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127 lines
4 KiB
Markdown
127 lines
4 KiB
Markdown
lua-parser
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==========
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[](https://travis-ci.org/andremm/lua-parser)
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This is a Lua 5.3 parser written with [LPegLabel](https://github.com/sqmedeiros/lpeglabel) that
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generates an AST in a format that is similar to the one specified by [Metalua](https://github.com/fab13n/metalua-parser).
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The parser uses LPegLabel to provide more specific error messages.
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Requirements
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------------
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lua >= 5.1
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lpeglabel >= 1.0.0
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API
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---
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The package `lua-parser` has two modules: `lua-parser.parser`
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and `lua-parser.pp`.
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The module `lua-parser.parser` implements the function `parser.parse`:
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* `parser.parse (subject, filename)`
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Both subject and filename should be strings.
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It tries to parse subject and returns the AST in case of success.
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It returns **nil** plus an error message in case of error.
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In case of error, the parser uses the string filename to build an
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error message.
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The module `lua-parser.pp` implements a pretty printer to the AST and
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a dump function:
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* `pp.tostring (ast)`
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It converts the AST to a string and returns this string.
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* `pp.print (ast)`
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It converts the AST to a string and prints this string.
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* `pp.dump (ast[, i])`
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It dumps the AST to the screen.
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The parameter **i** sets the indentation level.
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AST format
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----------
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block: { stat* }
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stat:
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`Do{ stat* }
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| `Set{ {lhs+} {expr+} } -- lhs1, lhs2... = e1, e2...
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| `While{ expr block } -- while e do b end
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| `Repeat{ block expr } -- repeat b until e
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| `If{ (expr block)+ block? } -- if e1 then b1 [elseif e2 then b2] ... [else bn] end
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| `Fornum{ ident expr expr expr? block } -- for ident = e, e[, e] do b end
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| `Forin{ {ident+} {expr+} block } -- for i1, i2... in e1, e2... do b end
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| `Local{ {ident+} {expr+}? } -- local i1, i2... = e1, e2...
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| `Localrec{ ident expr } -- only used for 'local function'
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| `Goto{ <string> } -- goto str
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| `Label{ <string> } -- ::str::
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| `Return{ <expr*> } -- return e1, e2...
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| `Break -- break
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| apply
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expr:
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`Nil
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| `Dots
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| `Boolean{ <boolean> }
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| `Number{ <number> }
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| `String{ <string> }
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| `Function{ { `Id{ <string> }* `Dots? } block }
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| `Table{ ( `Pair{ expr expr } | expr )* }
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| `Op{ opid expr expr? }
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| `Paren{ expr } -- significant to cut multiple values returns
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| apply
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| lhs
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apply:
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`Call{ expr expr* }
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| `Invoke{ expr `String{ <string> } expr* }
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lhs: `Id{ <string> } | `Index{ expr expr }
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opid: -- includes additional operators from Lua 5.3 and all relational operators
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'add' | 'sub' | 'mul' | 'div'
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| 'idiv' | 'mod' | 'pow' | 'concat'
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| 'band' | 'bor' | 'bxor' | 'shl' | 'shr'
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| 'eq' | 'ne' | 'lt' | 'gt' | 'le' | 'ge'
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| 'and' | 'or' | 'unm' | 'len' | 'bnot' | 'not'
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Usage
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--------
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**Code example for parsing a string:**
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local parser = require "lua-parser.parser"
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local pp = require "lua-parser.pp"
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if #arg ~= 1 then
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print("Usage: parse.lua <string>")
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os.exit(1)
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end
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local ast, error_msg = parser.parse(arg[1], "example.lua")
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if not ast then
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print(error_msg)
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os.exit(1)
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end
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pp.print(ast)
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os.exit(0)
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**Running the above code example using a string without syntax error:**
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$ lua parse.lua "for i=1, 10 do print(i) end"
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{ `Fornum{ `Id "i", `Number "1", `Number "10", { `Call{ `Id "print", `Id "i" } } } }
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**Running the above code example using a string with syntax error:**
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$ lua parse.lua "for i=1, 10 do print(i) "
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example.lua:1:24: syntax error, expected 'end' to close the for loop
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