Fix #1397: import modules beginning with a number

src/dotnet/Fable.Core/Util.fs

@@ -103,27 +103,41 @@ module Naming =
     let umdModules =
         set ["commonjs"; "amd"; "umd"]
 
-    let isIdentChar c = System.Char.IsLetterOrDigit (c) || c = '_'
+    // Dollar sign is reserved by Fable as a special character
+    // to encode other characters, unique var names and as a separator
+    let isIdentChar i (c: char) =
+        let code = int c
+        c = '_'
+        || (65 <= code && code <= 90)   // a-z
+        || (97 <= code && code <= 122)  // A-Z
+        // Digits are not allowed in first position, see #1397
+        || (i > 0 && 48 <= code && code <= 57) // 0-9
 
     let hasIdentForbiddenChars (ident: string) =
         let mutable i = 0
-        while i < ident.Length && (isIdentChar ident.[i]) do i <- i + 1
+        while i < ident.Length && (isIdentChar i ident.[i]) do i <- i + 1
         i < ident.Length
 
     let replaceIdentForbiddenChars (ident: string) =
         System.String.Concat(seq {
-            for c in ident ->
-                if isIdentChar c then string c
-                else sprintf "$%X$" (int c)
+            for i = 0 to (ident.Length - 1) do
+                let c = ident.[i]
+                if isIdentChar i c
+                then yield string c
+                else yield sprintf "$%X$" (int c)
             })
 
     let sanitizeIdentForbiddenChars (ident: string) =
         System.String(
-           [| for c in ident -> if isIdentChar c then c else '_' |] )
+           [| for i = 0 to (ident.Length - 1) do
+                let c = ident.[i]
+                if isIdentChar i c
+                then yield c else
+                yield '_' |] )
 
     let hasGenericPlaceholder (ident: string) =
         let i = ident.IndexOf(@"\$'")
-        i >= 0 && i + 2 < ident.Length && (isIdentChar ident.[i + 2])
+        i >= 0 && i + 2 < ident.Length && (isIdentChar (i + 2) ident.[i + 2])
 
     let replacePattern (prefix: string) (cond: char->bool) (repl: string->string) (str: string) =
         let rec replace (acc: string) (s: string) =
@@ -138,7 +152,7 @@ module Naming =
         replace "" str
 
     let replaceGenericPlaceholder (ident: string, onMatch: string -> string) =
-        replacePattern @"\$'" isIdentChar onMatch ident
+        replacePattern @"\$'" (isIdentChar 1) onMatch ident
 
     let replaceGenericArgsCount (ident: string, replacement: string) =
         replacePattern @"`" System.Char.IsDigit (fun _ -> replacement) ident

tests/Main/ImportTests.fs

@@ -10,13 +10,13 @@ type IFooImported =
     abstract foo: string
 
 #if FABLE_COMPILER
-[<Fable.Core.Import("*", "./js/foo.js")>]
+[<Fable.Core.Import("*", "./js/1foo.js")>]
 let fooAll: IFooImported = failwith "JS only"
 
 [<Test>]
 let ``Import with relative paths works``() =
     fooAll.foo |> equal "foo"
-    let fooAll2: IFooImported = Fable.Core.JsInterop.importAll "./js/foo.js"
+    let fooAll2: IFooImported = Fable.Core.JsInterop.importAll "./js/1foo.js"
     fooAll2.foo |> equal "foo"
 
 [<Test>]
@@ -99,7 +99,7 @@ let ``Identifiers are encoded correctly``() = // See #482
 #if FABLE_COMPILER
 open Fable.Core
 
-[<Import("MyClass", "./js/foo.js")>]
+[<Import("MyClass", "./js/1foo.js")>]
 type MyClass() =
     new (v: string) = MyClass()
     member x.value: string = jsNative
@@ -130,7 +130,7 @@ type FooOptional =
 
 [<Test>]
 let ``Only omitted optional arguments are removed``() = // See #231, #640
-    let x: FooOptional = Fable.Core.JsInterop.import "fooOptional" "./js/foo.js"
+    let x: FooOptional = Fable.Core.JsInterop.import "fooOptional" "./js/1foo.js"
     x.Foo1(5) |> equal 1
     x.Foo1(5, "3") |> equal 2
     x.Foo2(5, None) |> equal 2
@@ -139,12 +139,12 @@ let ``Only omitted optional arguments are removed``() = // See #231, #640
     x.Foo2(5,Some "3") |> equal 2
     x.Foo3(5, "3") |> equal 2
 
-let square : int -> int = JsInterop.importMember "./js/foo.js"
+let square : int -> int = JsInterop.importMember "./js/1foo.js"
 [<Test>]
 let ``Importing curried functions via `importMember` without naming arguments works`` () = // See #1185
     square 2 |> equal 4
 
-let add : int -> int -> int = JsInterop.importMember "./js/foo.js"
+let add : int -> int -> int = JsInterop.importMember "./js/1foo.js"
 [<Test>]
 let ``Importing curried functions with multiple arguments via `importMember` without naming arguments works`` () =
     add 40 2 |> equal 42

tests/Main/Util/Util.fs

@@ -16,12 +16,12 @@ module Testing =
 open Testing
 
 #if FABLE_COMPILER
-let foo: string = Fable.Core.JsInterop.importMember "../js/foo.js"
+let foo: string = Fable.Core.JsInterop.importMember "../js/1foo.js"
 
-[<Fable.Core.Import("foo", "../js/foo.js")>]
+[<Fable.Core.Import("foo", "../js/1foo.js")>]
 let foo2: string = failwith "JS only"
 
-let apply (f:Func<int,int,int>) (x:int) (y:int) = Fable.Core.JsInterop.importMember "../js/foo.js"
+let apply (f:Func<int,int,int>) (x:int) (y:int) = Fable.Core.JsInterop.importMember "../js/1foo.js"
 #else
 let foo = "foo"
 let foo2 = "foo"

tests_external/Util4.fs

@@ -3,7 +3,7 @@ module Fable.Tests.Util4
 open Fable.Core
 
 #if FABLE_COMPILER
-let foo: string = JsInterop.importMember "../tests/Main/js/foo.js"
+let foo: string = JsInterop.importMember "../tests/Main/js/1foo.js"
 
 let bar: int = JsInterop.importMember "./bar.js"