v/vlib/v/README.md

Description

v is a namespace for all of the V compiler modules.

The V compiler modules can be used by V programs that want to process V source code in different ways, in fact, that is how various V tools are implemented: v fmt, v doc, v ast, vls, as well as the V compiler itself.

Compiler pipeline

A simple high level explanation how the compiler pipeline (parser -> checker -> generator) works.

Reading files

Getting builtin files

To load all builtin files, a preference Preferences.lookup_path for the path where to look for exists. See Builder.get_builtin_files as example. If the file is a .vsh file and the backend is C, vlib/os will also be loaded as builtin.

Getting project files

Either there is a specific file: my_file.v or a directory containing V files. In the last case it scans that directory for all files. See Builder.v_files_from_dir as the helper method. This list of files needs to be filtered so that only *.v files exist.

Skips the following file types:

• *_test.v
• either *.c.v or *.c.js depending on the backend
• all files that doesn't end with .v
• Files that are not defined in Preferences.compile_defines or Preferences.compile_defines_all if any file is defined.

Parsing files

To parse something a new template is created as the first step:

import v.ast

table := ast.new_table()

a new preference is created:

import v.pref

pref := &pref.Preferences{}

and a new scope is created:

import v.ast

scope := ast.Scope{
	parent: 0
}

after that, you can parse your files.

Parse text

If you want to parse only text which isn't saved on the disk you can use this function.

import v.parser

code := ''
// table, pref and scope needs to be passed as reference
parsed_file := parser.parse_text(code, table, .parse_comments, &pref, &scope)

Parse a single file

For parsing files on disk, a path needs to be provided. The paths are collected one step earlier.

import v.parser

path := ''
// table, pref and scope needs to be passed as reference
parsed_file := parser.parse_file(path, table, .parse_comments, &pref, &scope)

Parse a set of files

If you have a batch of paths available which should be parsed, there is also a function which does all the work.

import v.parser

paths := ['']
// table, pref and scope needs to be passed as reference
parsed_files := parser.parse_files(paths, table, &pref, &scope)

Parse imports

A file often contains imports. These imports might need to be parsed as well. The builder contains a method which does this: Builder.parse_imports.

If the module which is imported isn't parsed already, you have to collect it relatively from the main file. For this the ast.File contains a list of imports. Those imports needs to be found on disk. . is just replaced with separators in the relative location of the main file. Then all files from that directory are collected and parsed again like the previous steps explained.

Checking AST

A new checker is created:

import v.checker

mut checker := checker.new_checker(table, &pref)

After checking your files in checker.errors and checker.warnings you can see the results.

Check ast.File

checker.check(parsed_file)

Check a list of ast.File

checker.check_files(parsed_files)

Generate target from AST

Generating C code works just as this:

import v.gen.c

res := c.gen(parsed_files, table, &pref)