Python support for Fable 🎉

build.fsx

@@ -170,6 +170,32 @@ let buildLibraryTs() =
     runInDir buildDirTs "npm run tsc -- --init --target es2020 --module es2020 --allowJs"
     runInDir buildDirTs ("npm run tsc -- --outDir ../../" + buildDirJs)
 
+let buildLibraryPy() =
+    let libraryDir = "src/fable-library-py"
+    let projectDir = libraryDir + "/fable"
+    let buildDirPy = "build/fable-library-py"
+
+    cleanDirs [buildDirPy]
+
+    runFableWithArgs projectDir [
+        "--outDir " + buildDirPy </> "fable"
+        "--fableLib " + buildDirPy </> "fable"
+        "--lang Python"
+        "--exclude Fable.Core"
+    ]
+    // Copy *.py from projectDir to buildDir
+    copyDirRecursive libraryDir buildDirPy
+    copyDirNonRecursive (buildDirPy </> "fable/fable-library") (buildDirPy </> "fable")
+    //copyFile (buildDirPy </> "fable/fable-library/*.py") (buildDirPy </> "fable")
+    copyFile (buildDirPy </> "fable/system.text.py") (buildDirPy </> "fable/system_text.py")
+    copyFile (buildDirPy </> "fable/fsharp.core.py") (buildDirPy </> "fable/fsharp_core.py")
+    copyFile (buildDirPy </> "fable/fsharp.collections.py") (buildDirPy </> "fable/fsharp_collections.py")
+    //copyFile (buildDirPy </> "fable/async.py") (buildDirPy </> "fable/async_.py")
+    removeFile (buildDirPy </> "fable/system.text.py")
+
+    runInDir buildDirPy ("python3 --version")
+    runInDir buildDirPy ("python3 ./setup.py develop")
+
 // Like testJs() but doesn't create bundles/packages for fable-standalone & friends
 // Mainly intended for CI
 let testJsFast() =
@@ -368,6 +394,24 @@ let test() =
     if envVarOrNone "APPVEYOR" |> Option.isSome then
         testJsFast()
 
+let testPython() =
+    buildLibraryIfNotExists() // NOTE: fable-library-py needs to be built seperatly.
+
+    let projectDir = "tests/Python"
+    let buildDir = "build/tests/Python"
+
+    cleanDirs [buildDir]
+    runInDir projectDir "dotnet test"
+    runFableWithArgs projectDir [
+        "--outDir " + buildDir
+        "--exclude Fable.Core"
+        "--lang Python"
+    ]
+
+    runInDir buildDir "touch __init__.py" // So relative imports works.
+    runInDir buildDir "pytest"
+
+
 let buildLocalPackageWith pkgDir pkgCommand fsproj action =
     let version = "3.0.0-local-build-" + DateTime.Now.ToString("yyyyMMdd-HHmm")
     action version
@@ -525,9 +569,16 @@ match argsLower with
 | "test-react"::_ -> testReact()
 | "test-compiler"::_ -> testCompiler()
 | "test-integration"::_ -> testIntegration()
+| "test-py"::_ -> testPython()
 | "quicktest"::_ ->
     buildLibraryIfNotExists()
-    run "dotnet watch -p src/Fable.Cli run -- watch --cwd ../quicktest --exclude Fable.Core --noCache --runScript"
+    run "dotnet watch -p src/Fable.Cli run -- watch --cwd ../quicktest --exclude Fable.Core --noCache"
+| "quicktest-py"::_ ->
+    buildLibraryIfNotExists()
+    run "dotnet watch -p src/Fable.Cli run -- watch --cwd ../quicktest --lang Python --exclude Fable.Core --noCache"
+| "jupyter" :: _ ->
+    buildLibraryIfNotExists ()
+    run "dotnet watch -p src/Fable.Cli run -- watch --cwd /Users/dbrattli/Developer/GitHub/Fable.Jupyter/src --lang Python --exclude Fable.Core --noCache 2>> /Users/dbrattli/Developer/GitHub/Fable.Jupyter/src/fable.out"
 
 | "run"::_ ->
     buildLibraryIfNotExists()
@@ -546,6 +597,7 @@ match argsLower with
 | ("watch-library")::_ -> watchLibrary()
 | ("fable-library"|"library")::_ -> buildLibrary()
 | ("fable-library-ts"|"library-ts")::_ -> buildLibraryTs()
+| ("fable-library-py"|"library-py")::_ -> buildLibraryPy()
 | ("fable-compiler-js"|"compiler-js")::_ -> buildCompilerJs(minify)
 | ("fable-standalone"|"standalone")::_ -> buildStandalone {|minify=minify; watch=false|}
 | "watch-standalone"::_ -> buildStandalone {|minify=false; watch=true|}
@@ -572,4 +624,4 @@ match argsLower with
     dotnet fsi build.fsx quicktest
 """
 
