From 3502eaf3bd44a9a2ec22a17e99238afee16dd3f8 Mon Sep 17 00:00:00 2001
From: Mischa Holz <me@mhlz.de>
Date: Fri, 26 Sep 2025 21:52:02 +0200
Subject: [PATCH 1/4] Make new BigDecimal produce better errors

---
 src/BigDecimal.test.ts       |  22 ++++++++++++++++++
 src/BigDecimal.test.ts.md    |  44 +++++++++++++++++++++++++++++++++++
 src/BigDecimal.test.ts.snap  | Bin 243 -> 443 bytes
 src/BigDecimal.ts            |  15 ++++++++++--
 src/collections.test.ts.snap | Bin 642 -> 644 bytes
 5 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/src/BigDecimal.test.ts b/src/BigDecimal.test.ts
index bb2b35f..7f00726 100644
--- a/src/BigDecimal.test.ts
+++ b/src/BigDecimal.test.ts
@@ -32,6 +32,28 @@ function testUnnecessary(
   }
 }
 
+test("BigDecimal parsing", (t) => {
+  const passes = new BigDecimal("1.1")
+  t.is(passes.toString(), "1.1")
+  t.is(passes.scale(), 1)
+  t.is(passes.unscaledValue(), 11n)
+
+  let e = t.throws(() => new BigDecimal("1.1.1"))
+  t.snapshot(e, "too many decimal places")
+  e = t.throws(() => new BigDecimal("1.1e1"))
+  t.snapshot(e, "weird exponential notation")
+  e = t.throws(() => new BigDecimal("1.1e10"))
+  t.snapshot(e, "normal exponential notation")
+  e = t.throws(() => new BigDecimal("1.1e"))
+  t.snapshot(e, "other weird exponential notation")
+  e = t.throws(() => new BigDecimal("1.1e1.1"))
+  t.snapshot(e, "super weird exponential notation")
+  e = t.throws(() => new BigDecimal("abcd"))
+  t.snapshot(e, "not a number")
+  e = t.throws(() => new BigDecimal("zxy"))
+  t.snapshot(e, "another not a number")
+})
+
 test("BigDecimal rounding", (t) => {
   testRounding(t, "5.5", "6", {
     precision: 0,
diff --git a/src/BigDecimal.test.ts.md b/src/BigDecimal.test.ts.md
index 1cc2e4f..9825cb6 100644
--- a/src/BigDecimal.test.ts.md
+++ b/src/BigDecimal.test.ts.md
@@ -4,6 +4,50 @@ The actual snapshot is saved in `BigDecimal.test.ts.snap`.
 
 Generated by [AVA](https://avajs.dev).
 
+## BigDecimal parsing
+
+> too many decimal places
+
+    Error {
+      message: 'BigDecimal: too many decimal places',
+    }
+
+> weird exponential notation
+
+    Error {
+      message: 'BigDecimal: exponential notation is not supported',
+    }
+
+> normal exponential notation
+
+    Error {
+      message: 'BigDecimal: exponential notation is not supported',
+    }
+
+> other weird exponential notation
+
+    Error {
+      message: 'BigDecimal: exponential notation is not supported',
+    }
+
+> super weird exponential notation
+
+    Error {
+      message: 'BigDecimal: exponential notation is not supported',
+    }
+
+> not a number
+
+    Error {
+      message: 'BigDecimal: not a number',
+    }
+
+> another not a number
+
+    Error {
+      message: 'BigDecimal: not a number',
+    }
+
 ## BigDecimal.compareTo
 
