lint: Add check that every Cargo patch has a matching replacement

We canonicalize git URLs when linting Cargo patches, because Cargo
treats `path/to/repo` and `path/to/repo.git` identically (and similarly
it strips a trailing slash), so we allow `.cargo/config.offline` and
`Cargo.toml` to mismatch in this way to minimise lints.

.github/workflows/lints.yml

@@ -21,6 +21,10 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
+      - name: Cargo patches
+        run: ./test/lint/lint-cargo-patches.sh
+        if: always()
+
       - name: Include guards
         run: ./test/lint/lint-include-guards.sh
         if: always()

test/lint/lint-cargo-patches.sh

@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2022 The Zcash developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or https://www.opensource.org/licenses/mit-license.php .
+#
+# Check that any patched Cargo dependencies are correctly configured.
+
+export LC_ALL=C
+
+REPOBASE="$(dirname $0)/../.."
+CARGO_TOML="$REPOBASE/Cargo.toml"
+CONFIG_FILE="$REPOBASE/.cargo/config.offline"
+
+CARGO_TOML_PATCH_PREFIX="[patch.crates-io]"
+let CARGO_TOML_PATCH_START=$(grep -Fn "$CARGO_TOML_PATCH_PREFIX" $CARGO_TOML | cut -d: -f1)+1
+
+REPLACE_LINE="replace-with = \"vendored-sources\""
+
+EXIT_CODE=0
+
+# Check that every patch specifies a revision.
+# TODO: Implement.
+
+# Check that every patch has a matching replacement.
+for PATCH in $(tail -n+$CARGO_TOML_PATCH_START $CARGO_TOML | sed 's/.*git = "\([^"]*\)", rev = "\([^"]*\)".*/\1#\2/' | sort | uniq)
+do
+    PATCH_GIT=$(echo $PATCH | sed 's/#.*//')
+    PATCH_REV=$(echo $PATCH | sed 's/.*#//')
+
+    # Canonicalize the git URL (matching how Cargo treats them, so we don't over-lint).
+    # https://github.com/rust-lang/cargo/blob/master/src/cargo/util/canonical_url.rs
+    CANONICAL_GIT=$(echo $PATCH_GIT | sed 's/\/$//' | sed 's/.git$//')
+    MAYBE_SUFFIX="\(.git\)\?/\?"
+
+    CONFIG_START=$(grep -n "^\[source\.\"$CANONICAL_GIT$MAYBE_SUFFIX\"\]$" $CONFIG_FILE | cut -d: -f1)
+    if [ -n "$CONFIG_START" ]; then
+        HAVE_GIT=$(tail -n+$CONFIG_START $CONFIG_FILE | head -n4 | grep "^git = \"$CANONICAL_GIT$MAYBE_SUFFIX\"$")
+        HAVE_REV=$(tail -n+$CONFIG_START $CONFIG_FILE | head -n4 | grep "^rev = \"$PATCH_REV\"$")
+        HAVE_REPLACE=$(tail -n+$CONFIG_START $CONFIG_FILE | head -n4 | grep "^$REPLACE_LINE$")
+    fi
+
+    if [ -z "$CONFIG_START" ] || [ -z "$HAVE_GIT" ] || [ -z "$HAVE_REV" ] || [ -z "$HAVE_REPLACE" ]; then
+        echo "Missing replacement in .cargo/config.offline:"
+        echo "  [source.\"$PATCH_GIT\"]"
+        echo "  git = \"$PATCH_GIT\""
+        echo "  rev = \"$PATCH_REV\""
+        echo "  $REPLACE_LINE"
+        echo
+        EXIT_CODE=1
+    fi
+
+    # Reset for the next iteration.
+    HAVE_GIT=
+    HAVE_REV=
+    HAVE_REPLACE=
+done
+
+# Check for unused replacements.
+# TODO: Implement.
+
+exit ${EXIT_CODE}