gogrep's Introduction

gogrep

GO111MODULE=on go get mvdan.cc/gogrep

Search for Go code using syntax trees. Work in progress.

gogrep -x 'if $x != nil { return $x, $*_ }'

Instructions

usage: gogrep commands [packages]

A command is of the form "-A pattern", where -A is one of:

   -x  find all nodes matching a pattern
   -g  discard nodes not matching a pattern
   -v  discard nodes matching a pattern
   -a  filter nodes by certain attributes
   -s  substitute with a given syntax tree
   -w  write source back to disk or stdout

A pattern is a piece of Go code which may include wildcards. It can be:

   a statement (many if split by semicolons)
   an expression (many if split by commas)
   a type expression
   a top-level declaration (var, func, const)
   an entire file

Wildcards consist of $ and a name. All wildcards with the same name within an expression must match the same node, excluding "_". Example:

   $x.$_ = $x // assignment of self to a field in self

If * is before the name, it will match any number of nodes. Example:

   fmt.Fprintf(os.Stdout, $*_) // all Fprintfs on stdout

* can also be used to match optional nodes, like:

for $*_ { $*_ }    // will match all for loops
if $*_; $b { $*_ } // will match all ifs with condition $b

The nodes resulting from applying the commands will be printed line by line to standard output.

Here are two simple examples of the -a operand:

   gogrep -x '$x + $y'                   // will match both numerical and string "+" operations
   gogrep -x '$x + $y' -a 'type(string)' // matches only string concatenations

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