Fix bootstrap_runtime_toolchain_type reference #215
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mbland
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Oct 28, 2025
Resolves the `_allowlist_function_transition` error under Bazel 6, since `rules_java` 7.10.0 adds it back in: - bazelbuild/rules_java#210: Make rules_java backwards compatible with Bazel 6.3.0 bazelbuild/rules_java@30ecf3f However, this version breaks `bootcamp_library` under Bazel 7, which currently uses `@bazel_tools//tools/jdk:toolchain_jdk_17`, with the following error: ```txt $ USE_BAZEL_VERSION=7.6.2 bazel build //... ERROR: external/rules_java_builtin/toolchains/BUILD:254:14: While resolving toolchains for target @@rules_java_builtin//toolchains:platformclasspath (096dcc8): No matching toolchains found for types @@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type. To debug, rerun with --toolchain_resolution_debug='@@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type' ``` The next commit fixes this error by replacing that toolchain dependency with `@rules_java//toolchains:toolchain_jdk_17` instead. This is another repo ordering problem related to the legacy `WORKSPACE` prefix from Bazel 7.6.2 instantiating `rules_java` 7.6.5 as `@rules_java_builtin`. - The legacy `WORKSPACE` prefix instantiates `rules_java_builtin` from `rules_java` 7.6.5, as explained in "Bump to Bazel 7.6.2". - Bazel creates a repo mapping from `@rules_java` to `@rules_java_builtin` for `@bazel_tools` in its legacy `WORKSPACE` prefix. https://github.com/bazelbuild/bazel/blob/7.6.2/src/main/java/com/google/devtools/build/lib/bazel/rules/GenericRules.java#L56-L57 https://github.com/bazelbuild/bazel/blob/7.6.2/src/main/java/com/google/devtools/build/lib/bazel/rules/tools.WORKSPACE#L1-L5 - The legacy `bootcamp/WORKSPACE` file instantiates `rules_java` 7.10.0. `rules_java_dependencies` instantiates its JDK toolchain repos using an updated `toolchain_type`, and `rules_java_toolchains` registers them. - The legacy `WORKSPACE` suffix invokes the `rules_java_dependencies` macro from `rules_java` 7.6.5. This does nothing, because `rules_java` wraps the remote JDK toolchain repo rules in a `maybe`, and repos of the same names already exist. - The `@bazel_tools//tools/jdk` toolchains transitively depend upon `@rules_java_builtin//toolchains:platformclasspath` from `rules_java` 7.6.5. That target depends upon JDK toolchain repos using the previous type, `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. - No toolchains of that type exist, producing the error. These problems don't appear under Bzlmod, which never needed the `@rules_java_builtin` mechanism. This is because legacy `WORKSPACE` evaluation executes statements sequentially, while Bzlmod builds the module dependency graph _before_ instantiating repositories (within module extensions). In fact, `bazel {build,test} --enable_bzlmod //...` actually works at this point, though the migration hasn't really begun. --- This error happens because `rules_java` up to 7.9.1 contained the following definition in `toolchains/default_java_toolchain.bzl`: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type") ``` and `rules_java` 7.10.0 changed it to: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("//toolchains:bootstrap_runtime_toolchain_type") ``` - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/default_java_toolchain.bzl#L211 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L211 The generated toolchain configuration repos use this same `toolchain_type`, which `rules_java_toolchains()` registers: - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/remote_java_repository.bzl#L92 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/remote_java_repository.bzl#L92 As noted earlier, bazelbuild/rules_java#210 reinstated `_allowlist_function_transition`, required by Bazel 6. However, it also included this `toolchain_type` change. (`rules_java` 7.11.0 later touched up this change for local JDK toolchain repos in:) - bazelbuild/rules_java#215: Fix bootstrap_runtime_toolchain_type reference bazelbuild/rules_java@bcc5062 This affects all toolchains defined using the `default_java_toolchain` macro, which depend upon `@rules_java//toolchains:platformclasspath`. This target, defined by the `bootclasspath` rule, depends upon `_JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE`. - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L141 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L99 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L90 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L254-L258 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L304 The `rules_java` setup