internal: hoist attribute parsing logic
Change-Id: I76b2163dc717aba19a51b9daa0544792c7a8d599
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/4900
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/internal/attrs.go b/internal/attrs.go
new file mode 100644
index 0000000..c0d03c8
--- /dev/null
+++ b/internal/attrs.go
@@ -0,0 +1,205 @@
+// Copyright 2020 CUE Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+ "fmt"
+ "strconv"
+ "strings"
+
+ "cuelang.org/go/cue/errors"
+ "cuelang.org/go/cue/literal"
+ "cuelang.org/go/cue/token"
+)
+
+// Attr holds positional information for a single Attr.
+type Attr struct {
+ Fields []keyValue
+ Err error
+}
+
+// NewNonExisting creates a non-existing attribute.
+func NewNonExisting(key string) Attr {
+ const msgNotExist = "attribute %q does not exist"
+ return Attr{Err: errors.Newf(token.NoPos, msgNotExist, key)}
+}
+
+type keyValue struct {
+ data string
+ equal int // index of equal sign or 0 if non-existing
+}
+
+func (kv *keyValue) Text() string { return kv.data }
+func (kv *keyValue) Key() string { return kv.data[:kv.equal] }
+func (kv *keyValue) Value() string {
+ return strings.TrimSpace(kv.data[kv.equal+1:])
+}
+
+func (a *Attr) hasPos(p int) error {
+ if a.Err != nil {
+ return a.Err
+ }
+ if p >= len(a.Fields) {
+ return fmt.Errorf("field does not exist")
+ }
+ return nil
+}
+
+// String reports the possibly empty string value at the given position or
+// an error the attribute is invalid or if the position does not exist.
+func (a *Attr) String(pos int) (string, error) {
+ if err := a.hasPos(pos); err != nil {
+ return "", err
+ }
+ return a.Fields[pos].Text(), nil
+}
+
+// Int reports the integer at the given position or an error if the attribute is
+// invalid, the position does not exist, or the value at the given position is
+// not an integer.
+func (a *Attr) Int(pos int) (int64, error) {
+ if err := a.hasPos(pos); err != nil {
+ return 0, err
+ }
+ // TODO: use CUE's literal parser once it exists, allowing any of CUE's
+ // number types.
+ return strconv.ParseInt(a.Fields[pos].Text(), 10, 64)
+}
+
+// Flag reports whether an entry with the given name exists at position pos or
+// onwards or an error if the attribute is invalid or if the first pos-1 entries
+// are not defined.
+func (a *Attr) Flag(pos int, key string) (bool, error) {
+ if err := a.hasPos(pos - 1); err != nil {
+ return false, err
+ }
+ for _, kv := range a.Fields[pos:] {
+ if kv.Text() == key {
+ return true, nil
+ }
+ }
+ return false, nil
+}
+
+// Lookup searches for an entry of the form key=value from position pos onwards
+// and reports the value if found. It reports an error if the attribute is
+// invalid or if the first pos-1 entries are not defined.
+func (a *Attr) Lookup(pos int, key string) (val string, found bool, err error) {
+ if err := a.hasPos(pos - 1); err != nil {
+ return "", false, err
+ }
+ for _, kv := range a.Fields[pos:] {
+ if kv.Key() == key {
+ return kv.Value(), true, nil
+ }
+ }
+ return "", false, nil
+}
+
+func ParseAttrBody(pos token.Pos, s string) (a Attr) {
+ i := 0
+ for {
+ // always scan at least one, possibly empty element.
+ n, err := scanAttributeElem(pos, s[i:], &a)
+ if err != nil {
+ return Attr{Err: err}
+ }
+ if i += n; i >= len(s) {
+ break
+ }
+ if s[i] != ',' {
+ return Attr{Err: errors.Newf(pos, "invalid attribute: expected comma")}
+ }
+ i++
+ }
+ return a
+}
+
+func scanAttributeElem(pos token.Pos, s string, a *Attr) (n int, err errors.Error) {
+ // try CUE string
+ kv := keyValue{}
+ if n, kv.data, err = scanAttributeString(pos, s); n == 0 {
+ // try key-value pair
+ p := strings.IndexAny(s, ",=") // ) is assumed to be stripped.
