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|
package grammar
import (
"strings"
"testing"
"github.com/nihei9/vartan/spec"
)
type follow struct {
nonTermText string
symbols []string
eof bool
}
func TestFollowSet(t *testing.T) {
tests := []struct {
caption string
src string
follow []follow
}{
{
caption: "productions contain only non-empty productions",
src: `
expr
: expr add term
| term
;
term
: term mul factor
| factor
;
factor
: l_paren expr r_paren
| id
;
add: "\+";
mul: "\*";
l_paren: "\(";
r_paren: "\)";
id: "[A-Za-z_][0-9A-Za-z_]*";
`,
follow: []follow{
{nonTermText: "expr'", symbols: []string{}, eof: true},
{nonTermText: "expr", symbols: []string{"add", "r_paren"}, eof: true},
{nonTermText: "term", symbols: []string{"add", "mul", "r_paren"}, eof: true},
{nonTermText: "factor", symbols: []string{"add", "mul", "r_paren"}, eof: true},
},
},
{
caption: "productions contain an empty start production",
src: `
s
:
;
`,
follow: []follow{
{nonTermText: "s'", symbols: []string{}, eof: true},
{nonTermText: "s", symbols: []string{}, eof: true},
},
},
{
caption: "productions contain an empty production",
src: `
s
: foo
;
foo
:
;
`,
follow: []follow{
{nonTermText: "s'", symbols: []string{}, eof: true},
{nonTermText: "s", symbols: []string{}, eof: true},
{nonTermText: "foo", symbols: []string{}, eof: true},
},
},
{
caption: "a start production contains a non-empty alternative and empty alternative",
src: `
s
: foo
|
;
foo: "foo";
`,
follow: []follow{
{nonTermText: "s'", symbols: []string{}, eof: true},
{nonTermText: "s", symbols: []string{}, eof: true},
},
},
{
caption: "a production contains non-empty alternative and empty alternative",
src: `
s
: foo
;
foo
: bar
|
;
bar: "bar";
`,
follow: []follow{
{nonTermText: "s'", symbols: []string{}, eof: true},
{nonTermText: "s", symbols: []string{}, eof: true},
{nonTermText: "foo", symbols: []string{}, eof: true},
},
},
}
for _, tt := range tests {
t.Run(tt.caption, func(t *testing.T) {
flw, gram := genActualFollow(t, tt.src)
for _, ttFollow := range tt.follow {
sym, ok := gram.symbolTable.toSymbol(ttFollow.nonTermText)
if !ok {
t.Fatalf("a symbol '%v' was not found", ttFollow.nonTermText)
}
actualFollow, err := flw.find(sym)
if err != nil {
t.Fatalf("failed to get a FOLLOW entry; non-terminal symbol: %v (%v), error: %v", ttFollow.nonTermText, sym, err)
}
expectedFollow := genExpectedFollowEntry(t, ttFollow.symbols, ttFollow.eof, gram.symbolTable)
testFollow(t, actualFollow, expectedFollow)
}
})
}
}
func genActualFollow(t *testing.T, src string) (*followSet, *Grammar) {
ast, err := spec.Parse(strings.NewReader(src))
if err != nil {
t.Fatal(err)
}
b := GrammarBuilder{
AST: ast,
}
gram, err := b.Build()
if err != nil {
t.Fatal(err)
}
fst, err := genFirstSet(gram.productionSet)
if err != nil {
t.Fatal(err)
}
flw, err := genFollowSet(gram.productionSet, fst)
if flw == nil {
t.Fatal("genFollow returned nil without any error")
}
return flw, gram
}
func genExpectedFollowEntry(t *testing.T, symbols []string, eof bool, symTab *symbolTable) *followEntry {
t.Helper()
entry := newFollowEntry()
if eof {
entry.addEOF()
}
for _, sym := range symbols {
symID, _ := symTab.toSymbol(sym)
if symID.isNil() {
t.Fatalf("a symbol '%v' was not found", sym)
}
entry.add(symID)
}
return entry
}
func testFollow(t *testing.T, actual, expected *followEntry) {
if actual.eof != expected.eof {
t.Errorf("eof is mismatched; want: %v, got: %v", expected.eof, actual.eof)
}
if len(actual.symbols) != len(expected.symbols) {
t.Fatalf("unexpected symbol count of a FOLLOW entry; want: %v, got: %v", expected.symbols, actual.symbols)
}
for eSym := range expected.symbols {
if _, ok := actual.symbols[eSym]; !ok {
t.Fatalf("invalid FOLLOW entry; want: %v, got: %v", expected.symbols, actual.symbols)
}
}
}
|