macro `rules_java_dependencies` depends upon `_remote_jdk_repos_for_version`. This macro wraps each remote toolchain repo instantiation in a `maybe`: - https://github.com/bazelbuild/rules_java/blob/7.6.5/java/repositories.bzl#L331-L341 The `rules_java` setup macros in the legacy `bootcamp/WORKSPACE` file instantiate the 7.10.0 toolchain repos first. This means that nothing happens when the the legacy `WORKSPACE` suffix invokes the 7.6.5 macros. This also means that all the remote JDK toolchain repos have the `toolchain_type` from 7.10.0, not from 7.6.5. `@bazel_tools//tools/jdk:toolchain_jdk_17` is an `alias` to `@rules_java//toolchains:toolchain_jdk_17`. However, Bazel maps this to the `@rules_java_builtin` repo, which is `rules_java` 7.6.5. - https://github.com/bazelbuild/bazel/blob/7.6.2/tools/jdk/BUILD.tools#L177-L178 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L271-L281 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L271-L281 As a result, that toolchain depends upon the `rules_java` 7.6.5 target, `@rules_java_builtin//toolchains:platformclasspath`. That target depends `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. Since no existing toolchains have that `toolchain_type`, the build fails. -- `rules_java` 7.12.2 and 8.6.0 actually restored the previous `toolchain_type`; upgrading to either of those versions would also fix this build: - bazelbuild/rules_java#246: bazelbuild/rules_java@b64eb7d bazelbuild/rules_java@4206c53 --- `@bazel_tools/tools/jdk:current_java_toolchain` remains intact. It's an `alias` to `@rules_java//toolchains:current_java_toolchain`, which is a `java_toolchain_alias`. Its `toolchains` attribute contains a direct dependency on `@bazel_tools//tools/jdk:toolchain_type`, which remains the same in `rules_java` 7.10.0. - https://github.com/bazelbuild/bazel/blob/7.6.2/tools/jdk/BUILD.tools#L155 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L79 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/java_toolchain_alias.bzl#L104 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/java_toolchain_alias.bzl#L107 --- The "Bump to rules_java 7.9.0 for Bazel 7 compatibility" section of the following commit message describes my first investigation into this phenomenon. It was very close, but not exactly correct, and not as complete as the description above. - bazel-contrib/rules_scala@cd22d88 This has broken other projects in the same way: - bazelbuild/bazel: [Bazel CI] Downstream project broken by rules_java upgrade #23619 bazelbuild/bazel#23619 Bazel 8.0.0 ships with `rules_java` 8.6.1, removed `@rules_java_builtin` from the legacy `WORKSPACE` prefix, and added `@rules_java` to the suffix. - https://github.com/bazelbuild/bazel/blob/8.0.0/MODULE.bazel#L28 - bazelbuild/bazel: Remove rules_java_builtin in WORKSPACE prefix bazelbuild/bazel@7506690
mbland
added a commit
to EngFlow-Academy/bzlmod-bootcamp
that referenced
this pull request
Oct 31, 2025
Resolves the `_allowlist_function_transition` error under Bazel 6, since `rules_java` 7.10.0 adds it back in: - bazelbuild/rules_java#210: Make rules_java backwards compatible with Bazel 6.3.0 bazelbuild/rules_java@30ecf3f However, this version breaks `bootcamp_library` under Bazel 7, which currently uses `@bazel_tools//tools/jdk:toolchain_jdk_17`, with the following error: ```txt $ USE_BAZEL_VERSION=7.6.2 bazel build //... ERROR: external/rules_java_builtin/toolchains/BUILD:254:14: While resolving toolchains for target @@rules_java_builtin//toolchains:platformclasspath (096dcc8): No matching toolchains found for types @@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type. To debug, rerun with --toolchain_resolution_debug='@@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type' ``` The next commit fixes this error by replacing that toolchain dependency with `@rules_java//toolchains:toolchain_jdk_17` instead. This is another repo ordering problem related to the legacy `WORKSPACE` prefix from Bazel 7.6.2 instantiating `rules_java` 7.6.5 as `@rules_java_builtin`. - The legacy `WORKSPACE` prefix instantiates `rules_java_builtin` from `rules_java` 7.6.5, as explained in "Bump to Bazel 7.6.2". - Bazel creates a repo mapping from `@rules_java` to `@rules_java_builtin` for `@bazel_tools` in its legacy `WORKSPACE` prefix. https://github.com/bazelbuild/bazel/blob/7.6.2/src/main/java/com/google/devtools/build/lib/bazel/rules/GenericRules.java#L56-L57 https://github.com/bazelbuild/bazel/blob/7.6.2/src/main/java/com/google/devtools/build/lib/bazel/rules/tools.WORKSPACE#L1-L5 - The legacy `bootcamp/WORKSPACE` file instantiates `rules_java` 7.10.0. `rules_java_dependencies` instantiates its JDK toolchain repos