$(a: float) now works consistently in nim js, avoiding printing floats as ints (#14134)

* fix https://github.com/timotheecour/Nim/issues/133; $(a: float) works in nim js like in other backends

* fix tests

* fix test for windows that prints 1.1e17 differently than other OS

compiler/jsgen.nim

@@ -530,11 +530,10 @@ proc arithAux(p: PProc, n: PNode, r: var TCompRes, op: TMagic) =
     gen(p, n[1], r)
     xLoc = r.rdLoc
 
-  template applyFormat(frmtA, frmtB: string) =
-    if i == 0:
-      r.res = frmtA % [xLoc, yLoc]
-    else:
-      r.res = frmtB % [xLoc, yLoc]
+  template applyFormat(frmt) =
+    r.res = frmt % [xLoc, yLoc]
+  template applyFormat(frmtA, frmtB) =
+    if i == 0: applyFormat(frmtA) else: applyFormat(frmtB)
 
   case op:
   of mAddI: applyFormat("addInt($1, $2)", "($1 + $2)")
@@ -596,7 +595,9 @@ proc arithAux(p: PProc, n: PNode, r: var TCompRes, op: TMagic) =
   of mBoolToStr: applyFormat("nimBoolToStr($1)", "nimBoolToStr($1)")
   of mIntToStr: applyFormat("cstrToNimstr(($1)+\"\")", "cstrToNimstr(($1)+\"\")")
   of mInt64ToStr: applyFormat("cstrToNimstr(($1)+\"\")", "cstrToNimstr(($1)+\"\")")
-  of mFloatToStr: applyFormat("cstrToNimstr(($1)+\"\")", "cstrToNimstr(($1)+\"\")")
+  of mFloatToStr:
+    useMagic(p, "nimFloatToString")
+    applyFormat "cstrToNimstr(nimFloatToString($1))"
   of mCStrToStr: applyFormat("cstrToNimstr($1)", "cstrToNimstr($1)")
   of mStrToStr, mUnown: applyFormat("$1", "$1")
   else:

lib/system/jssys.nim

@@ -476,6 +476,21 @@ proc negInt(a: int): int {.compilerproc.} =
 proc negInt64(a: int64): int64 {.compilerproc.} =
   result = a*(-1)
 
+proc nimFloatToString(a: float): cstring {.compilerproc.} =
+  ## ensures the result doesn't print like an integer, ie return 2.0, not 2
+  asm """
+    function nimOnlyDigitsOrMinus(n) {
+      return n.toString().match(/^-?\d+$/);
+    }
+    if (Number.isSafeInteger(`a`)) `result` =  `a`+".0"
+    else {
+      `result` = `a`+""
+      if(nimOnlyDigitsOrMinus(`result`)){
+        `result` = `a`+".0"
+      }
+    }
+  """
+
 proc absInt(a: int): int {.compilerproc.} =
   result = if a < 0: a*(-1) else: a
 

tests/js/tbyvar.nim

@@ -1,15 +1,16 @@
 discard """
-  output: '''foo 12
+  output: '''
+foo 12
 bar 12
 2
 foo 12
 bar 12
 2
 12.5
-(nums: @[5, 5, 10, 5, 5, 5, 5, 5, 5, 5])
-(nums: @[5, 5, 50, 5, 5, 5, 5, 5, 5, 5])
-(nums: @[5, 5, 45, 5, 5, 5, 5, 5, 5, 5])
-(nums: @[5, 5, 9, 5, 5, 5, 5, 5, 5, 5])
+(nums: @[5.0, 5.0, 10.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0])
+(nums: @[5.0, 5.0, 50.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0])
+(nums: @[5.0, 5.0, 45.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0])
+(nums: @[5.0, 5.0, 9.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0])
 asd
 '''
 """

tests/js/tdollar_float.nim

@@ -0,0 +1,62 @@
+#[
+merge into tests/system/tdollars.nim once https://github.com/nim-lang/Nim/pull/14122
+is merged
+]#
+
+import unittest
+
+block: # https://github.com/timotheecour/Nim/issues/133
+  # simple test
+  var a: float = 2
+  check $a == "2.0"
+
+  # systematic tests
+  template fun(a2: static float) =
+    const a: float = a2 # needed pending https://github.com/timotheecour/Nim/issues/132
+    var b = a
+    check $b == $a
+
+  fun 2
+  fun 2.0
+  fun 2.1
+  fun 1_000
+  fun 1_000.1
+  fun 1_000_000_000.1
+  fun 1_000_000_000_000.1
+
+  # negatives
+  fun -2.0
+  fun -2.1
+
+  # 0
+  fun 0
+  fun -0
+  fun 0.0
+
+  block:
+    var a = -0.0
+    check $a in ["-0.0", "0.0"]
+
+  # exponents
+  block:
+    var a = 5e20
+    check $a in ["5e20", "500000000000000000000.0"]
+
+  fun 3.4e1'f32
+  fun 3.4e-1'f32
+  fun -3.4e-1'f32
+  fun 3.4e-1'f32
+  fun 3e-1'f32
+
+  block:
+    var a = 3.4e38'f32
+    check $a in ["3.4e+38", "3.4e+038"]
+      # on windows, printf (used in VM) prints as 3.4e+038
+      # but js prints as 3.4e+38
+      # on osx, both print as 3.4e+38
+      # see https://github.com/timotheecour/Nim/issues/138
+
+  when false: # edge cases
+    fun -0.0 # see https://github.com/timotheecour/Nim/issues/136
+    fun 5e20
+    fun 3.4e38'f32