 > Snapshot 1
diff --git a/src/BigDecimal.test.ts.snap b/src/BigDecimal.test.ts.snap
index 8719ba4885b41ec273c07d37413c804b9da7932f..846b317f39597decae8eab1fdb7097893fce8f50 100644
GIT binary patch
literal 443
zcmV;s0Yv^mRzV<BZeeh9Xm4~Nb~6eC0At^~HC$9i_|5(a4yk+{fNqWRRmWUUGBbg?
zCrn`o7axlV00000000Bkl)XwrF%-xDrysV6(n=kQE&*pttDqn_D7rX1xTd|a2JcNS
zNs79u2yQ-rTYUl_!guf`d<aQz(+{ZNQfSX~^2<s1ofAm^x*hAzt$qFwPP$l_Q`tQe
z9hvZ$rQBGly3#71+8gcc>qiuE$FCmqD8UESDR&6q7(k738&o_uMw=R~gp?>`)oK;A
z4kA#+7jIG?RNSCaBCO?I5!O3ngCpj&W(ijhEDBCB?+7bm-WKuQAG<@#w|QE&CN0H%
zs+CYq@|Y>@xRY8jX?@OYFHN;^BFdcax9)^A(aa+Y?Y*tE@grV3ai-mkFl<T3?!kZT
zd-JrfPuhD+&QvdH3zJF4lV|~a99P+!PkCkkn;Rc(baaw(BQEv$hkNR0`adK6GL_E&
zTmVo2UI4rU_yq6;;Cs-P@8!f8{xIlekX0%b&?=||TJyai$k%pTjs50Sw1zcAp{U@C
l0?o~&`AIsup%7?pcf^W;Q8S>Gfbx5dgI|G$Tz>=x002$w%tHVG

literal 243
zcmV<P01W>@RzV<BZeeh9Xm4~Nb~6eC0ATg)MxFKe1o&T>)Mq4ZGkz;8mVRG!wuy9E
z|4x&)eIJVm00000000A9n3j~2pPXIXxG1$Gvm__A#3?h~B{exSH!(*qIX|}`u_!ep
zKeIS5v7k63zofWvVM<D3Nn*qsW(IZ!5MbnB<ZuDfUO=1&#4SKP3y3!W@ev@t4#dKY
zY=VrejzvX@m5huq7C%2f10xp$BRc~l4^RaYg9sxt10$;-qp+@_p0NQ6FoddMWP~YV
t0V#rsGGP^EMizyezycFx(uIq$!o(O2U_xv#A!Z{zGXTu3U~41+001y{SiArL

diff --git a/src/BigDecimal.ts b/src/BigDecimal.ts
index 42ef965..d761adf 100644
--- a/src/BigDecimal.ts
+++ b/src/BigDecimal.ts
@@ -93,10 +93,21 @@ export class BigDecimal {
     }
 
     // split into integer and decimal parts
-    const [integer, decimal] = str.split(".")
+    const [integer, decimal, ...rest] = str.split(".")
+    if (rest.length > 0) {
+      error("BigDecimal: too many decimal places")
+    }
 
     // The unscaled value is the integer part followed by the decimal part
-    this.#value = BigInt(`${integer}${decimal ?? ""}`)
+    try {
+      this.#value = BigInt(`${integer}${decimal ?? ""}`)
+    } catch (e) {
+      if (e instanceof Error && e.message.includes("Cannot convert")) {
+        error("BigDecimal: not a number")
+      }
+
+      throw e
+    }
     // The initial scale is either given (needed for certain math operations) or the length of the decimal part
     this.#scale = scale ?? decimal?.length ?? 0
 
