "ERROR: bar         \n       baz         \n       (Rule LS001)\n"
+	assert.Equal(t, outputAssertion, summaryText, "Rule ID is appended to non-verbose fail message on same line when rule message is multiple lines")
 	summaryText = results.Record(lintedProject, ruleConfiguration, ruleresult.NotRun, ruleOutput)
 	assert.Equal(t, "", summaryText, "Non-fail result should not result in output in non-verbose mode")
 	summaryText = results.Record(lintedProject, ruleConfiguration, ruleresult.Pass, "")