Fix Docs.rs build problem.

Building the Docs.rs documentation failed due to
a version environmental variable not being set.
This commit addresses the problem by defaulting
to the minimum supported tpm2-tss version when
building for the Docs.rs build.

Signed-off-by: Jesper Brynolf <[email protected]>

Author: Superhepper

tss-esapi/build.rs

@@ -2,18 +2,26 @@
 // SPDX-License-Identifier: Apache-2.0
 use semver::{Version, VersionReq};
 
+const TPM2_TSS_MINIMUM_VERSION: Version = Version::new(4, 1, 3);
+
 fn main() {
     println!("cargo:rustc-check-cfg=cfg(hierarchy_is_esys_tr)");
     println!("cargo:rustc-check-cfg=cfg(has_tss_base_rc_values_28_to_51)");
     println!("cargo:rustc-check-cfg=cfg(has_tss_base_rc_values_52_to_53)");
     println!("cargo:rustc-check-cfg=cfg(has_tpmu_sensitive_create)");
     println!("cargo:rustc-check-cfg=cfg(has_esys_tr_get_tpm_handle)");
 
-    let tss_version_string = std::env::var("DEP_TSS2_ESYS_VERSION")
-        .expect("Failed to parse ENV variable DEP_TSS2_ESYS_VERSION as string");
-
-    let tss_version = Version::parse(&tss_version_string)
-        .expect("Failed to parse the DEP_TSS2_ESYS_VERSION variable as a semver version");
+    // If documentation for Docs.rs is being built then the version is set
+    // to the minimum supported tpm2-tss version.
+    let tss_version = if std::env::var("DOCS_RS").is_ok() {
+        TPM2_TSS_MINIMUM_VERSION
+    } else {
+        let tss_version_string = std::env::var("DEP_TSS2_ESYS_VERSION")
+            .expect("Failed to parse ENV variable DEP_TSS2_ESYS_VERSION as string");
+
+        Version::parse(&tss_version_string)
+            .expect("Failed to parse the DEP_TSS2_ESYS_VERSION variable as a semver version")
+    };
 
     let supported_tss_version =
         VersionReq::parse("<5.0.0, >=2.3.3").expect("Failed to parse supported TSS version");