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syntax: handle UnaryExpr{Op:STAR, X:nil} (google#158)
In "def f(*, x)", the unary expression has no operand. Document this and be appropriately defensive. Add another test (and example) of walk. Also: - visit Comprehension.Body before Clauses and fix existing TestWalk. - move existing TestWalk Fixes google#157
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,103 @@ | ||
| package syntax_test | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "fmt" | ||
| "log" | ||
| "reflect" | ||
| "strings" | ||
| "testing" | ||
|
|
||
| "go.starlark.net/syntax" | ||
| ) | ||
|
|
||
| func TestWalk(t *testing.T) { | ||
| const src = ` | ||
| for x in y: | ||
| if x: | ||
| pass | ||
| else: | ||
| f([2*x for x in "abc"]) | ||
| ` | ||
| // TODO(adonovan): test that it finds all syntax.Nodes | ||
| // (compare against a reflect-based implementation). | ||
| // TODO(adonovan): test that the result of f is used to prune | ||
| // the descent. | ||
| f, err := syntax.Parse("hello.go", src, 0) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
|
|
||
| var buf bytes.Buffer | ||
| var depth int | ||
| syntax.Walk(f, func(n syntax.Node) bool { | ||
| if n == nil { | ||
| depth-- | ||
| return true | ||
| } | ||
| fmt.Fprintf(&buf, "%s%s\n", | ||
| strings.Repeat(" ", depth), | ||
| strings.TrimPrefix(reflect.TypeOf(n).String(), "*syntax.")) | ||
| depth++ | ||
| return true | ||
| }) | ||
| got := buf.String() | ||
| want := ` | ||
| File | ||
| ForStmt | ||
| Ident | ||
| Ident | ||
| IfStmt | ||
| Ident | ||
| BranchStmt | ||
| ExprStmt | ||
| CallExpr | ||
| Ident | ||
| Comprehension | ||
| BinaryExpr | ||
| Literal | ||
| Ident | ||
| ForClause | ||
| Ident | ||
| Literal` | ||
| got = strings.TrimSpace(got) | ||
| want = strings.TrimSpace(want) | ||
| if got != want { | ||
| t.Errorf("got %s, want %s", got, want) | ||
| } | ||
| } | ||
|
|
||
| // ExampleWalk demonstrates the use of Walk to | ||
| // enumerate the identifiers in a Starlark source file | ||
| // containing a nonsense program with varied grammar. | ||
| func ExampleWalk() { | ||
| const src = ` | ||
| load("library", "a") | ||
| def b(c, *, d=e): | ||
| f += {g: h} | ||
| i = -(j) | ||
| return k.l[m + n] | ||
| for o in [p for q, r in s if t]: | ||
| u(lambda: v, w[x:y:z]) | ||
| ` | ||
| f, err := syntax.Parse("hello.star", src, 0) | ||
| if err != nil { | ||
| log.Fatal(err) | ||
| } | ||
|
|
||
| var idents []string | ||
| syntax.Walk(f, func(n syntax.Node) bool { | ||
| if id, ok := n.(*syntax.Ident); ok { | ||
| idents = append(idents, id.Name) | ||
| } | ||
| return true | ||
| }) | ||
| fmt.Println(strings.Join(idents, " ")) | ||
|
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||
| // The identifer 'a' appears in both LoadStmt.From[0] and LoadStmt.To[0]. | ||
|
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||
| // Output: | ||
| // a a b c d e f g h i j k l m n o p q r s t u v w x y z | ||
| } |