Revert "reflect: support multiple keys in struct tags"
Proposal #40281 was initially accepted, but has now been declined.
This CL removes most of the work done to implement it.
Specifically this reverts CLs 248341, 274448, 274474, and 278392.
For #40281
For #43226
Change-Id: I5a9ebb4d9cb5fb0962434b64c59beb8343030be5
Reviewed-on: https://go-review.googlesource.com/c/go/+/281515
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
diff --git a/doc/go1.16.html b/doc/go1.16.html
index 3e564f8..3645e01 100644
--- a/doc/go1.16.html
+++ b/doc/go1.16.html
@@ -845,17 +845,6 @@
</dd>
</dl><!-- path/filepath -->
-<dl id="reflect"><dt><a href="/pkg/reflect/">reflect</a></dt>
- <dd>
- <p><!-- CL 248341, golang.org/issues/40281 -->
- <a href="/pkg/reflect/#StructTag"><code>StructTag</code></a>
- now allows multiple space-separated keys in key:value pairs,
- as in <code>`json xml:"field1"`</code> (equivalent to
- <code>`json:"field1" xml:"field1"`</code>).
- </p>
- </dd>
-</dl><!-- reflect -->
-
<dl id="runtime/debug"><dt><a href="/pkg/runtime/debug/">runtime/debug</a></dt>
<dd>
<p><!-- CL 249677 -->
diff --git a/src/reflect/all_test.go b/src/reflect/all_test.go
index b011586..1225d61 100644
--- a/src/reflect/all_test.go
+++ b/src/reflect/all_test.go
@@ -7168,176 +7168,6 @@
}
}
-func TestStructTagLookup(t *testing.T) {
- var tests = []struct {
- tag StructTag
- key string
- expectedValue string
- expectedOK bool
- }{
- {
- tag: `json:"json_value_1"`,
- key: "json",
- expectedValue: "json_value_1",
- expectedOK: true,
- },
- {
- tag: `json:"json_value_2" xml:"xml_value_2"`,
- key: "json",
- expectedValue: "json_value_2",
- expectedOK: true,
- },
- {
- tag: `json:"json_value_3" xml:"xml_value_3"`,
- key: "xml",
- expectedValue: "xml_value_3",
- expectedOK: true,
- },
- {
- tag: `bson json:"shared_value_4"`,
- key: "json",
- expectedValue: "shared_value_4",
- expectedOK: true,
- },
- {
- tag: `bson json:"shared_value_5"`,
- key: "bson",
- expectedValue: "shared_value_5",
- expectedOK: true,
- },
- {
- tag: `json bson xml form:"field_1,omitempty" other:"value_1"`,
- key: "xml",
- expectedValue: "field_1,omitempty",
- expectedOK: true,
- },
- {
- tag: `json bson xml form:"field_2,omitempty" other:"value_2"`,
- key: "form",
- expectedValue: "field_2,omitempty",
- expectedOK: true,
- },
- {
- tag: `json bson xml form:"field_3,omitempty" other:"value_3"`,
- key: "other",
- expectedValue: "value_3",
- expectedOK: true,
- },
- {
- tag: `json bson xml form:"field_4" other:"value_4"`,
- key: "json",
- expectedValue: "field_4",
- expectedOK: true,
- },
- {
- tag: `json bson xml form:"field_5" other:"value_5"`,
- key: "non_existing",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: `json "json_6"`,
- key: "json",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: `json:"json_7" bson "bson_7"`,
- key: "json",
- expectedValue: "json_7",
- expectedOK: true,
- },
- {
- tag: `json:"json_8" xml "xml_8"`,
- key: "xml",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: `json bson xml form "form_9" other:"value_9"`,
- key: "bson",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: `json bson xml form "form_10" other:"value_10"`,
- key: "other",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: `json bson xml form:"form_11" other "value_11"`,
- key: "json",
- expectedValue: "form_11",
- expectedOK: true,
- },
- {
- tag: `tag1`,
- key: "tag1",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: `tag2 :"hello_2"`,
- key: "tag2",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: `tag3: "hello_3"`,
- key: "tag3",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: "json\x7fbson: \"hello_4\"",
- key: "json",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: "json\x7fbson: \"hello_5\"",
- key: "bson",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: "json bson:\x7f\"hello_6\"",
- key: "json",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: "json bson:\x7f\"hello_7\"",
- key: "bson",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: "json\x09bson:\"hello_8\"",
- key: "json",
- expectedValue: "",
- expectedOK: false,
- },
- {
- tag: "a\x7fb json:\"val\"",
- key: "json",
- expectedValue: "",
- expectedOK: false,
- },
- }
-
- for _, test := range tests {
- v, ok := test.tag.Lookup(test.key)
- if v != test.expectedValue {
- t.Errorf("struct tag lookup failed, got %s, want %s", v, test.expectedValue)
- }
- if ok != test.expectedOK {
- t.Errorf("struct tag lookup failed, got %t, want %t", ok, test.expectedOK)
- }
- }
-}
-
// iterateToString returns the set of elements
// returned by an iterator in readable form.
