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Removes platform/launcher contract from buildpack API spec #109

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Jul 7, 2020
Merged

Removes platform/launcher contract from buildpack API spec #109

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fdc7e17
Removes platform/launcher contract from buildpack API spec
ekcasey Jul 2, 2020
37f755e
Merge branch 'buildpack/0.3' into remove-launcher-args-from-buildpack…
nebhale Jul 7, 2020
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34 changes: 5 additions & 29 deletions buildpack.md
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Original file line number Diff line number Diff line change
Expand Up @@ -524,48 +524,24 @@ The purpose of launch is to modify the running app environment using app-provide

**GIVEN:**
- An OCI image exported by the lifecycle,
- An optional process type specified by `CNB_PROCESS_TYPE`, and
- Bash version 3 or greater, if needed,

First, the lifecycle MUST locate a start command and choose an execution strategy.

To locate a start command,

1. **IF** `CMD` in the container configuration is not empty,
**THEN** the value of `CMD` is chosen as the start command.

2. **IF** `CMD` in the container configuration is empty,
1. **IF** the `CNB_PROCESS_TYPE` environment variable is set,
1. **IF** the value of `CNB_PROCESS_TYPE` corresponds to a process in `<layers>/launch.toml`, \
**THEN** the lifecycle MUST choose the corresponding process as the start command.

2. **IF** the value of `CNB_PROCESS_TYPE` does not correspond to a process in `<layers>/launch.toml`, \
**THEN** launch fails.

2. **IF** the `CNB_PROCESS_TYPE` environment variable is not set,
1. **IF** there is a process with a `web` process type in `<layers>/launch.toml`, \
**THEN** the lifecycle MUST choose the corresponding process as the start command.

2. **IF** there is not a process with a `web` process type in `<layers>/launch.toml`, \
**THEN** launch fails.
To locate a start command, the lifecycle MUST follow the process outlined in the [Platform Interface Specification](platform.md).

To choose an execution strategy,

1. **IF** the value of `CMD` is chosen as the start command,
1. **IF** the first parameter of `CMD` is not `--`,
**THEN** the lifecycle MUST invoke the value as a command using Bash with subsequent entries as arguments.

2. **IF** the first parameter of `CMD` is `--` and the length of `CMD` is greater than one,
**THEN** the lifecycle MUST invoke the second entry using the `execve` syscall with subsequent entries as arguments.


2. **IF** a buildpack-provided process type is chosen as the start command,
1. **IF** a buildpack-provided process type is chosen as the start command,
1. **IF** the process type does not have `direct` set to `true`,
**THEN** the lifecycle MUST invoke the value of `command` as a command using Bash with values of `args` provided as arguments.

2. **IF** the process type does have `direct` set to `true`,
**THEN** the lifecycle MUST invoke the value of `command` using the `execve` syscall with values of `args` provided as arguments.

2. **IF** a user-defined process type is chosen as the start command,
**THEN** the lifecycle MUST select an execution strategy as described in the [Platform Interface Specification](platform.md).

Given the start command and execution strategy,

1. The lifecycle MUST set all buildpack-provided launch environment variables as described in the [Environment](#environment) section.
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