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|
package spec
import (
"strings"
"testing"
)
func TestParse(t *testing.T) {
production := func(lhs string, alts ...*AlternativeNode) *ProductionNode {
return &ProductionNode{
LHS: lhs,
RHS: alts,
}
}
alternative := func(elems ...*ElementNode) *AlternativeNode {
return &AlternativeNode{
Elements: elems,
}
}
id := func(id string) *ElementNode {
return &ElementNode{
ID: id,
}
}
pattern := func(p string) *ElementNode {
return &ElementNode{
Pattern: p,
}
}
tests := []struct {
caption string
src string
ast *RootNode
synErr *SyntaxError
}{
{
caption: "single production is a valid grammar",
src: `a: "a";`,
ast: &RootNode{
Productions: []*ProductionNode{
production("a", alternative(pattern("a"))),
},
},
},
{
caption: "multiple productions are a valid grammar",
src: `
e: e "\+|-" t | t;
t: t "\*|/" f | f;
f: "\(" e ")" | id;
id: "[A-Za-z_][0-9A-Za-z_]*";
`,
ast: &RootNode{
Productions: []*ProductionNode{
production("e",
alternative(id("e"), pattern(`\+|-`), id("t")),
alternative(id("t")),
),
production("t",
alternative(id("t"), pattern(`\*|/`), id("f")),
alternative(id("f")),
),
production("f",
alternative(pattern(`\(`), id("e"), pattern(`)`)),
alternative(id("id")),
),
production("id",
alternative(pattern(`[A-Za-z_][0-9A-Za-z_]*`)),
),
},
},
},
{
caption: "productions can contain the empty alternative",
src: `
a: "foo" | ;
b: | "bar";
c: ;
`,
ast: &RootNode{
Productions: []*ProductionNode{
production("a",
alternative(pattern(`foo`)),
alternative(),
),
production("b",
alternative(),
alternative(pattern(`bar`)),
),
production("c",
alternative(),
),
},
},
},
{
caption: "when a source contains an unknown token, the parser raises a syntax error",
src: `a: !;`,
synErr: synErrInvalidToken,
},
{
caption: "a grammar must have at least one production",
src: ``,
synErr: synErrNoProduction,
},
{
caption: "a production must have its name as the first element",
src: `: "a";`,
synErr: synErrNoProductionName,
},
{
caption: "':' must precede an alternative",
src: `a "a";`,
synErr: synErrNoColon,
},
{
caption: "';' must follow a production",
src: `a: "a"`,
synErr: synErrNoSemicolon,
},
{
caption: "';' can only appear at the end of a production",
src: `;`,
synErr: synErrNoProductionName,
},
}
for _, tt := range tests {
t.Run(tt.caption, func(t *testing.T) {
ast, err := Parse(strings.NewReader(tt.src))
if tt.synErr != nil {
if tt.synErr != err {
t.Fatalf("unexpected error; want: %v, got: %v", tt.synErr, err)
}
if ast != nil {
t.Fatalf("AST must be nil")
}
} else {
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
if ast == nil {
t.Fatalf("AST must be non-nil")
}
testRootNode(t, ast, tt.ast)
}
})
}
}
func testRootNode(t *testing.T, root, expected *RootNode) {
t.Helper()
if len(root.Productions) != len(expected.Productions) {
t.Fatalf("unexpected length of productions; want: %v, got: %v", len(expected.Productions), len(root.Productions))
}
for i, prod := range root.Productions {
testProductionNode(t, prod, expected.Productions[i])
}
}
func testProductionNode(t *testing.T, prod, expected *ProductionNode) {
t.Helper()
if prod.LHS != expected.LHS {
t.Fatalf("unexpected LHS; want: %v, got: %v", expected.LHS, prod.LHS)
}
if len(prod.RHS) != len(expected.RHS) {
t.Fatalf("unexpected length of an RHS; want: %v, got: %v", len(expected.RHS), len(prod.RHS))
}
for i, alt := range prod.RHS {
testAlternativeNode(t, alt, expected.RHS[i])
}
}
func testAlternativeNode(t *testing.T, alt, expected *AlternativeNode) {
t.Helper()
if len(alt.Elements) != len(expected.Elements) {
t.Fatalf("unexpected length of elements; want: %v, got: %v", len(expected.Elements), len(alt.Elements))
}
for i, elem := range alt.Elements {
testElementNode(t, elem, expected.Elements[i])
}
}
func testElementNode(t *testing.T, elem, expected *ElementNode) {
t.Helper()
if elem.Pattern != expected.Pattern {
t.Fatalf("unexpected pattern; want: %v, got: %v", expected.Pattern, elem.Pattern)
}
}
|
