A Location identifies a piece of source code in a .proto file which corresponds to a particular definition. This information is intended to be useful to IDEs, code indexers, documentation generators, and similar tools.
For example, say we have a file like:
message Foo {
optional string foo = 1;
}Let's look at just the field definition:
optional string foo = 1;
^ ^^ ^^ ^ ^^^
a bc de f ghiWe have the following locations:
span path represents
[a,i) [ 4, 0, 2, 0 ] The whole field definition.
[a,b) [ 4, 0, 2, 0, 4 ] The label (optional).
[c,d) [ 4, 0, 2, 0, 5 ] The type (string).
[e,f) [ 4, 0, 2, 0, 1 ] The name (foo).
[g,h) [ 4, 0, 2, 0, 3 ] The number (1).Notes:
- A location may refer to a repeated field itself (i.e. not to any particular index within it). This is used whenever a set of elements are logically enclosed in a single code segment. For example, an entire extend block (possibly containing multiple extension definitions) will have an outer location whose path refers to the "extensions" repeated field without an index.
- Multiple locations may have the same path. This happens when a single logical declaration is spread out across multiple places. The most obvious example is the "extend" block again -- there may be multiple extend blocks in the same scope, each of which will have the same path.
- A location's span is not always a subset of its parent's span. For example, the "extendee" of an extension declaration appears at the beginning of the "extend" block and is shared by all extensions within the block.
- Just because a location's span is a subset of some other location's span does not mean that it is a descendant. For example, a "group" defines both a type and a field in a single declaration. Thus, the locations corresponding to the type and field and their components will overlap.
- Code which tries to interpret locations should probably be designed to ignore those that it doesn't understand, as more types of locations could be recorded in the future.