Add an unit test for compilation without warnings

An unit test which checks whether Nimble compiles without warnings is
added. Checking for three warning types cleaned in previous commits is
implemented:

 - [UnusedImport] cleaned in e8c7d5c

 - [Deprecated] cleaned in 3d6172e

 - [XDeclaredButNotUsed] cleaned in 7df2ef3

Other types of warnings easily can be added to the test by extending the
warnings list.

Related to #680

src/nimblepkg/nimscriptwrapper.nim

@@ -5,7 +5,7 @@
 ## scripting language.
 
 import version, options, cli, tools
-import hashes, json, os, strutils, tables, times, osproc
+import hashes, json, os, strutils, tables, times, osproc, strtabs
 
 type
   Flags = TableRef[string, seq[string]]

tests/tester.nim

@@ -1,6 +1,6 @@
 # Copyright (C) Dominik Picheta. All rights reserved.
 # BSD License. Look at license.txt for more info.
-import osproc, unittest, strutils, os, sequtils, sugar
+import osproc, unittest, strutils, os, sequtils, sugar, strformat
 
 # TODO: Each test should start off with a clean slate. Currently installed
 # packages are shared between each test which causes a multitude of issues
@@ -10,6 +10,7 @@ var rootDir = getCurrentDir().parentDir()
 var nimblePath = rootDir / "src" / addFileExt("nimble", ExeExt)
 var installDir = rootDir / "tests" / "nimbleDir"
 const path = "../src/nimble"
+const stringNotFound = -1
 
 # Clear nimble dir.
 removeDir(installDir)
@@ -863,9 +864,43 @@ test "do not install single dependency multiple times (#678)":
       check execNimble(["refresh"]).exitCode == QuitSuccess
       let (output, exitCode) = execNimble("install", "-y")
       check exitCode == QuitSuccess
-      check output.find("issue678_dependency_1@0.1.0 already exists") == -1
+      let index = output.find("issue678_dependency_1@0.1.0 already exists")
+      check index == stringNotFound
 
 test "Passing command line arguments to a task (#633)":
   cd "issue633":
     var (output, exitCode) = execNimble("testTask --testTask")
+    check exitCode == QuitSuccess
     check output.contains("Got it")
+
+test "compilation without warnings":
+  const buildDir = "./buildDir/"
+  const filesToBuild = [
+    "../src/nimble.nim",
+    "../src/nimblepkg/nimscriptapi.nim",
+    "./tester.nim",
+    ]
+
+  proc execBuild(fileName: string): tuple[output: string, exitCode: int] =
+    result = execCmdEx(fmt"nim c -o:{buildDir} {fileName}")
+
+  proc checkOutput(output: string): uint =
+    const warningsToCheck = [
+      "[UnusedImport]",
+      "[Deprecated]",
+      "[XDeclaredButNotUsed]",
+      ]
+
+    for line in output.splitLines():
+      for warning in warningsToCheck:
+        if line.find(warning) != stringNotFound:
+          once: checkpoint("Detected warnings:")
+          checkpoint(line)
+          inc(result)
+
+  var linesWithWarningsCount: uint = 0
+  for file in filesToBuild:
+    let (output, exitCode) = execBuild(file)
+    check exitCode == QuitSuccess
+    linesWithWarningsCount += checkOutput(output)
+  check linesWithWarningsCount == 0