fix: make solidity --snapshot-check read-only

.changeset/quiet-melons-wave.md

@@ -0,0 +1,5 @@
+---
+"hardhat": patch
+---
+
+Make `hardhat test solidity --snapshot-check` read-only so it no longer rewrites or deletes `.gas-snapshot` or `snapshots/*.json` files; it now reports differences, fails when a stored gas value changed, and suggests `--snapshot` when there's no baseline.

packages/hardhat/src/internal/builtin-plugins/gas-analytics/function-gas-snapshots.ts

@@ -64,7 +64,7 @@ export interface FunctionGasSnapshotChange {
 export interface FunctionGasSnapshotCheckResult {
   passed: boolean;
   comparison: FunctionGasSnapshotComparison;
-  written: boolean;
+  noBaseline: boolean;
 }
 
 export function getFunctionGasSnapshotsPath(basePath: string): string {
@@ -323,16 +323,14 @@ export async function checkFunctionGasSnapshots(
     previousFunctionGasSnapshots = await readFunctionGasSnapshots(basePath);
   } catch (error) {
     if (error instanceof FileNotFoundError) {
-      await writeFunctionGasSnapshots(basePath, functionGasSnapshots);
-
       return {
         passed: true,
         comparison: {
           added: [],
           removed: [],
           changed: [],
         },
-        written: true,
+        noBaseline: functionGasSnapshots.length > 0,
       };
     }
 
@@ -344,67 +342,60 @@ export async function checkFunctionGasSnapshots(
     functionGasSnapshots,
   );
 
-  // Update snapshots when functions are added or removed (but not changed)
-  const hasAddedOrRemoved =
-    comparison.added.length > 0 || comparison.removed.length > 0;
-  if (comparison.changed.length === 0 && hasAddedOrRemoved) {
-    await writeFunctionGasSnapshots(basePath, functionGasSnapshots);
-  }
-
   return {
     passed: comparison.changed.length === 0,
     comparison,
-    written: hasAddedOrRemoved,
+    noBaseline: false,
   };
 }
 
 export function logFunctionGasSnapshotsSection(
   result: FunctionGasSnapshotCheckResult,
   logger: typeof console.log = console.log,
 ): void {
-  const { comparison, written } = result;
+  const { comparison, noBaseline } = result;
   const changedLength = comparison.changed.length;
   const addedLength = comparison.added.length;
   const removedLength = comparison.removed.length;
   const hasChanges = changedLength > 0;
   const hasAdded = addedLength > 0;
   const hasRemoved = removedLength > 0;
   const hasAnyDifferences = hasChanges || hasAdded || hasRemoved;
-  const isFirstTimeWrite = written && !hasAnyDifferences;
 
   // Nothing to report
-  if (!isFirstTimeWrite && !hasAnyDifferences) {
+  if (!noBaseline && !hasAnyDifferences) {
     return;
   }
 
-  logger(
-    formatSectionHeader("Function gas snapshots", {
-      changedLength,
-      addedLength,
-      removedLength,
-    }),
-  );
-
-  if (isFirstTimeWrite) {
-    logger();
+  if (noBaseline) {
     logger(
       styleText(
-        "green",
-        "  No existing snapshots found. Function gas snapshots written successfully",
+        "yellow",
+        "Function gas snapshots: no baseline found. Run your tests with --snapshot to create one.",
       ),
     );
     logger();
     return;
   }
 
+  logger(
+    formatSectionHeader("Function gas snapshots", {
+      changedLength,
+      addedLength,
+      removedLength,
+    }),
+  );
+
   if (hasChanges) {
     logger();
     printFunctionGasSnapshotChanges(comparison.changed, logger);
   }
 
   if (hasAdded) {
     logger();
-    logger(`  Added ${comparison.added.length} function(s):`);
+    logger(
+      `  ${comparison.added.length} function(s) produced by this run are not in the baseline:`,
+    );
     const addedLines = stringifyFunctionGasSnapshots(comparison.added).split(
       "\n",
     );
@@ -415,7 +406,9 @@ export function logFunctionGasSnapshotsSection(
 
   if (hasRemoved) {
     logger();
-    logger(`  Removed ${comparison.removed.length} function(s):`);
+    logger(
+      `  ${comparison.removed.length} stored function(s) were not produced by this run:`,
+    );
     const removedLines = stringifyFunctionGasSnapshots(
       comparison.removed,
     ).split("\n");

packages/hardhat/src/internal/builtin-plugins/gas-analytics/snapshot-cheatcodes.ts

@@ -78,7 +78,7 @@ export interface SnapshotCheatcodesComparison {
 export interface SnapshotCheatcodesCheckResult {
   passed: boolean;
   comparison: SnapshotCheatcodesComparison;
-  written: boolean;
+  noBaseline: boolean;
   renamedGroups: RenamedSnapshotGroup[];
 }
 