diff --git a/src/collections.test.ts.snap b/src/collections.test.ts.snap
index d8a29a9ee20920d002deaf9155420d8c2bb8bec6..815ea5e8ef735edee4fdbe9aefcc78927cc68a19 100644
GIT binary patch
literal 644
zcmV-~0(<>IRzV<BZeeh9Xm4~Nb~6eC0O|*1>5g+Ym*Oe~8taAr?5$nP1KvQ_P$65H
zrr-Z=kROW(00000000B6R6UQ=KoEVic0Ncrk`M|`LdXJyf<!@*69u9<5EPLh6}mf7
ztsNgR_+n#kP6W|VA!-^b#K8}tK>QCXL`6*rc5KJl*bWD{uy%HycHet5J4gGv?HEt|
z*B?w_3EO;j&L2Bdd!%vScMOXQ^VUo=9M3ZiVb3go!d-vt2><2LXv78IeWRd);G-(3
z*8$uFum|7}K%2@fDi8I?rXh%uWwY4?ZGaR|18rhwf>o(SrLN`+FN{<oIoV4knVjsW
zl1eP)yewtM65}E<ud>8E05Cbe80zM5rC!WaPV}RMD%WD)vW4kw`?HBrM1LnmU%3V#
zkZ?DqUfT9NJ`0%7SB*vkR71e;WIzK8<HMLp_VaQ=$MeO|yFayUjZdPuh}g%xCVBA}
zO%mRg(<Jp2wH!z@1-WzJidmSbY{VkZ#v*Ml?s2zBmYtTh1>gpN0f2|=JXh9v9v3Cz
zohm}i?~&(B-NLuI$8Kl&J_Mluk?*I7rT~)u<l)x4^p+lOeNJx~Vf%gm{c3&y_$gVz
zmaM1}QwTUg%b=1BY7?+2fhrk|Tqn9nq2M~vfPlc+TKKOMJ)NhL_$@`=uulYhA;}YE
z*^?@<uLOLPVd@Hu7*Jsnth@rdz<`bntF9D6ZeZf+g8U;uUk5PczB}OVz_BJp??Ox3
zu7nny?sTtQ)jGZ4*PpNAGcQGF+I(rA1Yyzn@3Y!^7r^u5j}tYxEN4>J7QAv0jRhiW
emTWFOTRXh}-!NhFFj3`UQvL<t$1y(k2LJ%ib}xef

literal 642
zcmV-|0)72KRzV<BZeeh9Xm4~Nb~6eC0GD1ocR)3%2}guHaf297!8e+$SCgysw2eFc
zM9s{XJs*n*00000000B6R6UQ=KoH&WM-p-zPB;oqLdXJyf<!?QM1g1y1VtoBh3-yN
zYsbg=*t3njK^W0cA!-^b#K8}tK>QCXL`6->*s-0>#&$R$(s*ZQUe<5kj^}94V!r((
zdh^lYE@#g3bJ4y(WfPM|k#D<{JGW!g_QTMzIg8!MqX7bV^y+9bp`7l#RY{X1KWKq=
z1J_$<yJ*kQHlWdk#@IT*KLZqQr_&*@PCzAKAVxWpczPG~z8Uc_-Dv=Fav&rXIXM)P
zYF^5Dxs+{}@7ERcx~!OoXx{OQfqn&7800+V#4t-}@?Gq?j63006nl0Z{cVB1dJWg4
zgnK!4eJc!UoG_nxhG7tBlZ4;Nga(-lpY8!<Jueq@!ibN<2UEsO>Sg;nVxOv-<mF#9
zN&2>mCRr1xRX{od<nCd><22D+&x<^p7s)8UPlLL$m{`_zTyLU{&>pSQTwSGkekmDm
z;SzFwk3)YN)P9@0%AGRZ$7t3c>3#}eiol{jX&QPjhO9L7MGV<#`~ASsPqbf>6v~1W
zEl^Y-<OD2&bQ!dPfK3V1ENSF5fQyh8jNS;nMA>%w#K6;8s@T7SOdI7hdS5}(L|xPb
zVc!t)U505(Fl0iSiUeyc!7d=AC&OAx7a=z=Q1L?k5n!zX*mB<;(qQDfUfp+L7Hy}K
zE}ZW5uUs{IgXA%sdHI=_vNIW7m?z1$?)(pBZM}o`;`rl4OI}tnsoQg26$oRFD4Qjl
cbIn!`@BcSU6nU6v@-S)q2H?jrKK2Iy04vBYIRF3v