using an updated `toolchain_type`, and `rules_java_toolchains` registers them. - The legacy `WORKSPACE` suffix invokes the `rules_java_dependencies` macro from `rules_java` 7.6.5. This does nothing, because `rules_java` wraps the remote JDK toolchain repo rules in a `maybe`, and repos of the same names already exist. - The `@bazel_tools//tools/jdk` toolchains transitively depend upon `@rules_java_builtin//toolchains:platformclasspath` from `rules_java` 7.6.5. That target depends upon JDK toolchain repos using the previous type, `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. - No toolchains of that type exist, producing the error. These problems don't appear under Bzlmod, which never needed the `@rules_java_builtin` mechanism. This is because legacy `WORKSPACE` evaluation executes statements sequentially, while Bzlmod builds the module dependency graph _before_ instantiating repositories (within module extensions). In fact, `bazel {build,test} --enable_bzlmod //...` actually works at this point, though the migration hasn't really begun. --- This error happens because `rules_java` up to 7.9.1 contained the following definition in `toolchains/default_java_toolchain.bzl`: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type") ``` and `rules_java` 7.10.0 changed it to: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("//toolchains:bootstrap_runtime_toolchain_type") ``` - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/default_java_toolchain.bzl#L211 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L211 The generated toolchain configuration repos use this same `toolchain_type`, which `rules_java_toolchains()` registers: - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/remote_java_repository.bzl#L92 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/remote_java_repository.bzl#L92 As noted earlier, bazelbuild/rules_java#210 reinstated `_allowlist_function_transition`, required by Bazel 6. However, it also included this `toolchain_type` change. (`rules_java` 7.11.0 later touched up this change for local JDK toolchain repos in:) - bazelbuild/rules_java#215: Fix bootstrap_runtime_toolchain_type reference bazelbuild/rules_java@bcc5062 This affects all toolchains defined using the `default_java_toolchain` macro, which depend upon `@rules_java//toolchains:platformclasspath`. This target, defined by the `bootclasspath` rule, depends upon `_JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE`. - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L141 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L99 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L90 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L254-L258 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L304 The `rules_java` setup macro `rules_java_dependencies` depends upon `_remote_jdk_repos_for_version`. This macro wraps each remote toolchain repo instantiation in a `maybe`: - https://github.com/bazelbuild/rules_java/blob/7.6.5/java/repositories.bzl#L331-L341 The `rules_java` setup macros in the legacy `bootcamp/WORKSPACE` file instantiate the 7.10.0 toolchain repos first. This means that nothing happens when the the legacy `WORKSPACE` suffix invokes the 7.6.5 macros. This also means that all the remote JDK toolchain repos have the `toolchain_type` from 7.10.0, not from 7.6.5. `@bazel_tools//tools/jdk:toolchain_jdk_17` is an `alias` to `@rules_java//toolchains:toolchain_jdk_17`. However, Bazel maps this to the `@rules_java_builtin` repo, which is `rules_java` 7.6.5. - https://github.com/bazelbuild/bazel/blob/7.6.2/tools/jdk/BUILD.tools#L177-L178 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L271-L281 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L271-L281 As a result, that toolchain depends upon the `rules_java` 7.6.5 target, `@rules_java_builtin//toolchains:platformclasspath`. That target depends `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. Since no existing toolchains have that `toolchain_type`, the build fails. -- `rules_java` 7.12.2 and 8.6.0 actually restored the previous `toolchain_type`; upgrading to either of those versions would also fix this build: - bazelbuild/rules_java#246: bazelbuild/rules_java@b64eb7d bazelbuild/rules_java@4206c53 --- `@bazel_tools/tools/jdk:current_java_toolchain` remains intact. It's an `alias` to `@rules_java//toolchains:current_java_toolchain`, which is a `java_toolchain_alias`. Its `toolchains` attribute contains a direct dependency on `@bazel_tools//tools/jdk:toolchain_type`, which remains the same in `rules_java` 7.10.0. - https://github.com/bazelbuild/bazel/blob/7.6.2/tools/jdk/BUILD.tools#L155 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L79 