@@ -363,20 +363,14 @@ export async function checkSnapshotCheatcodes(
     previousSnapshotCheatcodes = await readSnapshotCheatcodes(basePath);
   } catch (error) {
     if (error instanceof FileNotFoundError) {
-      // Only write if there are cheatcodes to save
-      const written = snapshotCheatcodes.size > 0;
-      if (written) {
-        await writeSnapshotCheatcodes(basePath, snapshotCheatcodes);
-      }
-
       return {
         passed: true,
         comparison: {
           added: [],
           removed: [],
           changed: [],
         },
-        written,
+        noBaseline: snapshotCheatcodes.size > 0,
         renamedGroups,
       };
     }
@@ -389,17 +383,10 @@ export async function checkSnapshotCheatcodes(
     snapshotCheatcodes,
   );
 
-  // Update snapshots when functions are added or removed (but not changed)
-  const hasAddedOrRemoved =
-    comparison.added.length > 0 || comparison.removed.length > 0;
-  if (comparison.changed.length === 0 && hasAddedOrRemoved) {
-    await writeSnapshotCheatcodes(basePath, snapshotCheatcodes);
-  }
-
   return {
     passed: comparison.changed.length === 0,
     comparison,
-    written: hasAddedOrRemoved,
+    noBaseline: false,
     renamedGroups,
   };
 }
@@ -408,49 +395,49 @@ export function logSnapshotCheatcodesSection(
   result: SnapshotCheatcodesCheckResult,
   logger: typeof console.log = console.log,
 ): void {
-  const { comparison, written } = result;
+  const { comparison, noBaseline } = result;
   const changedLength = comparison.changed.length;
   const addedLength = comparison.added.length;
   const removedLength = comparison.removed.length;
   const hasChanges = changedLength > 0;
   const hasAdded = addedLength > 0;
   const hasRemoved = removedLength > 0;
   const hasAnyDifferences = hasChanges || hasAdded || hasRemoved;
-  const isFirstTimeWrite = written && !hasAnyDifferences;
 
   // Nothing to report
-  if (!isFirstTimeWrite && !hasAnyDifferences) {
+  if (!noBaseline && !hasAnyDifferences) {
     return;
   }
 
-  logger(
-    formatSectionHeader("Snapshot cheatcodes", {
-      changedLength,
-      addedLength,
-      removedLength,
-    }),
-  );
-
-  if (isFirstTimeWrite) {
-    logger();
+  if (noBaseline) {
     logger(
       styleText(
-        "green",
-        "  No existing snapshots found. Snapshot cheatcodes written successfully",
+        "yellow",
+        "Snapshot cheatcodes: no baseline found. Run your tests with --snapshot to create one.",
       ),
     );
     logger();
     return;
   }
 
+  logger(
+    formatSectionHeader("Snapshot cheatcodes", {
+      changedLength,
+      addedLength,
+      removedLength,
+    }),
+  );
+
   if (hasChanges) {
     logger();
     printSnapshotCheatcodeChanges(comparison.changed, logger);
   }
 
   if (hasAdded) {
     logger();
-    logger(`  Added ${comparison.added.length} snapshot(s):`);
+    logger(
+      `  ${comparison.added.length} snapshot(s) produced by this run are not in the baseline:`,
+    );
     const addedLines = stringifySnapshotCheatcodes(comparison.added).split(
       "\n",
     );
@@ -461,7 +448,9 @@ export function logSnapshotCheatcodesSection(
 
   if (hasRemoved) {
     logger();
-    logger(`  Removed ${comparison.removed.length} snapshot(s):`);
+    logger(
+      `  ${comparison.removed.length} stored snapshot(s) were not produced by this run:`,
+    );
     const removedLines = stringifySnapshotCheatcodes(comparison.removed).split(
       "\n",
     );

packages/hardhat/src/internal/builtin-plugins/gas-analytics/tasks/solidity-test/task-action.ts

@@ -149,12 +149,12 @@ export function logSnapshotCheckResult(
   );
 
   const functionGasHasOutput =
-    functionGasSnapshotsCheck.written ||
+    functionGasSnapshotsCheck.noBaseline ||
     functionGasSnapshotsCheck.comparison.changed.length > 0 ||
     functionGasSnapshotsCheck.comparison.added.length > 0 ||
     functionGasSnapshotsCheck.comparison.removed.length > 0;
   const snapshotCheatcodesHasOutput =
-    snapshotCheatcodesCheck.written ||
+    snapshotCheatcodesCheck.noBaseline ||
     snapshotCheatcodesCheck.comparison.changed.length > 0 ||
     snapshotCheatcodesCheck.comparison.added.length > 0 ||
     snapshotCheatcodesCheck.comparison.removed.length > 0;