fix: custom canisters with a read-only wasm no longer fail to build w…

…ith a permissions error (#4066)

Fixes: https://dfinity.atlassian.net/browse/SDK-1848

CHANGELOG.md

@@ -88,6 +88,8 @@ This affects the following commands:
 Canisters with Motoko's Enhanced Orthogonal Persistence feature require `wasm_memory_persistence = Keep` when they get installed.
 Previously, when `dfx` attempted to install canisters with EOP enabled to a playground it didn't set `wasm_memory_persistence` properly.
 
+### fix: custom canisters with a read-only wasm no longer fail to build with a permissions error
+
 ### chore: improve `dfx deploy` messages.
 
 If users run `dfx deploy` without enough cycles, show additional messages to indicate what to do next.

e2e/tests-dfx/build.bash

@@ -15,6 +15,20 @@ teardown() {
   standard_teardown
 }
 
+@test "build custom canister succeeds even if input wasm is read-only" {
+  install_asset custom_canister
+  install_asset wasm/identity
+  chmod u-w main.wasm
+
+  dfx_start
+  dfx canister create --all
+  assert_command dfx build custom
+
+  jq '.canisters.custom.shrink=true' dfx.json | sponge dfx.json
+  jq '.canisters.custom.gzip=false' dfx.json | sponge dfx.json
+  assert_command dfx build custom
+}
+
 @test "can build a custom canister with wasm and/or candid from a url" {
   install_asset wasm/identity
   mkdir -p www/wasm

src/dfx/src/lib/models/canister.rs

@@ -288,6 +288,7 @@ impl Canister {
         // If not modified and not set "gzip" explicitly, copy the wasm file directly so that hash match.
         if !modified && !info.get_gzip() {
             dfx_core::fs::copy(build_output_wasm_path, &wasm_path)?;
+            dfx_core::fs::set_permissions_readwrite(&wasm_path)?;
             return Ok(());
         }