location property

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 ghi We 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.

Implementation

SourceCodeInfo class