func iterateToString(it *MapIter) string {
diff --git a/src/reflect/type.go b/src/reflect/type.go
index 1f1e70d..a1cdf45 100644
--- a/src/reflect/type.go
+++ b/src/reflect/type.go
@@ -1104,16 +1104,12 @@
// A StructTag is the tag string in a struct field.
//
-// By convention, tag strings are a mapping of keys to values.
-// The format is key:"value". Each key is a non-empty string consisting
-// of non-control characters other than space (U+0020 ' '),
-// quote (U+0022 '"'), and colon (U+003A ':'). Each value is quoted
-// using U+0022 '"' characters and Go string literal syntax.
-// Multiple key-value mappings are separated by zero or more spaces, as in
-// key1:"value1" key2:"value2"
-// Multiple keys may map to a single shared value by separating the keys
-// with spaces, as in
-// key1 key2:"value"
+// By convention, tag strings are a concatenation of
+// optionally space-separated key:"value" pairs.
+// Each key is a non-empty string consisting of non-control
+// characters other than space (U+0020 ' '), quote (U+0022 '"'),
+// and colon (U+003A ':'). Each value is quoted using U+0022 '"'
+// characters and Go string literal syntax.
type StructTag string
// Get returns the value associated with key in the tag string.
@@ -1136,9 +1132,6 @@
// When modifying this code, also update the validateStructTag code
// in cmd/vet/structtag.go.
- // keyFound indicates that such key on the left side has already been found.
- var keyFound bool
-
for tag != "" {
// Skip leading space.
i := 0
@@ -1158,29 +1151,11 @@
for i < len(tag) && tag[i] > ' ' && tag[i] != ':' && tag[i] != '"' && tag[i] != 0x7f {
i++
}
- if i == 0 || i+1 >= len(tag) || tag[i] < ' ' || tag[i] == 0x7f {
+ if i == 0 || i+1 >= len(tag) || tag[i] != ':' || tag[i+1] != '"' {
break
}
name := string(tag[:i])
- tag = tag[i:]
-
- // If we found a space char here - assume that we have a tag with
- // multiple keys.
- if tag[0] == ' ' {
- if name == key {
- keyFound = true
- }
- continue
- }
-
- // Spaces were filtered above so we assume that here we have
- // only valid tag value started with `:"`.
- if tag[0] != ':' || tag[1] != '"' {
- break
- }
-
- // Remove the colon leaving tag at the start of the quoted string.
- tag = tag[1:]
+ tag = tag[i+1:]
// Scan quoted string to find value.
i = 1
@@ -1196,7 +1171,7 @@
qvalue := string(tag[:i+1])
tag = tag[i+1:]
- if key == name || keyFound {
+ if key == name {
value, err := strconv.Unquote(qvalue)
if err != nil {
break