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/java_toolchain_alias.bzl#L104 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/java_toolchain_alias.bzl#L107 --- The "Bump to rules_java 7.9.0 for Bazel 7 compatibility" section of the following commit message describes my first investigation into this phenomenon. It was very close, but not exactly correct, and not as complete as the description above. - bazel-contrib/rules_scala@cd22d88 This has broken other projects in the same way: - bazelbuild/bazel: [Bazel CI] Downstream project broken by rules_java upgrade #23619 bazelbuild/bazel#23619 Bazel 8.0.0 ships with `rules_java` 8.6.1, removed `@rules_java_builtin` from the legacy `WORKSPACE` prefix, and added `@rules_java` to the suffix. - https://github.com/bazelbuild/bazel/blob/8.0.0/MODULE.bazel#L28 - bazelbuild/bazel: Remove rules_java_builtin in WORKSPACE prefix bazelbuild/bazel@7506690
mbland
added a commit
to EngFlow-Academy/bzlmod-bootcamp
that referenced
this pull request
Nov 5, 2025
Resolves the `_allowlist_function_transition` error under Bazel 6, since `rules_java` 7.10.0 adds it back in: - bazelbuild/rules_java#210: Make rules_java backwards compatible with Bazel 6.3.0 bazelbuild/rules_java@30ecf3f However, this version breaks `bootcamp_library` under Bazel 7, which currently uses `@bazel_tools//tools/jdk:toolchain_jdk_17`, with the following error: ```txt $ USE_BAZEL_VERSION=7.7.0 bazel build //... ERROR: external/rules_java_builtin/toolchains/BUILD:254:14: While resolving toolchains for target @@rules_java_builtin//toolchains:platformclasspath (096dcc8): No matching toolchains found for types @@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type. To debug, rerun with --toolchain_resolution_debug='@@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type' ``` The next commit fixes this error by replacing that toolchain dependency with `@rules_java//toolchains:toolchain_jdk_17` instead. This is another repo ordering problem related to the legacy `WORKSPACE` prefix from Bazel 7.7.0 instantiating `rules_java` 7.6.5 as `@rules_java_builtin`. - The legacy `WORKSPACE` prefix instantiates `rules_java_builtin` from `rules_java` 7.6.5, as explained in "Bump to Bazel 7.7.0". - Bazel creates a repo mapping from `@rules_java` to `@rules_java_builtin` for `@bazel_tools` in its legacy `WORKSPACE` prefix. https://github.com/bazelbuild/bazel/blob/7.7.0/src/main/java/com/google/devtools/build/lib/bazel/rules/GenericRules.java#L56-L57 https://github.com/bazelbuild/bazel/blob/7.7.0/src/main/java/com/google/devtools/build/lib/bazel/rules/tools.WORKSPACE#L1-L5 - The legacy `bootcamp/WORKSPACE` file instantiates `rules_java` 7.10.0. `rules_java_dependencies` instantiates its JDK toolchain repos using an updated `toolchain_type`, and `rules_java_toolchains` registers them. - The legacy `WORKSPACE` suffix invokes the `rules_java_dependencies` macro from `rules_java` 7.6.5. This does nothing, because `rules_java` wraps the remote JDK toolchain repo rules in a `maybe`, and repos of the same names already exist. - The `@bazel_tools//tools/jdk` toolchains transitively depend upon `@rules_java_builtin//toolchains:platformclasspath` from `rules_java` 7.6.5. That target depends upon JDK toolchain repos using the previous type, `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. - No toolchains of that type exist, producing the error. These problems don't appear under Bzlmod, which never needed the `@rules_java_builtin` mechanism. This is because legacy `WORKSPACE` evaluation executes statements sequentially, while Bzlmod builds the module dependency graph _before_ instantiating repositories (within module extensions). In fact, `bazel {build,test} --enable_bzlmod //...` actually works at this point, though the migration hasn't really begun. --- This error happens because `rules_java` up to 7.9.1 contained the following definition in `toolchains/default_java_toolchain.bzl`: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type") ``` and `rules_java` 7.10.0 changed it to: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("//toolchains:bootstrap_runtime_toolchain_type") ``` - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/default_java_toolchain.bzl#L211 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L211 The generated toolchain configuration repos use this same `toolchain_type`, which `rules_java_toolchains()` registers: - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/remote_java_repository.bzl#L92 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/remote_java_repository.bzl#L92 As noted earlier, bazelbuild/rules_java#210 reinstated `_allowlist_function_transition`, required