Softened package structure rules when srcDir is not specified.

Fixes #469.

src/nimblepkg/packageparser.nim

@@ -286,6 +286,16 @@ proc inferInstallRules(pkgInfo: var PackageInfo, options: Options) =
   if installInstructions == 0 and pkgInfo.bin.len > 0:
     pkgInfo.skipExt.add("nim")
 
+  # When a package doesn't specify a `srcDir` it's fair to assume that
+  # the .nim files are in the root of the package. So we can explicitly select
+  # them and prevent the installation of anything else. The user can always
+  # override this with `installFiles`.
+  if pkgInfo.srcDir == "":
+    if dirExists(pkgInfo.getRealDir() / pkgInfo.name):
+      pkgInfo.installDirs.add(pkgInfo.name)
+    if fileExists(pkgInfo.getRealDir() / pkgInfo.name.addFileExt("nim")):
+      pkgInfo.installFiles.add(pkgInfo.name.addFileExt("nim"))
+
 proc readPackageInfo(nf: NimbleFile, options: Options,
     onlyMinimalInfo=false): PackageInfo =
   ## Reads package info from the specified Nimble file.
@@ -360,12 +370,12 @@ proc readPackageInfo(nf: NimbleFile, options: Options,
     if version.kind == verSpecial:
       result.specialVersion = minimalInfo.version
 
-  if not result.isMinimal:
-    options.pkgInfoCache[nf] = result
-
   # Apply rules to infer which files should/shouldn't be installed. See #469.
   inferInstallRules(result, options)
 
+  if not result.isMinimal:
+    options.pkgInfoCache[nf] = result
+
   # Validate the rest of the package info last.
   if not options.disableValidation:
     validateVersion(result.version)

tests/packageStructure/softened/myPkg.nimble

@@ -0,0 +1,15 @@
+# Package
+
+version       = "0.1.0"
+author        = "Dominik Picheta"
+description   = "Correctly structured package myPkg. See #469."
+license       = "MIT"
+
+# This is inferred implicitly by Nimble:
+# installDirs = @["myPkg"]
+# installFiles = @["myPkg.nim"]
+
+# Dependencies
+
+requires "nim >= 0.15.0"
+

tests/tester.nim

@@ -92,7 +92,7 @@ test "can build with #head and versioned package (#289)":
 
 test "can validate package structure (#144)":
   # Test that no warnings are produced for correctly structured packages.
-  for package in ["a", "b", "c", "validBinary"]:
+  for package in ["a", "b", "c", "validBinary", "softened"]:
     cd "packageStructure/" & package:
       let (output, exitCode) = execNimble(["install", "-y"])
       check exitCode == QuitSuccess