Add configurable NODE_PATH support and improve module resolution

.editorconfig

@@ -0,0 +1,15 @@
+#Config helps developers define and maintain consistent
+# coding styles between different editors and IDEs
+# editorconfig.org
+
+root = true
+
+[*]
+indent_style = tab
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false

README.md

@@ -84,6 +84,13 @@ autocmd User Node
   \ endif
 ```
 
+#### Want to resolve modules with a custom NODE_PATH?
+
+```vim
+let g:vim_node#node_path = [$HOME.'/project/src', '/absolute/path']
+```
+
+Or you can also start vim with the `NODE_PATH` environment variable set.
 
 License
 -------

autoload/node.vim

@@ -1,23 +1,25 @@
 " Vim by default sets the filetype to JavaScript for the following suffices.
 " And, yes, it has .jsx there.
-let node#suffixesadd = [".js", ".json", ".es", ".jsx"]
+if !exists("node#suffixesadd")
+	let node#suffixesadd = [".js", ".json", ".es", ".jsx"]
+endif
 
 function! node#initialize(root)
 	let b:node_root = a:root
 
 	command! -bar -bang -nargs=1 -buffer -complete=customlist,s:complete Nedit
-		\ exe s:nedit(<q-args>, bufname("%"), "edit<bang>")
+		\ exe s:nedit(<q-args>, expand('%:p'), "edit<bang>")
 	command! -bar -bang -nargs=1 -buffer -complete=customlist,s:complete Nopen
-		\ exe s:nopen(<q-args>, bufname("%"), "edit<bang>")
+		\ exe s:nopen(<q-args>, expand('%:p'), "edit<bang>")
 
 	nnoremap <buffer><silent> <Plug>NodeGotoFile
-		\ :call <SID>edit(expand("<cfile>"), bufname("%"))<CR>
+		\ :call <SID>edit(expand("<cfile>"), expand('%:p'))<CR>
 	nnoremap <buffer><silent> <Plug>NodeSplitGotoFile
-		\ :call <SID>edit(expand("<cfile>"), bufname("%"), "split")<CR>
+		\ :call <SID>edit(expand("<cfile>"), expand('%:p'), "split")<CR>
 	nnoremap <buffer><silent> <Plug>NodeVSplitGotoFile
-		\ :call <SID>edit(expand("<cfile>"), bufname("%"), "vsplit")<CR>
+		\ :call <SID>edit(expand("<cfile>"), expand('%:p'), "vsplit")<CR>
 	nnoremap <buffer><silent> <Plug>NodeTabGotoFile
-		\ :call <SID>edit(expand("<cfile>"), bufname("%"), "tab split")<CR>
+		\ :call <SID>edit(expand("<cfile>"), expand('%:p'), "tab split")<CR>
 
 	silent doautocmd User Node
 endfunction
@@ -30,7 +32,7 @@ function! node#javascript()
 	setlocal path-=/usr/include
 	let &l:suffixesadd .= "," . join(g:node#suffixesadd, ",")
 	let &l:include = '\<require(\(["'']\)\zs[^\1]\+\ze\1'
-	let &l:includeexpr = "node#lib#find(v:fname, bufname('%'))"
+	let &l:includeexpr = "node#lib#find(v:fname, expand('%:p'))"
 
 	" @ is used for scopes, but isn't a default filename character on
 	" non-Windows sytems.
@@ -50,13 +52,7 @@ function! s:edit(name, from, ...)
 	if empty(a:name) | return | endif
 	let dir = isdirectory(a:from) ? a:from : fnamemodify(a:from, ":h")
 	let command = a:0 == 1 ? a:1 : "edit"
-
-	" If just a plain filename with no directory part, check if it exists:
-	if a:name !~# '^\v(/|\./|\.\./)' && filereadable(dir . "/" . a:name)
-		let path = dir . "/" . a:name
-	else
-		let path = node#lib#find(a:name, dir)
-	end
+	let path = node#lib#find(a:name, dir)
 
 	if empty(path)
 		return s:error("E447: Can't find file \"" . a:name . "\" in path")

autoload/node/lib.vim

@@ -14,6 +14,20 @@ let s:CORE_MODULES = ["_debugger", "_http_agent", "_http_client",
 	\ "readline", "repl", "smalloc", "stream", "string_decoder", "sys",
 	\ "timers", "tls", "tty", "url", "util", "vm", "zlib"]
 
+" A vimscript implementation of the node.js module resolution algorithm.