by Bazel 6. However, it also included this `toolchain_type` change. (`rules_java` 7.11.0 later touched up this change for local JDK toolchain repos in:) - bazelbuild/rules_java#215: Fix bootstrap_runtime_toolchain_type reference bazelbuild/rules_java@bcc5062 This affects all toolchains defined using the `default_java_toolchain` macro, which depend upon `@rules_java//toolchains:platformclasspath`. This target, defined by the `bootclasspath` rule, depends upon `_JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE`. - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L141 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L99 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L90 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L254-L258 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L304 The `rules_java` setup macro `rules_java_dependencies` depends upon `_remote_jdk_repos_for_version`. This macro wraps each remote toolchain repo instantiation in a `maybe`: - https://github.com/bazelbuild/rules_java/blob/7.6.5/java/repositories.bzl#L331-L341 The `rules_java` setup macros in the legacy `bootcamp/WORKSPACE` file instantiate the 7.10.0 toolchain repos first. This means that nothing happens when the the legacy `WORKSPACE` suffix invokes the 7.6.5 macros. This also means that all the remote JDK toolchain repos have the `toolchain_type` from 7.10.0, not from 7.6.5. `@bazel_tools//tools/jdk:toolchain_jdk_17` is an `alias` to `@rules_java//toolchains:toolchain_jdk_17`. However, Bazel maps this to the `@rules_java_builtin` repo, which is `rules_java` 7.6.5. - https://github.com/bazelbuild/bazel/blob/7.7.0/tools/jdk/BUILD.tools#L177-L178 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L271-L281 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L271-L281 As a result, that toolchain depends upon the `rules_java` 7.6.5 target, `@rules_java_builtin//toolchains:platformclasspath`. That target depends `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. Since no existing toolchains have that `toolchain_type`, the build fails. -- `rules_java` 7.12.2 and 8.6.0 actually restored the previous `toolchain_type`; upgrading to either of those versions would also fix this build: - bazelbuild/rules_java#246: bazelbuild/rules_java@b64eb7d bazelbuild/rules_java@4206c53 --- `@bazel_tools/tools/jdk:current_java_toolchain` remains intact. It's an `alias` to `@rules_java//toolchains:current_java_toolchain`, which is a `java_toolchain_alias`. Its `toolchains` attribute contains a direct dependency on `@bazel_tools//tools/jdk:toolchain_type`, which remains the same in `rules_java` 7.10.0. - https://github.com/bazelbuild/bazel/blob/7.7.0/tools/jdk/BUILD.tools#L155 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L79 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/java_toolchain_alias.bzl#L104 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/java_toolchain_alias.bzl#L107 --- The "Bump to rules_java 7.9.0 for Bazel 7 compatibility" section of the following commit message describes my first investigation into this phenomenon. It was very close, but not exactly correct, and not as complete as the description above. - bazel-contrib/rules_scala@cd22d88 This has broken other projects in the same way: - bazelbuild/bazel: [Bazel CI] Downstream project broken by rules_java upgrade #23619 bazelbuild/bazel#23619 Bazel 8.0.0 ships with `rules_java` 8.6.1, removed `@rules_java_builtin` from the legacy `WORKSPACE` prefix, and added `@rules_java` to the suffix. - https://github.com/bazelbuild/bazel/blob/8.0.0/MODULE.bazel#L28 - bazelbuild/bazel: Remove rules_java_builtin in WORKSPACE prefix bazelbuild/bazel@7506690
mbland
added a commit
to EngFlow-Academy/bzlmod-bootcamp
that referenced
this pull request
Nov 7, 2025
Resolves the `_allowlist_function_transition` error under Bazel 6, since `rules_java` 7.10.0 adds it back in: - bazelbuild/rules_java#210: Make rules_java backwards compatible with Bazel 6.3.0 bazelbuild/rules_java@30ecf3f However, this version breaks `bootcamp_library` under Bazel 7, which currently uses `@bazel_tools//tools/jdk:toolchain_jdk_17`, with the following error: ```txt $ USE_BAZEL_VERSION=7.7.0 bazel build //... ERROR: external/rules_java_builtin/toolchains/BUILD:254:14: While resolving toolchains for target @@rules_java_builtin//toolchains:platformclasspath (096dcc8): No matching toolchains found for types @@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type. To debug, rerun with --toolchain_resolution_debug='@@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type' ``` The next commit fixes this error by replacing that toolchain dependency with `@rules_java//toolchains:toolchain_jdk_17` instead. This is another repo ordering problem related to the legacy `WORKSPACE` prefix from Bazel 7.7.0 instantiating `rules_java` 7.6.5 as `@rules_java_builtin`. - The legacy `WORKSPACE` prefix instantiates `rules_java_builtin` from `rules_java` 7.6.5, as explained in "Bump to Bazel 7.7.0". - Bazel creates a repo mapping from `@rules_java` to `@rules_java_builtin` for `@bazel_tools` in its legacy `WORKSPACE` prefix. https://github.com/bazelbuild/bazel/blob/7.7.0/src/main/java/com/google/devtools/build/lib/bazel/rules/GenericRules.java#L56-L57 https://github.com/bazelbuild/bazel/blob/7.7.0/src/main/java/com/google/devtools/build/lib/bazel/rules/tools.WORKSPACE#L1-L5 - The legacy `bootcamp/WORKSPACE` file instantiates `rules_java` 7.10.0. `rules_java_dependencies` instantiates its JDK toolchain repos using an updated `toolchain_type`, and `rules_java_toolchains` registers them. - The legacy `WORKSPACE` suffix invokes the `rules_java_dependencies` macro from `rules_java` 7.6.5. This does nothing, because `rules_java` wraps the remote JDK toolchain repo rules in a `maybe`, and repos of the same names already exist. - The `@bazel_tools//tools/jdk` toolchains transitively depend upon `@rules_java_builtin//toolchains:platformclasspath` from `rules_java` 7.6.5. That target depends upon JDK toolchain repos using the previous type, `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. - No toolchains of that type exist, producing the error. These problems don't appear under Bzlmod, which never needed the `@rules_java_builtin` mechanism. This is because legacy `WORKSPACE` evaluation executes statements sequentially, while Bzlmod builds the module dependency graph _before_ instantiating repositories (within module extensions). In fact, `bazel {build,test} --enable_bzlmod //...` actually works at this point, though the migration hasn't really begun. --- This error happens because `rules_java` up to 7.9.1 contained the following definition in `toolchains/default_java_toolchain.bzl`: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type") ``` and `rules_java` 7.10.0 changed it to: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("//toolchains:bootstrap_runtime_toolchain_type") ``` - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/default_java_toolchain.bzl#L211 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L211 The generated toolchain configuration repos use this same `toolchain_type`, which `rules_java_toolchains()` registers: - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/remote_java_repository.bzl#L92 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/remote_java_repository.bzl#L92 As noted earlier, bazelbuild/rules_java#210 reinstated `_allowlist_function_transition`, required by Bazel 6. However, it also included this `toolchain_type` change. (`rules_java` 7.11.0 later touched up this change for local JDK toolchain repos in:) - bazelbuild/rules_java#215: Fix bootstrap_runtime_toolchain_type reference bazelbuild/rules_java@bcc5062 This affects all toolchains defined using the `default_java_toolchain` macro, which depend upon `@rules_java//toolchains:platformclasspath`. This target, defined by the `bootclasspath` rule, depends upon `_JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE`. - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L141 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L99 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L90 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L254-L258 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L304 The `rules_java` setup macro `rules_java_dependencies` depends upon `_remote_jdk_repos_for_version`. This macro wraps each remote toolchain repo instantiation in a `maybe`: - https://github.com/bazelbuild/rules_java/blob/7.6.5/java/repositories.bzl#L331-L341 The `rules_java` setup macros in the legacy `bootcamp/WORKSPACE` file instantiate the 7.10.0 toolchain repos first. This means that nothing happens when the the legacy `WORKSPACE` suffix invokes the 7.6.5 macros. This also means that all the remote JDK toolchain repos have the `toolchain_type` from 7.10.0, not from 7.6.5. `@bazel_tools//tools/jdk:toolchain_jdk_17` is an `alias` to `@rules_java//toolchains:toolchain_jdk_17`. However, Bazel maps this to the `@rules_java_builtin` repo, which is `rules_java` 7.6.5. - https://github.com/bazelbuild/bazel/blob/7.7.0/tools/jdk/BUILD.tools#L177-L178 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L271-L281 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L271-L281 As a result, that toolchain depends upon the `rules_java` 7.6.5 target, `@rules_java_builtin//toolchains:platformclasspath`. That