fixes a part of #985; don't run Hexer for modules imported under when false: (#1087)

You stil get errors when imported a module under `when false:` that
causes error in nimsem.

nimsem produces `.2.deps.nif` files that doesn't contains modules
imported under `when false:`.
Nimony reads these files to generate final Makefile file so that Hexer
and later phases don't read modules imported under `when false:`.

Author: demotomohiro

src/nimony/deps.nim

@@ -28,6 +28,7 @@ type
 proc indexFile(config: NifConfig; f: FilePair): string = config.nifcachePath / f.modname & ".2.idx.nif"
 proc parsedFile(config: NifConfig; f: FilePair): string = config.nifcachePath / f.modname & ".1.nif"
 proc depsFile(config: NifConfig; f: FilePair): string = config.nifcachePath / f.modname & ".1.deps.nif"
+proc deps2File(config: NifConfig; f: FilePair): string = config.nifcachePath / f.modname & ".2.deps.nif"
 proc semmedFile(config: NifConfig; f: FilePair): string = config.nifcachePath / f.modname & ".2.nif"
 proc nifcFile(config: NifConfig; f: FilePair): string = config.nifcachePath / f.modname & ".c.nif"
 proc cFile(config: NifConfig; f: FilePair): string = config.nifcachePath / f.modname & ".c"
@@ -66,6 +67,7 @@ type
     includeStack: seq[string]
     processedModules: HashSet[string]
     moduleFlags: set[ModuleFlag]
+    isGeneratingFinal: bool
 
 proc toPair(c: DepContext; f: string): FilePair =
   FilePair(nimFile: f, modname: moduleSuffix(f, c.config.paths))
@@ -176,6 +178,7 @@ proc processDep(c: var DepContext; n: var Cursor; current: Node) =
   of ImportS:
     processImport c, n, current
   of IncludeS:
+    assert not c.isGeneratingFinal
     processInclude c, n, current
   of FromimportS, ImportexceptS:
     processSingleImport c, n, current
@@ -215,7 +218,7 @@ proc importSystem(c: var DepContext; current: Node) =
 proc parseDeps(c: var DepContext; p: FilePair; current: Node) =
   execNifler c, p.nimFile, c.config.parsedFile(p)
 
-  let depsFile = c.config.depsFile(p)
+  let depsFile = if c.isGeneratingFinal: c.config.deps2File(p) else: c.config.depsFile(p)
   var stream = nifstreams.open(depsFile)
   try:
     discard processDirectives(stream.r)
@@ -385,14 +388,17 @@ proc buildGraph*(config: sink NifConfig; project: string; forceRebuild, silentMa
       quoteShell(cfgNif)
     parseNifConfig cfgNif, config
 
-  var c = DepContext(nifler: nifler, config: config, rootNode: nil, includeStack: @[],
-    forceRebuild: forceRebuild, moduleFlags: moduleFlags, nimsem: findTool("nimsem"),
-    cmd: cmd)
-  let p = c.toPair(project)
-  c.rootNode = Node(files: @[p], id: 0, parent: -1, active: 0, isSystem: IsSystem in moduleFlags)
-  c.nodes.add c.rootNode
-  c.processedModules.incl p.modname
-  parseDeps c, p, c.rootNode
+  template initDepContext(isFinal: bool): DepContext =
+    var c = DepContext(nifler: nifler, config: config, rootNode: nil, includeStack: @[],
+      forceRebuild: forceRebuild, moduleFlags: moduleFlags, nimsem: findTool("nimsem"),
+      cmd: cmd, isGeneratingFinal: isFinal)
+    let p = c.toPair(project)
+    c.rootNode = Node(files: @[p], id: 0, parent: -1, active: 0, isSystem: IsSystem in moduleFlags)
+    c.nodes.add c.rootNode
+    c.processedModules.incl p.modname
+    parseDeps c, p, c.rootNode
+    c
+  var c = initDepContext(false)
   generateCachedConfigFile c, passC, passL
   let makeFilename = generateFrontendMakefile(c, commandLineArgs)
   #echo "run with: make -f ", makeFilename
@@ -404,6 +410,10 @@ proc buildGraph*(config: sink NifConfig; project: string; forceRebuild, silentMa
     " -f "
   exec makeCommand & quoteShell(makeFilename)
 
+  # Parse `.2.deps.nif`.
+  # It is generated by nimsem and doesn't contains modules imported under `when false:`.
+  # https://github.com/nim-lang/nimony/issues/985
+  c = initDepContext(true)
   let makeFinalFilename = generateFinalMakefile(c, commandLineArgsNifc, passC, passL)
   exec makeCommand & quoteShell(makeFinalFilename)
   if cmd == DoRun:

src/nimony/sem.nim

@@ -9,7 +9,7 @@
 ## type checking.
 
 import std / [tables, sets, syncio, formatfloat, assertions, strutils]
-from std/os import getCurrentDir
+from std/os import changeFileExt, getCurrentDir
 include nifprelude
 import nimony_model, symtabs, builtintypes, decls, symparser, asthelpers,
   programs, sigmatch, magics, reporters, nifconfig, nifindexes,
@@ -7121,6 +7121,17 @@ proc writeOutput(c: var SemContext; outfile: string) =
       toBuild: move c.toBuild,
       exportBuf: buildIndexExports(c))
 
+  # Update .2.deps.nif file that doesn't contain modules imported under `when false:`
+  # so that Hexer and following phases doesn't read such modules.
+  var deps = createTokenBuf(16)
+  deps.buildTree StmtsS, NoLineInfo:
+    if c.importedModules.len != 0:
+      deps.buildTree ImportS, NoLineInfo:
+        for _, i in c.importedModules:
+          deps.addStrLit i.path.toAbsolutePath
+  let depsFile = changeFileExt(outfile, ".deps.nif")
+  writeFile depsFile, "(.nif24)\n" & toString(deps)
+
 proc phaseX(c: var SemContext; n: Cursor; x: SemPhase): TokenBuf =
   assert n.stmtKind == StmtsS
   c.phase = x