From f02f30f3aec887e829d65f69806bf6f84a5d0bbd Mon Sep 17 00:00:00 2001
From: Mischa Holz <me@mhlz.de>
Date: Fri, 26 Sep 2025 21:57:47 +0200
Subject: [PATCH 2/4] Update src/BigDecimal.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/BigDecimal.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/BigDecimal.ts b/src/BigDecimal.ts
index d761adf..c67451d 100644
--- a/src/BigDecimal.ts
+++ b/src/BigDecimal.ts
@@ -102,7 +102,7 @@ export class BigDecimal {
     try {
       this.#value = BigInt(`${integer}${decimal ?? ""}`)
     } catch (e) {
-      if (e instanceof Error && e.message.includes("Cannot convert")) {
+      if (e instanceof SyntaxError) {
         error("BigDecimal: not a number")
       }
 

From 2cb8fa3e581e6ec2b84a2d8664ad80b9381b2509 Mon Sep 17 00:00:00 2001
From: Mischa Holz <me@mhlz.de>
Date: Fri, 26 Sep 2025 22:07:59 +0200
Subject: [PATCH 3/4] Update src/BigDecimal.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/BigDecimal.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/BigDecimal.ts b/src/BigDecimal.ts
index c67451d..33c7f62 100644
--- a/src/BigDecimal.ts
+++ b/src/BigDecimal.ts
@@ -95,7 +95,7 @@ export class BigDecimal {
     // split into integer and decimal parts
     const [integer, decimal, ...rest] = str.split(".")
     if (rest.length > 0) {
-      error("BigDecimal: too many decimal places")
+      error("BigDecimal: multiple decimal points found")
     }
 
     // The unscaled value is the integer part followed by the decimal part

From 7637f16ee4386915d5847438d4cf881debbefb74 Mon Sep 17 00:00:00 2001
From: Mischa Holz <me@mhlz.de>
Date: Fri, 26 Sep 2025 22:09:10 +0200
Subject: [PATCH 4/4] Update snapshots

---
 src/BigDecimal.test.ts.md   |   2 +-
 src/BigDecimal.test.ts.snap | Bin 443 -> 454 bytes
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/BigDecimal.test.ts.md b/src/BigDecimal.test.ts.md
index 9825cb6..9f3754c 100644
--- a/src/BigDecimal.test.ts.md
+++ b/src/BigDecimal.test.ts.md
@@ -9,7 +9,7 @@ Generated by [AVA](https://avajs.dev).
 > too many decimal places
 
     Error {
-      message: 'BigDecimal: too many decimal places',
+      message: 'BigDecimal: multiple decimal points found',
     }
 
 > weird exponential notation
diff --git a/src/BigDecimal.test.ts.snap b/src/BigDecimal.test.ts.snap
index 846b317f39597decae8eab1fdb7097893fce8f50..a94aae41ab5de896d74f141b66101c7b27e63700 100644
GIT binary patch
literal 454
zcmV;%0XhCbRzV<BZeeh9Xm4~Nb~6eC0NZPTd>Y8di-oUQF-bO8S&9(<zX_-d=0idk
z`_HFeBp-_i00000000Bkl)p+tF%*Y?r?pl@X{8RLOI8O<tDqn_D7rX1xTd|a26K~3
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w(3o1yVTLG%mO?1f!c1D6q@x>_A}#EVSSd1UM6?`Hald}}3z`Pg!U_fe0P2&~RsaA1

literal 443
zcmV;s0Yv^mRzV<BZeeh9Xm4~Nb~6eC0At^~HC$9i_|5(a4yk+{fNqWRRmWUUGBbg?
zCrn`o7axlV00000000Bkl)XwrF%-xDrysV6(n=kQE&*pttDqn_D7rX1xTd|a2JcNS
zNs79u2yQ-rTYUl_!guf`d<aQz(+{ZNQfSX~^2<s1ofAm^x*hAzt$qFwPP$l_Q`tQe
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zTmVo2UI4rU_yq6;;Cs-P@8!f8{xIlekX0%b&?=||TJyai$k%pTjs50Sw1zcAp{U@C
l0?o~&`AIsup%7?pcf^W;Q8S>Gfbx5dgI|G$Tz>=x002$w%tHVG