target depends `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. Since no existing toolchains have that `toolchain_type`, the build fails. -- `rules_java` 7.12.2 and 8.6.0 actually restored the previous `toolchain_type`; upgrading to either of those versions would also fix this build: - bazelbuild/rules_java#246: bazelbuild/rules_java@b64eb7d bazelbuild/rules_java@4206c53 --- `@bazel_tools/tools/jdk:current_java_toolchain` remains intact. It's an `alias` to `@rules_java//toolchains:current_java_toolchain`, which is a `java_toolchain_alias`. Its `toolchains` attribute contains a direct dependency on `@bazel_tools//tools/jdk:toolchain_type`, which remains the same in `rules_java` 7.10.0. - https://github.com/bazelbuild/bazel/blob/7.7.0/tools/jdk/BUILD.tools#L155 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L79 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/java_toolchain_alias.bzl#L104 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/java_toolchain_alias.bzl#L107 --- The "Bump to rules_java 7.9.0 for Bazel 7 compatibility" section of the following commit message describes my first investigation into this phenomenon. It was very close, but not exactly correct, and not as complete as the description above. - bazel-contrib/rules_scala@cd22d88 This has broken other projects in the same way: - bazelbuild/bazel: [Bazel CI] Downstream project broken by rules_java upgrade #23619 bazelbuild/bazel#23619 Bazel 8.0.0 ships with `rules_java` 8.6.1, removed `@rules_java_builtin` from the legacy `WORKSPACE` prefix, and added `@rules_java` to the suffix. - https://github.com/bazelbuild/bazel/blob/8.0.0/MODULE.bazel#L28 - bazelbuild/bazel: Remove rules_java_builtin in WORKSPACE prefix bazelbuild/bazel@7506690
mbland
added a commit
to EngFlow-Academy/bzlmod-bootcamp
that referenced
this pull request
Nov 7, 2025
Resolves the `_allowlist_function_transition` error under Bazel 6, since `rules_java` 7.10.0 adds it back in: - bazelbuild/rules_java#210: Make rules_java backwards compatible with Bazel 6.3.0 bazelbuild/rules_java@30ecf3f However, this version breaks `bootcamp_library` under Bazel 7, which currently uses `@bazel_tools//tools/jdk:toolchain_jdk_17`, with the following error: ```txt $ USE_BAZEL_VERSION=7.7.0 bazel build //... ERROR: external/rules_java_builtin/toolchains/BUILD:254:14: While resolving toolchains for target @@rules_java_builtin//toolchains:platformclasspath (096dcc8): No matching toolchains found for types @@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type. To debug, rerun with --toolchain_resolution_debug='@@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type' ``` The next commit fixes this error by replacing that toolchain dependency with `@rules_java//toolchains:toolchain_jdk_17` instead. This is another repo ordering problem related to the legacy `WORKSPACE` prefix from Bazel 7.7.0 instantiating `rules_java` 7.6.5 as `@rules_java_builtin`. - The legacy `WORKSPACE` prefix instantiates `rules_java_builtin` from `rules_java` 7.6.5, as explained in "Bump to Bazel 7.7.0". - Bazel creates a repo mapping from `@rules_java` to `@rules_java_builtin` for `@bazel_tools` in its legacy `WORKSPACE` prefix. https://github.com/bazelbuild/bazel/blob/7.7.0/src/main/java/com/google/devtools/build/lib/bazel/rules/GenericRules.java#L56-L57 https://github.com/bazelbuild/bazel/blob/7.7.0/src/main/java/com/google/devtools/build/lib/bazel/rules/tools.WORKSPACE#L1-L5 - The legacy `bootcamp/WORKSPACE` file instantiates `rules_java` 7.10.0. `rules_java_dependencies` instantiates its JDK toolchain repos using an updated `toolchain_type`, and `rules_java_toolchains` registers them. - The legacy `WORKSPACE` suffix invokes the `rules_java_dependencies` macro from `rules_java` 7.6.5. This does nothing, because `rules_java` wraps the remote JDK toolchain repo rules in a `maybe`, and repos of the same names already exist. - The `@bazel_tools//tools/jdk` toolchains transitively depend upon `@rules_java_builtin//toolchains:platformclasspath` from `rules_java` 7.6.5. That target depends upon JDK toolchain repos using the previous type, `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. - No toolchains of that type exist, producing the error. These problems don't appear under Bzlmod, which never needed the `@rules_java_builtin` mechanism. This is because legacy `WORKSPACE` evaluation executes statements sequentially, while Bzlmod builds the module dependency graph _before_ instantiating repositories (within module extensions). In fact, `bazel {build,test} --enable_bzlmod //...