+" https://nodejs.org/api/modules.html#modules_all_together
+"
+" require(a:name) from module at path a:from
+" 1. If a:name is a core module,
+"		a. return the core module
+"		b. STOP
+" 2. If a:name begins with '/'
+"		a. set a:from to be the filesystem root
+" 3. If a:name begins with './' or '/' or '../'
+"		a. LOAD_AS_FILE(a:from + a:name)
+"		b. LOAD_AS_DIRECTORY(a:from + a:name)
+" 4. LOAD_NODE_MODULES(a:name, dirname(a:from))
+" 5. THROW "not found"
 function! node#lib#find(name, from)
 	if index(s:CORE_MODULES, a:name) != -1
 		let l:version = node#lib#version()
@@ -22,39 +36,47 @@ function! node#lib#find(name, from)
 		return s:CORE_URL_PREFIX ."/". l:version ."/". l:dir ."/". a:name .".js"
 	endif
 
-	return s:resolve(s:absolutize(a:name, a:from))
-endfunction
+	let request = s:getModulePath(a:name, a:from)
+	if !empty(request)
+		let asFile = s:loadAsFile(request)
+		if !empty(asFile) | return resolve(asFile) | endif
 
-function! node#lib#version()
-	if exists("b:node_version") | return b:node_version | endif
-	if !executable("node") | let b:node_version = "" | return | endif
-	let b:node_version = matchstr(system("node --version"), '^v\?\zs[0-9.]\+')
-	return b:node_version
-endfunction
-
-function! s:absolutize(name, from)
-	if a:name =~# s:ABSPATH
-		return a:name
-	elseif a:name =~# s:RELPATH
-		let dir = isdirectory(a:from) ? a:from : fnamemodify(a:from, ":h")
-		return dir . "/" . a:name
-	else
-		return b:node_root . "/node_modules/" . a:name
+		let asDirectory = s:loadAsDirectory(request)
+		if !empty(asDirectory) | return resolve(asDirectory) | endif
 	endif
+
+	let asNodeModule = s:loadNodeModules(a:name, s:dirname(a:from))
+	if !empty(asNodeModule) | return resolve(asNodeModule) | endif
 endfunction
 
-function! s:resolve(path)
-	" Node checks for files *before* directories, so see if the path does not
-	" end with a slash or dots and try to match it as a file.
+" LOAD_AS_FILE(X)
+" 1. If X is a file, load X as JavaScript text.	STOP
+" 2. If X.js is a file, load X.js as JavaScript text.	STOP
+" 3. If X.json is a file, parse X.json to a JavaScript Object.	STOP
+" 4. If X.node is a file, load X.node as binary addon.	STOP
+function! s:loadAsFile(path)
 	if a:path !~# '\v/(\.\.?/?)?$'
 		let path_with_suffix = s:resolveSuffix(a:path)
 		if !empty(path_with_suffix) | return path_with_suffix | endif
 	endif
+endfunction
 
-	if isdirectory(a:path) | return s:resolveFromDirectory(a:path) | endif
+" LOAD_INDEX(X)
+" 1. If X/index.js is a file, load X/index.js as JavaScript text.	STOP
+" 2. If X/index.json is a file, parse X/index.json to a JavaScript object. STOP
+" 3. If X/index.node is a file, load X/index.node as binary addon.	STOP
+function! s:loadIndex(path)
+	return s:resolveSuffix(a:path . "/index")
 endfunction
 
-function! s:resolveFromDirectory(path)
+" LOAD_AS_DIRECTORY(X)
+" 1. If X/package.json is a file,
+"		a. Parse X/package.json, and look for "main" field.
