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Avoid hashing CARGO_ variables that are redundant/unrelated #2495

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Avoid hashing CARGO_ variables that are redundant/unrelated #2495

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Avoid hashing CARGO_ variables that are redundant or don't affect res…
kornelski Nov 12, 2025
971b4e0
Merge branch 'main' into more-envs
sylvestre Dec 17, 2025
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23 changes: 14 additions & 9 deletions src/compiler/rust.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1518,15 +1518,19 @@ where
continue;
}

// CARGO_MAKEFLAGS will have jobserver info which is extremely non-cacheable.
// CARGO_REGISTRIES_*_TOKEN contains non-cacheable secrets.
// Registry override config doesn't need to be hashed, because deps' package IDs
// already uniquely identify the relevant registries.
// CARGO_BUILD_JOBS only affects Cargo's parallelism, not rustc output.
if var == "CARGO_MAKEFLAGS"
|| var.starts_with("CARGO_REGISTRIES_")
|| var == "CARGO_BUILD_JOBS"
{
let may_skip = var == "CARGO_MAKEFLAGS" // will have jobserver info which is extremely non-cacheable.
|| var == "CARGO_BUILD_JOBS" // does not affect results
|| var.starts_with("CARGO_REGISTRIES_") // CARGO_REGISTRIES_*_TOKEN contains non-cacheable secrets, and package IDs already uniquely identify the relevant registries.
|| var.starts_with("CARGO_REGISTRY_") // same as CARGO_REGISTRIES_*
|| var == "CARGO_TARGET_DIR" // already included in the file paths
|| var == "CARGO_BUILD_BUILD_DIR"
|| var == "CARGO_BUILD_TARGET_DIR"
|| var.starts_with("CARGO_HTTP_") // not relevant
|| var.starts_with("CARGO_NET_")
|| var.starts_with("CARGO_TERM_")
|| var.starts_with("CARGO_ALIAS_")
|| var == "CARGO_CACHE_AUTO_CLEAN_FREQUENCY";
if may_skip {
Comment on lines +1521 to +1533
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@sylvestre sylvestre Dec 17, 2025

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maybe something like:

Suggested change
let may_skip = var == "CARGO_MAKEFLAGS" // will have jobserver info which is extremely non-cacheable.
|| var == "CARGO_BUILD_JOBS" // does not affect results
|| var.starts_with("CARGO_REGISTRIES_") // CARGO_REGISTRIES_*_TOKEN contains non-cacheable secrets, and package IDs already uniquely identify the relevant registries.
|| var.starts_with("CARGO_REGISTRY_") // same as CARGO_REGISTRIES_*
|| var == "CARGO_TARGET_DIR" // already included in the file paths
|| var == "CARGO_BUILD_BUILD_DIR"
|| var == "CARGO_BUILD_TARGET_DIR"
|| var.starts_with("CARGO_HTTP_") // not relevant
|| var.starts_with("CARGO_NET_")
|| var.starts_with("CARGO_TERM_")
|| var.starts_with("CARGO_ALIAS_")
|| var == "CARGO_CACHE_AUTO_CLEAN_FREQUENCY";
if may_skip {
// Skip environment variables that shouldn't affect caching
const CARGO_SKIP_VARS: &[&str] = &[
"CARGO_MAKEFLAGS", // jobserver info which is extremely non-cacheable
"CARGO_BUILD_JOBS", // does not affect results
"CARGO_TARGET_DIR", // already included in the file paths
"CARGO_BUILD_BUILD_DIR",
"CARGO_BUILD_TARGET_DIR",
"CARGO_CACHE_AUTO_CLEAN_FREQUENCY",
];
const CARGO_SKIP_PREFIXES: &[&str] = &[
"CARGO_REGISTRIES_", // contains non-cacheable secrets, package IDs already identify registries
"CARGO_REGISTRY_", // same as CARGO_REGISTRIES_*
"CARGO_HTTP_", // not relevant
"CARGO_NET_",
"CARGO_TERM_",
"CARGO_ALIAS_",
];
let may_skip = CARGO_SKIP_VARS.contains(&var.as_str())
|| CARGO_SKIP_PREFIXES
.iter()
.any(|prefix| var.starts_with(prefix));
if may_skip {

continue;
}

Expand Down Expand Up @@ -3502,6 +3506,7 @@ proc_macro false
OsString::from("CARGO_BUILD_JOBS"),
OsString::from("ignored"),
),
(OsString::from("CARGO_TERM_COLOR"), OsString::from("never")),
]
.to_vec(),
false,
Expand Down