parse: allow default value expression starting with operators (#42)

Fixes #41
a8m · Feb 3, 2023 · 4932428 · 4932428
1 parent dffd717
commit 4932428
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Showing 3 changed files with 52 additions and 13 deletions.
diff --git a/parse/lex.go b/parse/lex.go
@@ -123,8 +123,8 @@ func (l *lexer) nextItem() item {
 // lex creates a new scanner for the input string.
 func lex(input string, noDigit bool) *lexer {
 	l := &lexer{
-		input: input,
-		items: make(chan item),
+		input:   input,
+		items:   make(chan item),
 		noDigit: noDigit,
 	}
 	go l.run()
@@ -172,7 +172,7 @@ Loop:
 				}
 				l.subsDepth++
 				l.emit(itemLeftDelim)
-				return lexSubstitution
+				return lexSubstitutionOperator
 			case isAlphaNumeric(r):
 				return lexVariable
 			}
@@ -204,24 +204,20 @@ func lexVariable(l *lexer) stateFn {
 	}
 	l.emit(itemVariable)
 	if l.subsDepth > 0 {
-		return lexSubstitution
+		return lexSubstitutionOperator
 	}
 	return lexText
 }
 
-// lexSubstitution scans the elements inside substitution delimiters.
-func lexSubstitution(l *lexer) stateFn {
+// lexSubstitutionOperator scans a starting substitution operator (if any) and continues with lexSubstitution
+func lexSubstitutionOperator(l *lexer) stateFn {
 	switch r := l.next(); {
 	case r == '}':
 		l.subsDepth--
 		l.emit(itemRightDelim)
 		return lexText
 	case r == eof || isEndOfLine(r):
 		return l.errorf("closing brace expected")
-	case isAlphaNumeric(r) && strings.HasPrefix(l.input[l.lastPos:], "${"):
-		fallthrough
-	case r == '$':
-		return lexVariable
 	case r == '+':
 		l.emit(itemPlus)
 	case r == '-':
@@ -236,9 +232,24 @@ func lexSubstitution(l *lexer) stateFn {
 			l.emit(itemColonEquals)
 		case '+':
 			l.emit(itemColonPlus)
-		default:
-			l.emit(itemText)
 		}
+	}
+	return lexSubstitution
+}
+
+// lexSubstitution scans the elements inside substitution delimiters.
+func lexSubstitution(l *lexer) stateFn {
+	switch r := l.next(); {
+	case r == '}':
+		l.subsDepth--
+		l.emit(itemRightDelim)
+		return lexText
+	case r == eof || isEndOfLine(r):
+		return l.errorf("closing brace expected")
+	case isAlphaNumeric(r) && strings.HasPrefix(l.input[l.lastPos:], "${"):
+		fallthrough
+	case r == '$':
+		return lexVariable
 	default:
 		l.emit(itemText)
 	}

diff --git a/parse/lex_test.go b/parse/lex_test.go
@@ -1,8 +1,8 @@
 package parse
 
 import (
-	"testing"
 	"strings"
+	"testing"
 )
 
 type lexTest struct {
@@ -76,6 +76,28 @@ var lexTests = []lexTest{
 		{itemText, 0, " foo"},
 		tEOF,
 	}},
+	{"substitution-leading-dash-1", "bar ${BAR:--1} foo", []item{
+		{itemText, 0, "bar "},
+		tLeft,
+		{itemVariable, 0, "BAR"},
+		tColDash,
+		{itemText, 0, "-"},
+		{itemText, 0, "1"},
+		tRight,
+		{itemText, 0, " foo"},
+		tEOF,
+	}},
+	{"substitution-leading-dash-2", "bar ${BAR:=-1} foo", []item{
+		{itemText, 0, "bar "},
+		tLeft,
+		{itemVariable, 0, "BAR"},
+		tColEquals,
+		{itemText, 0, "-"},
+		{itemText, 0, "1"},
+		tRight,
+		{itemText, 0, " foo"},
+		tEOF,
+	}},
 	{"closing brace error", "hello-${world", []item{
 		{itemText, 0, "hello-"},
 		tLeft,

diff --git a/parse/parse_test.go b/parse/parse_test.go
@@ -63,6 +63,12 @@ var parseTests = []parseTest{
 	{"issue #1", "${hello:=wo_rld} ${foo:=bar_baz}", "wo_rld bar_baz", errNone},
 	{"issue #2", "name: ${NAME:=foo_qux}, key: ${EMPTY:=baz_bar}", "name: foo_qux, key: baz_bar", errNone},
 	{"gh-issue-8", "prop=${HOME_URL-http://localhost:8080}", "prop=http://localhost:8080", errNone},
+	// operators as leading values
+	{"gh-issue-41-1", "${NOTSET--1}", "-1", errNone},
+	{"gh-issue-41-2", "${NOTSET:--1}", "-1", errNone},
+	{"gh-issue-41-3", "${NOTSET=-1}", "-1", errNone},
+	{"gh-issue-41-4", "${NOTSET:==1}", "=1", errNone},
+
 	// bad substitution
 	{"closing brace expected", "hello ${", "", errAll},