` actually works at this point, though the migration hasn't really begun. --- This error happens because `rules_java` up to 7.9.1 contained the following definition in `toolchains/default_java_toolchain.bzl`: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type") ``` and `rules_java` 7.10.0 changed it to: ```python _JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE = Label("//toolchains:bootstrap_runtime_toolchain_type") ``` - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/default_java_toolchain.bzl#L211 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L211 The generated toolchain configuration repos use this same `toolchain_type`, which `rules_java_toolchains()` registers: - https://github.com/bazelbuild/rules_java/blob/7.9.1/toolchains/remote_java_repository.bzl#L92 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/remote_java_repository.bzl#L92 As noted earlier, bazelbuild/rules_java#210 reinstated `_allowlist_function_transition`, required by Bazel 6. However, it also included this `toolchain_type` change. (`rules_java` 7.11.0 later touched up this change for local JDK toolchain repos in:) - bazelbuild/rules_java#215: Fix bootstrap_runtime_toolchain_type reference bazelbuild/rules_java@bcc5062 This affects all toolchains defined using the `default_java_toolchain` macro, which depend upon `@rules_java//toolchains:platformclasspath`. This target, defined by the `bootclasspath` rule, depends upon `_JAVA_BOOTSTRAP_RUNTIME_TOOLCHAIN_TYPE`. - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L141 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L99 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L90 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L254-L258 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/default_java_toolchain.bzl#L304 The `rules_java` setup macro `rules_java_dependencies` depends upon `_remote_jdk_repos_for_version`. This macro wraps each remote toolchain repo instantiation in a `maybe`: - https://github.com/bazelbuild/rules_java/blob/7.6.5/java/repositories.bzl#L331-L341 The `rules_java` setup macros in the legacy `bootcamp/WORKSPACE` file instantiate the 7.10.0 toolchain repos first. This means that nothing happens when the the legacy `WORKSPACE` suffix invokes the 7.6.5 macros. This also means that all the remote JDK toolchain repos have the `toolchain_type` from 7.10.0, not from 7.6.5. `@bazel_tools//tools/jdk:toolchain_jdk_17` is an `alias` to `@rules_java//toolchains:toolchain_jdk_17`. However, Bazel maps this to the `@rules_java_builtin` repo, which is `rules_java` 7.6.5. - https://github.com/bazelbuild/bazel/blob/7.7.0/tools/jdk/BUILD.tools#L177-L178 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L271-L281 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/BUILD#L271-L281 As a result, that toolchain depends upon the `rules_java` 7.6.5 target, `@rules_java_builtin//toolchains:platformclasspath`. That target depends `@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type`. Since no existing toolchains have that `toolchain_type`, the build fails. -- `rules_java` 7.12.2 and 8.6.0 actually restored the previous `toolchain_type`; upgrading to either of those versions would also fix this build: - bazelbuild/rules_java#246: bazelbuild/rules_java@b64eb7d bazelbuild/rules_java@4206c53 --- `@bazel_tools/tools/jdk:current_java_toolchain` remains intact. It's an `alias` to `@rules_java//toolchains:current_java_toolchain`, which is a `java_toolchain_alias`. Its `toolchains` attribute contains a direct dependency on `@bazel_tools//tools/jdk:toolchain_type`, which remains the same in `rules_java` 7.10.0. - https://github.com/bazelbuild/bazel/blob/7.7.0/tools/jdk/BUILD.tools#L155 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/BUILD#L79 - https://github.com/bazelbuild/rules_java/blob/7.6.5/toolchains/java_toolchain_alias.bzl#L104 - https://github.com/bazelbuild/rules_java/blob/7.10.0/toolchains/java_toolchain_alias.bzl#L107 --- The "Bump to rules_java 7.9.0 for Bazel 7 compatibility" section of the following commit message describes my first investigation into this phenomenon. It was very close, but not exactly correct, and not as complete as the description above. - bazel-contrib/rules_scala@cd22d88 This has broken other projects in the same way: - bazelbuild/bazel: [Bazel CI] Downstream project broken by rules_java upgrade #23619 bazelbuild/bazel#23619 Bazel 8.0.0 ships with `rules_java` 8.6.1, removed `@rules_java_builtin` from the legacy `WORKSPACE` prefix, and added `@rules_java` to the suffix. - https://github.com/bazelbuild/bazel/blob/8.0.0/MODULE.bazel#L28 - bazelbuild/bazel: Remove rules_java_builtin in WORKSPACE prefix bazelbuild/bazel@7506690
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