-printfn "Build finished successfully"
+printfn "Build finished successfully"

src/Fable.AST/Plugins.fs

@@ -12,6 +12,7 @@ type Verbosity =
 type Language =
     | JavaScript
     | TypeScript
+    | Python
     | Php
 
 type CompilerOptions =

src/Fable.Cli/Entry.fs

@@ -75,8 +75,8 @@ Arguments:
   --sourceMapsRoot  Set the value of the `sourceRoot` property in generated source maps
 
   --optimize        Compile with optimized F# AST (experimental)
-  --lang|--language Compile to JavaScript (default), "TypeScript" or "Php".
-                    Support for TypeScript and Php is experimental.
+  --lang|--language Compile to JavaScript (default), TypeScript, Php or Python.
+                    Support for TypeScript, Php and Python is experimental.
 
   Environment variables:
    DOTNET_USE_POLLING_FILE_WATCHER
@@ -92,6 +92,7 @@ let defaultFileExt language args =
         | None -> CompilerOptionsHelper.DefaultExtension
     match language with
     | TypeScript -> Path.replaceExtension ".ts" fileExt
+    | Python -> Path.replaceExtension ".py" fileExt
     | Php -> ".php"
     | _ -> fileExt
 
@@ -102,6 +103,7 @@ let argLanguage args =
     |> Option.defaultValue "JavaScript"
     |> (function
     | "ts" | "typescript" | "TypeScript" -> TypeScript
+    | "py" | "python" | "Python" -> Python
     | "php" | "Php" | "PHP" -> Php
     | _ -> JavaScript)
 

src/Fable.Cli/Main.fs

@@ -166,6 +166,29 @@ module private Util =
         member _.SourceMap =
             mapGenerator.Force().toJSON()
 
+    type PythonFileWriter(sourcePath: string, targetPath: string, cliArgs: CliArgs, dedupTargetDir) =
+        let fileExt = ".py"
+        let targetDir = Path.GetDirectoryName(targetPath)
+        // PEP8: Modules should have short, all-lowercase names
+        let fileName = Path.GetFileNameWithoutExtension(Path.GetFileNameWithoutExtension(targetPath))
+        let fileName = Naming.applyCaseRule Core.CaseRules.SnakeCase fileName
+        // Note that Python modules cannot contain dots or it will be impossible to import them
+        let targetPath = Path.Combine(targetDir, fileName + fileExt)
+
+        let stream = new IO.StreamWriter(targetPath)
+
+        interface PythonPrinter.Writer with
+            member _.Write(str) =
+                stream.WriteAsync(str) |> Async.AwaitTask
+            member _.MakeImportPath(path) =
+                let projDir = IO.Path.GetDirectoryName(cliArgs.ProjectFile)
+                let path = Imports.getImportPath dedupTargetDir sourcePath targetPath projDir cliArgs.OutDir path
+                if path.EndsWith(".fs") then
+                    let isInFableHiddenDir = Path.Combine(targetDir, path) |> Naming.isInFableHiddenDir
+                    changeFsExtension isInFableHiddenDir path "" // Remove file extension
+                else path
+            member _.Dispose() = stream.Dispose()
+
     let compileFile isRecompile (cliArgs: CliArgs) dedupTargetDir (com: CompilerImpl) = async {
         try
             let fable =
@@ -194,12 +217,18 @@ module private Util =
 
             | Php ->
                 let php = fable |> Fable2Php.transformFile com
-                
+
                 use w = new IO.StreamWriter(outPath)
                 let ctx = PhpPrinter.Output.Writer.create w
                 PhpPrinter.Output.writeFile ctx php
                 w.Flush()
 
+            | Python ->
+                let python = fable |> Fable2Python.Compiler.transformFile com
+                let map = { new PythonPrinter.SourceMapGenerator with
+                                member _.AddMapping(_,_,_,_,_) = () }
+                let writer = new PythonFileWriter(com.CurrentFile, outPath, cliArgs, dedupTargetDir)
+                do! PythonPrinter.run writer map python
 
             "Compiled " + File.getRelativePathFromCwd com.CurrentFile
             |> Log.verboseOrIf isRecompile

src/Fable.Core/Fable.Core.JsInterop.fs

@@ -70,6 +70,10 @@ let jsTypeof (x: obj): string = jsNative
 [<Emit("$0 instanceof $1")>]
 let jsInstanceof (x: obj) (cons: obj): bool = jsNative
 
+/// Check if object is callable, i.e a function.
+[<Emit("typeof $0 == \"function\"")>]
+let inline callable(x: obj) = jsNative
+
 [<Emit("this")>]
 let jsThis<'T> : 'T = jsNative