fix: show balances and fees below 0.000001 as nonzero on the send screens (closes #343)

The stored ETH and token balances and the send-confirm screen's fee were each
cut to six decimal places, and a token holding cut to zero was dropped, so a
value below 0.000001 read as zero. Balances are now stored exactly, whatever
decimals a token declares, and every nonzero token holding is kept; the balance
check reads a token balance to its first 18 places. The balance lists, the
send-screen token selector, the address total and the remove-address warning
leave out a holding below 0.000001 themselves, through isBelowOneMillionth().
The send and send-confirm screens' balances, reserve and insufficient-balance
messages go through truncateAmountNeverZero(). The send-confirm and approval
screens both render the fee through formatFee(), which prices the exact fee in
USD.

Model: opus-5-5

src/popup/views/helpers.js

@@ -12,6 +12,11 @@
 // escapeHtml lives in src/shared/html.js, where the escape and the
 // reasoning behind it are; it is re-exported below so views keep importing
 // it from here.
+const { formatEther } = require("ethers");
+const {
+    truncateAmountNeverZero,
+    isBelowOneMillionth,
+} = require("../../shared/amountDisplay");
 const { DEBUG } = require("../../shared/constants");
 const { escapeHtml } = require("../../shared/html");
 const { isDebug } = require("../../shared/log");
@@ -247,6 +252,19 @@ function unknownableAmount(balance) {
     return Number.isFinite(n) ? n : null;
 }
 
+// A network fee in wei as the confirmation and approval screens both show it:
+// the ETH figure through truncateAmountNeverZero(), then its USD value when the
+// ETH price is known. The USD value is of the exact fee, not of the truncated
+// figure.
+function formatFee(wei) {
+    const eth = formatEther(wei);
+    const ethPrice = getPrice("ETH");
+    const usd = ethPrice ? formatUsd(parseFloat(eth) * ethPrice) : "";
+    return (
+        truncateAmountNeverZero(eth) + " ETH" + (usd ? " (" + usd + ")" : "")
+    );
+}
+
 // One row of the balance list: symbol, quantity, fiat value.
 //
 // `symbol` is the ERC-20's own symbol() as the block explorer reported it,
@@ -292,6 +310,9 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
     );
     const seen = new Set();
     for (const t of addr.tokenBalances || []) {
+        // A holding below 0.000001 is not listed, tracked or not. A tracked
+        // token then gets the zero row below while showZero is on.
+        if (isBelowOneMillionth(t.balance)) continue;
         // A null balance is a holding of an unstatable amount, not a holding
         // of zero, so the show-zero setting has no say over it: hiding it
         // would be asserting the zero nobody established. Anything that does
@@ -322,14 +343,16 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
 }
 
 // Whether an address holds anything at all: ETH or any ERC-20 the wallet
-// knows about. Deliberately unrounded — the rendered lines round to four
-// decimals, so a dust balance displays as 0.0000 while still being real
-// money at a real address. Callers that warn about holdings must ask this,
-// not the rendered figure.
+// knows about, except a token holding below 0.000001, which the balance list
+// under the remove-address warning leaves out too. Deliberately unrounded —
+// the rendered lines round to four decimals, so a dust balance displays as
+// 0.0000 while still being real money at a real address. Callers that warn
+// about holdings must ask this, not the rendered figure.
 function addressHoldsFunds(addr) {
     if (!addr) return false;
     if (parseFloat(addr.balance || "0") > 0) return true;
     for (const t of addr.tokenBalances || []) {
+        if (isBelowOneMillionth(t.balance)) continue;
         // A null balance is a holding whose amount could not be stated —
         // balances.js drops a row of zero base units before the scale is
         // consulted, so a row that survived with no quantity is holding
@@ -614,6 +637,7 @@ module.exports = {
     balanceLinesForAddress,
     addressHoldsFunds,
     unknownableAmount,
+    formatFee,
     addressColor,
     addressDotHtml,
     escapeHtml,