+"		b. let M = X + (json main field)
+"		c. LOAD_AS_FILE(M)
+"		d. LOAD_INDEX(M)
+" 2. LOAD_INDEX(X)
+function! s:loadAsDirectory(path)
 	" Node.js checks for package.json in every directory, not just the
 	" module's parent. According to:
 	" http://nodejs.org/api/modules.html#modules_all_together
@@ -66,17 +88,94 @@ function! s:resolveFromDirectory(path)
 		let main = s:mainFromPackage(a:path . "/package.json")
 
 		if !empty(main) && main != ""
-			let path = s:resolve(a:path . "/" . main)
-			if !empty(path) | return path | endif
+			let path = a:path . "/" . main
+			let asFile = s:loadAsFile(path)
+			if !empty(asFile) | return asFile | endif
+
+			let asIndex = s:loadIndex(path)
+			if !empty(asIndex) | return asIndex | endif
 		endif
 	endif
 
-	" We need to check for ./index.js's existence here rather than leave it to
-	" the caller, because otherwise we can't distinguish if this ./index was
-	" from the directory defaulting to ./index.js or it was the package.json
-	" which referred to ./index, which in itself could mean both ./index.js and
-	" ./index/index.js.
-	return s:resolveSuffix(a:path . "/index")
+	return s:loadIndex(a:path)
+endfunction
+
+" LOAD_NODE_MODULES(X, START)
+" 1. let DIRS=NODE_MODULES_PATHS(START)
+" 2. for each DIR in DIRS:
+"		a. LOAD_AS_FILE(DIR/X)
+"		b. LOAD_AS_DIRECTORY(DIR/X)
+function! s:loadNodeModules(x, start)
+	let dirs = s:nodeModulePaths(a:start)
+	for dir in dirs
+		let path = dir . "/" . a:x
+		let asFile = s:loadAsFile(path)
+		if !empty(asFile) | return asFile | endif
+
+		let asDirectory = s:loadAsDirectory(path)
+		if !empty(asDirectory) | return asDirectory | endif
+	endfor
+endfunction
+
+" NODE_MODULES_PATHS(START)
+" 1. let PARTS = path split(START)
+" 2. let I = count of PARTS - 1
+" 3. let DIRS = []
+" 4. while I >= 0,
+"		a. if PARTS[I] = "node_modules" CONTINUE
+"		b. DIR = path join(PARTS[0 .. I] + "node_modules")
+"		c. DIRS = DIRS + DIR
+"		d. let I = I - 1
+" 5. return DIRS
+function! s:nodeModulePaths(start)
+	let parts = split(a:start, '/')
+
+	" We want to keep the leading slash of an absolute path
+	if a:start =~# s:ABSPATH
+		let parts[0] = '/' . parts[0]
+	endif
+
+	let i = len(parts) - 1
+	let dirs = []
+	while i >= 0
+		if parts[i] == 'node_modules' | continue | endif
+		let dir = join(parts[0:i] + ['node_modules'], '/')
+		let dirs += [dir]
+		let i = i - 1
+	endwhile
+
+	" Add support for NODE_PATH
+	let NODE_PATH = $NODE_PATH
+	if !empty(NODE_PATH)
+		let dirs += [NODE_PATH]
+	endif
+
+	" Add support for configured NODE_PATH
+	if !empty(g:vim_node#node_path)
+		let dirs += g:vim_node#node_path
+	endif
+
+	return dirs
+endfunction
+
+function! s:getModulePath(name, from)
+	if a:name =~# s:ABSPATH
+		return a:name
+	elseif a:name =~# s:RELPATH
+		let dir = isdirectory(a:from) ? a:from : s:dirname(a:from)
+		return dir . "/" . a:name
+	endif
+endfunction
+
+function! s:dirname(path)
+	return fnamemodify(a:path, ':h')
+endfunction
+
+function! node#lib#version()
+	if exists("b:node_version") | return b:node_version | endif
+	if !executable("node") | let b:node_version = "" | return | endif
+	let b:node_version = matchstr(system("node --version"), '^v\?\zs[0-9.]\+')
+	return b:node_version
 endfunction
 
 function! s:mainFromPackage(path)