fix: Blockscout and Etherscan lookups are off until the user turns them on (closes #668)

Out of the box the wallet sent the user's addresses to Blockscout and each recipient's address to Etherscan. Two settings, "Use Blockscout" and "Check recipients on Etherscan", now gate every request that sends the user's data to those services. Both start off and are offered unticked on Welcome and in Settings. Each request reads its setting from storage before it asks. An answer that lands after the setting went off is dropped. While a setting is off, the screens that rely on it say so. ENS lookups ask only the RPC endpoint, so a name resolved off-chain does not resolve.

RULES.md's External Communication item is now out of date. Its new wording will be proposed on #211 once this lands.

Model: opus-5-5 (implementation, summary); fable-5-1 (prose)

src/popup/views/helpers.js

@@ -21,7 +21,10 @@ const {
     truncateAmountNeverZero,
     isBelowOneMillionth,
 } = require("../../shared/amountDisplay");
-const { resolveTokenSymbol } = require("../../shared/approvalAmount");
+const {
+    resolveTokenDecimals,
+    resolveTokenSymbol,
+} = require("../../shared/approvalAmount");
 const { getProvider } = require("../../shared/balances");
 const { DEBUG } = require("../../shared/constants");
 const { escapeHtml } = require("../../shared/html");
@@ -306,10 +309,16 @@ function nativeCurrency() {
 // names a token on one network only, and every token balance held is the
 // active network's, so another network gets the tokens tracked on it
 // (state.networkTrackedTokens, see applyChainSwitchFields()) and no balances.
+//
+// The wallets' balances hold what Blockscout reported for each token. So the
+// wallets are returned only while "Use Blockscout" is on.
 function tokenSourcesByChainId(chainId) {
     const net = chainId ? networkByChainId(chainId) : currentNetwork();
     if (net && net.id === state.networkId) {
-        return { trackedTokens: state.trackedTokens, wallets: state.wallets };
+        return {
+            trackedTokens: state.trackedTokens,
+            wallets: state.useBlockscout ? state.wallets : [],
+        };
     }
     return {
         trackedTokens: (net && state.networkTrackedTokens[net.id]) || [],
@@ -317,11 +326,39 @@ function tokenSourcesByChainId(chainId) {
     };
 }
 
-// The symbol shown for a token line on the network with `chainId`, or on the
-// active network when none is given: from the bundled list, the tokens the
-// user tracks, and the explorer's report, the sources the amount line's scale
-// comes from. Null when no source names one, so the token lines keep saying
-// `Unknown token` for a token nothing knows.
+// The line shown under a token while "Use Blockscout" is off. The token gets
+// the line only when the bundled list and the tracked tokens lack its name or
+// decimals. Otherwise this returns "". The token is a contract address on the
+// network with `chainId`, or on the active network when none is given. "ETH"
+// and null are no contract, and get "". A token that is not text also gets "":
+// WaitTx and ErrorTx pass a token restored from storage unchecked.
+function blockscoutOffTokenNoteHtml(token, chainId) {
+    if (typeof token !== "string") return "";
+    if (state.useBlockscout || !token || token === "ETH") return "";
+    const sources = tokenSourcesByChainId(chainId);
+    if (
+        resolveTokenSymbol(token, sources) !== null &&
+        resolveTokenDecimals(token, sources) !== null
+    ) {
+        return "";
+    }
+    return (
+        '<div class="text-xs text-muted">Blockscout\'s report of your balances' +
+        ' is not used to name this token, because "Use Blockscout" is off in' +
+        " Settings.</div>"
+    );
+}
+
+// The symbol shown for a token line, from these sources in order:
+//
+// - the bundled list
+// - the tokens the user tracks
+// - the explorer's report, while "Use Blockscout" is on
+//
+// The network is the one with `chainId`, or the active network when none is
+// given. The amount line's scale comes from the same sources. Null when no
+// source names one, so the token lines keep saying `Unknown token` for a token
+// nothing knows.
 function tokenLabel(address, chainId) {
     return resolveTokenSymbol(address, tokenSourcesByChainId(chainId));
 }
@@ -534,6 +571,12 @@ function addressTitle(address, wallets) {
 const CONTRACT_CREATION_TEXT =
     "This transaction creates a new contract. It has no recipient.";
 
+// The line shown in place of the transaction history on Home, AddressDetail and
+// AddressToken while "Use Blockscout" is off. That history comes from
+// Blockscout alone.
+const HISTORY_OFF_TEXT =
+    'No transaction history is shown, because "Use Blockscout" is off in Settings.';
+
 // The last two lines of a transaction history row: the counterparty's colour
 // dot and name beside the amount, then its full address. A contract creation
 // the user sent has no counterparty (its `to` is ""), so its row has the
@@ -791,6 +834,7 @@ module.exports = {
     unknownableAmount,
     nativeCurrency,
     tokenSourcesByChainId,
+    blockscoutOffTokenNoteHtml,
     tokenLabel,
     formatFee,
     addressDotHtml,
@@ -799,6 +843,7 @@ module.exports = {
     displaySymbol,
     addressTitle,
     CONTRACT_CREATION_TEXT,
+    HISTORY_OFF_TEXT,
     txCounterpartyHtml,
     formatAddressHtml,
     renderAddressHtml,