+ switch {
+ case p < 0:
+ kv.data = s
+ n = len(s)
+
+ default: // ','
+ n = p
+ kv.data = s[:n]
+
+ case s[p] == '=':
+ kv.equal = p
+ offset := p + 1
+ var str string
+ if p, str, err = scanAttributeString(pos, s[offset:]); p > 0 {
+ n = offset + p
+ kv.data = s[:offset] + str
+ } else {
+ n = len(s)
+ if p = strings.IndexByte(s[offset:], ','); p >= 0 {
+ n = offset + p
+ }
+ kv.data = s[:n]
+ }
+ }
+ }
+ if a != nil {
+ a.Fields = append(a.Fields, kv)
+ }
+ return n, err
+}
+
+func scanAttributeString(pos token.Pos, s string) (n int, str string, err errors.Error) {
+ if s == "" || (s[0] != '#' && s[0] != '"' && s[0] != '\'') {
+ return 0, "", nil
+ }
+
+ nHash := 0
+ for {
+ if nHash < len(s) {
+ if s[nHash] == '#' {
+ nHash++
+ continue
+ }
+ if s[nHash] == '\'' || s[nHash] == '"' {
+ break
+ }
+ }
+ return nHash, s[:nHash], errors.Newf(pos, "invalid attribute string")
+ }
+
+ // Determine closing quote.
+ nQuote := 1
+ if c := s[nHash]; nHash+6 < len(s) && s[nHash+1] == c && s[nHash+2] == c {
+ nQuote = 3
+ }
+ close := s[nHash:nHash+nQuote] + s[:nHash]
+
+ // Search for closing quote.
+ index := strings.Index(s[len(close):], close)
+ if index == -1 {
+ return len(s), "", errors.Newf(pos, "attribute string not terminated")
+ }
+
+ index += 2 * len(close)
+ s, err2 := literal.Unquote(s[:index])
+ if err2 != nil {
+ return index, "", errors.Newf(pos, "invalid attribute string: %v", err2)
+ }
+ return index, s, nil
+}
diff --git a/internal/attrs_test.go b/internal/attrs_test.go
new file mode 100644
index 0000000..01cba60
--- /dev/null
+++ b/internal/attrs_test.go
@@ -0,0 +1,104 @@
+// Copyright 2020 CUE Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+ "fmt"
+ "strings"
+ "testing"
+
+ "cuelang.org/go/cue/token"
+)
+
+func TestAttributeBody(t *testing.T) {
+ testdata := []struct {
+ in, out string
+ err string
+ }{{
+ in: "",
+ out: "[{ 0}]",
+ }, {
+ in: "bb",
+ out: "[{bb 0}]",
+ }, {
+ in: "a,",
+ out: "[{a 0} { 0}]",
+ }, {
+ in: `"a",`,
+ out: "[{a 0} { 0}]",
+ }, {
+ in: "a,b",
+ out: "[{a 0} {b 0}]",
+ }, {
+ in: `foo,"bar",#"baz"#`,
+ out: "[{foo 0} {bar 0} {baz 0}]",
+ }, {
+ in: `bar=str`,
+ out: "[{bar=str 3}]",
+ }, {
+ in: `bar="str"`,
+ out: "[{bar=str 3}]",
+ }, {
+ in: `foo.bar="str"`,
+ out: "[{foo.bar=str 7}]",
+ }, {
+ in: `bar=,baz=`,
+ out: "[{bar= 3} {baz= 3}]",
+ }, {
+ in: `foo=1,bar="str",baz=free form`,
+ out: "[{foo=1 3} {bar=str 3} {baz=free form 3}]",
+ }, {
+ in: `"""
+ """`,
+ out: "[{ 0}]",
+ }, {
+ in: `#'''
+ \#x20
+ '''#`,
+ out: "[{ 0}]",
+ }, {
+ in: "'' ,b",
+ err: "invalid attribute",
+ }, {
+ in: "' ,b",
+ err: "not terminated",
+ }, {
+ in: `"\ "`,
+ err: "invalid attribute",
+ }, {
+ in: `# `,
+ err: "invalid attribute",
+ }}
+ for _, tc := range testdata {
+ t.Run(tc.in, func(t *testing.T) {
+ pa := ParseAttrBody(token.NoPos, tc.in)
+ err := pa.Err
+
+ if tc.err != "" {
+ if !strings.Contains(err.Error(), tc.err) {
+ t.Errorf("error was %v; want %v", err, tc.err)
+ }
+ return
+ }
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ if got := fmt.Sprint(pa.Fields); got != tc.out {
+ t.Errorf("got %v; want %v", got, tc.out)
+ }
+ })
+ }
+}
