这是什么一个叹号YAML吗? [英] What does a single exclamation mark do in YAML?
问题描述
我的工作与 YamlDotNet 图书馆,我加载YAML文件时,收到此错误:
在解析一个标记,没有找到预期的标签URI。
在YAML文件应该是良好的,因为它涉及直接从回报率。错误似乎是由这个code触发:
格式:
默认: ! %D-%M-%Y'
长: ! %D%B,%Y'
短: ! %D%B'
我不是专家,但我从YAML规范,您可以使用感叹号,表示自定义对象/类型看,和两个感叹号,表明一个明确的内置式。
OBJ1:自定义#什么
OBJ2:!! STR我的字符串
不过,我一直没能找到任何提及作为上述感叹号。这是什么意思,为什么YAML库我使用似乎并没有能够解析呢?需要注意的是,如果我删除这些感叹号,将解析该文件的罚款。
这!是非特异性标签。
通过明确地指定一个!非特定标签属性,节点 将被解析为一个香草的序列,映射,或字符串, 从其类。
看看这里标签语法:
无:未指定标签(由应用程序自动解决)。 ! :非特异性标记(默认情况下,!!图/!序列/!!海峡)。 '富!:主(按照惯例,这意味着一个局部变量富!)。 '!!富':中学(按照惯例,意思是标签:yaml.org,2002:富)。 !^ h富':需要%TAG H< preFIX>! (然后表示< preFIX>富)。 !<富>':威宝标签(通常意味着富)。
为什么YamlDotNet抛出一个错误?我不能100%肯定,但我认为你发现了一个bug。
YamlDotNet是 LibYAML 的端口,所以很容易进行比较的来源。
scanner.c 2635线(LibYAML):
/ *检查标签非空。 * /
如果(!长){
Scanner.cs 2146线(YamlDotNet):
//检查标签非空。
如果(tag.Length == 0)
我知道,这两个看起来非常相似,但在这一点长度
1和 tag.Length
0 。原来的C code照顾最初的! (全长),但C#不这样做(只是标签名的长度)。
文件中的问题的项目。
I'm working with the YamlDotNet library and I'm getting this error when loading a YAML file:
While parsing a tag, did not find expected tag URI.
The YAML file is supposed to be well-formed because it comes right from RoR. The error seems to be triggered by this code:
formats:
default: ! '%d-%m-%Y'
long: ! '%d %B, %Y'
short: ! '%d %b'
I'm not an expert, but I see from the YAML spec that you can use an exclamation mark to indicate a custom object/type, and two exclamation marks to indicate an explicit built-in type.
obj1: !custom # whatever
obj2: !!str "My string"
However I haven't been able to find any reference to an exclamation mark used as above. What does that mean, and why the YAML library I use doesn't seem able to parse it? Note that if I remove those exclamation marks, the file is parsed fine.
That "!" is the "non-specific tag".
YAML specification 1.2 stays (also 1.1):
By explicitly specifying a "!" non-specific tag property, the node would then be resolved to a "vanilla" sequence, mapping, or string, according to its kind.
Take a look here to the tag "grammar":
none : Unspecified tag (automatically resolved by application). '!' : Non-specific tag (by default, "!!map"/"!!seq"/"!!str"). '!foo' : Primary (by convention, means a local "!foo" tag). '!!foo' : Secondary (by convention, means "tag:yaml.org,2002:foo"). '!h!foo': Requires "%TAG !h! <prefix>" (and then means "<prefix>foo"). '!<foo>': Verbatim tag (always means "foo").
Why is YamlDotNet throwing a error? I can't be 100% sure, but I think you found a bug.
YamlDotNet is a port of LibYAML, so it's easy to compare sources.
Line 2635 of scanner.c (LibYAML):
/* Check if the tag is non-empty. */
if (!length) {
Line 2146 of Scanner.cs (YamlDotNet ):
// Check if the tag is non-empty.
if (tag.Length == 0)
I know, both looks very similar, but at this point length
is 1 and tag.Length
is 0. Original C code takes care of the initial "!" (whole length) but C# doesn't do it (just the tag "name" length).
File an issue to the project.
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